Portable chain saw sharpening kit with depth gauge filing attachment and method of using same

An attachment is provided for allowing a chain saw sharpener to be used for filing the depth gauge portions of the cutting links on the saw chain. The sharpener is of the type comprising a sharpener body in the form of an inverted U-shaped channel-defining member adapted to be placed over the bar of a chain saw, and a rotary burr with an abradant end portion which is receivable in a selected one of two horizontal guide bores provided in the sharpener body. The depth gauge attachment comprises an elongated gauge bar and means for removably affixing the gauge bar within the upper portion of the sharpener body channel so that the gauge bar occupies only a portion of the channel length. The thhickness of the gauge bar is such that it causes the saw chain to assume a sufficiently lower position within the sharpener body channel to bring the top of the depth gauge portion of a cutting link into contact with the abradant end portion of the rotary burr when the latter is inserted into a selected one of the two guide bores. A protective hand slide is also provided for allowing the saw chain to be manually advanced during the depth gauge filing operation.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to portable chain saw sharpening 
devices, and is particularly concerned with devices of this type in which 
the sharpener body is provided in the form of an inverted U-shaped member 
adapted to be placed over the bar of a chain saw. 
2. Description of the Prior Art 
Power-driven chain saws are widely used both for commercial purposes, as 
for example in clearing areas of land of trees and brush in preparation 
for the construction of buildings and dwellings, and for non-commercial 
purposes such as cutting firewood for home use or pruning unwanted 
branches from trees. A problem that has always confronted chain saw users, 
however, is that of maintaining the necessary degree of sharpness in the 
cutting edges of the saw chain. Without periodic sharpening, the cutting 
links of the saw chain eventually become dull with use, requiring 
additional pressure on the chain saw to effect the desired cut. A 
particular problem is presented when the teeth on one side of the saw 
chain are dull in comparison to the teeth on the other side, as often 
happens when the saw chain is brought into contact with a material other 
than wood (e.g., a nail or a piece of fence wire) during cutting. This 
condition will cause the chain saw to deviate from a straight cut, 
resulting in crooked cutting. A similar result occurs when the teeth on 
one side of the saw chain are longer than those on the other side of the 
saw chain. 
In the past, large specially-designed machines have been provided for 
sharpening the saw chain used on chain saws. However, inasmuch as these 
machines usually require removal of the saw chain from the remainder of 
the chain saw, they are rather inconvenient to use. Then, too, machines of 
this type are not always available to non-commercial or occasional users 
of chain saws, such as farmers and homeowners. For this reason, it has 
been common among such users to hand-sharpen the cutting edges of the saw 
chain using an ordinary round file. This procedure is rather tedious and 
time-consuming, particularly since the orientation of the file must 
continually be changed to accommodate the oppositely-facing cutting links 
that alternate on the saw chain. Moreover, the hand-sharpening procedure 
does not always produce uniform sharpening of all the cutting links on the 
saw chain. Another drawback of hand sharpening is that the file can etch 
longitudinal scratches on the cutting surfaces, which then tend to retain 
sap and dirt from the wood being cut. As the scratches fill, the cutting 
surfaces become dull and additional downward pressure is needed to cause 
cutting. This, in turn, gives rise to frictional heat build-up which can 
cause annealing or softening of the saw chain teeth. 
In an attempt to remedy these problems, the so-called "self-sharpening" 
chain saw has been developed. Chain saws of this type typically include a 
self-contained stone grinding wheel which is brought into contact with the 
saw chain as the latter travels around the saw bar. The inherent problem 
with this approach is that the grinding wheel is altered each time that it 
is used due to the gradual wearing away of the cutting abrasives. As a 
result, the configuration of the cutting teeth changes as the grinding 
wheel ages, and consistent and uniform sharpening of the saw chain becomes 
impossible with time. 
Perhaps the most useful kind of chain saw sharpener that has been proposed, 
at least from the standpoint of the average non-commercial user not having 
access to sophisticated sharpening machinery, is the portable chain saw 
sharpener of the type which can be attached directly to the saw bar for 
sharpening the cutting teeth when required, and then removed. Since the 
abradant sharpening element is not part of the chain saw itself, it can be 
replaced as necessary to assure a consistent degree of sharpening. 
Moreover, since sharpeners of this type usually include some sort of 
aligning or positioning fixture for the abradant sharpening element, the 
possibility of unequal sharpening as between the different cutting teeth 
on the saw chain is largely avoided. Most importantly, sharpeners of this 
type are usually compact and inexpensive devices which are economically 
attractive to non-commercial users of chain saws. 
A large variety of portable chain saw sharpeners, sometimes taking the form 
of simple filing guides or templates, have been proposed in the prior art. 
See, for example, the following United States patents: 
U.S. Pat. No. 2,594,821 
U.S. Pat. No. 2,677,289 
U.S. Pat. No. 2,755,559 
U.S. Pat. No. 2,762,241 
U.S. Pat. No. 2,770,985 
U.S. Pat. No. 2,813,438 
U.S. Pat. No. 2,871,728 
U.S. Pat. No. 3,060,768 
U.S. Pat. No. 3,071,987 
U.S. Pat. No. 3,172,306 
U.S. Pat. No. 3,172,307 
U.S. Pat. No. 3,283,615 
U.S. Pat. No. 3,438,286 
U.S. Pat. No. 3,543,612 
U.S. Pat. No. 3,670,600 
U.S. Pat. No. 3,744,349 
U.S. Pat. No. 3,889,556 
A particularly useful type of portable chain saw sharpener is disclosed in 
U.S. Pat. No. 2,770,985, to A. W. Pearce. The sharpener consists of a 
channel-shaped frame with spaced parallel walls and clamping screws for 
affixing the sharpener to the bar of a chain saw in a straddling manner. 
The walls are provided with two pairs of aligned bores arranged diagonally 
with respect to the frame. A rotatable abrading implement is removably 
engaged in one or the other of the two pairs of aligned bores to sharpen 
the saw teeth positioned between the two walls. The walls are connected by 
a web at the top of the sharpener which is provided with a sight opening 
through which the saw teeth are visible during sharpening. By engaging the 
rotary abrading implement first in one of the two pairs of aligned bores 
and then in the other, the two sets of oppositely-directed cutting teeth 
on the saw chain can be sharpened without removing the sharpener from the 
saw bar. 
Notwithstanding the utility and simplicity of the foregoing arrangement, at 
least two problems still remain. In the first place, in the absence of any 
means for positively locating the cutting link within the body of the 
sharpener prior to and during sharpening, consistent and uniform 
sharpening of all the cutting links is not assured. Moreover, the 
disclosed sharpener includes no provision for filing the depth gauge 
portions of the cutting links, which are essential in maintaining the 
proper depth to which the cutting edges penetrate the wood being cut. If 
the depth gauges are set too high, the cutting edges will be unable to 
penetrate sufficiently, requiring increased downward pressure on the chain 
saw to enable cutting. If they are set too low, the penetration of the 
cutting edges into the wood will be too great, causing grabbing and 
jerking of the chain saw. 
More recently, in U.S. Pat. No. 3,744,349, to A. A. Juncker, a portable 
chain saw sharpener has been proposed in which the guide bores are 
provided in a movable carriage mounted on one side of the sharpener frame, 
rather than in the form of pairs of aligned bores penetrating both side 
walls of the sharpener as in U.S. Pat. No. 2,770,985. A system of guide 
bars and screws is provided in the device of U.S. Pat. No. 3,744,349 to 
allow adjustment of the carriage in both the horizontal and vertical 
directions. In addition to the two clamping screws used for affixing the 
sharpener body to the bar of the chain saw, a third clamping screw is 
provided for securing a chain tooth temporarily relative to the sharpener 
frame. Once the tooth is clamped in position, the end of a tapered carbide 
steel file is inserted into one of the guide bores and the carriage is 
adjusted until the file touches the edge of the tooth. The carriage is 
then locked in position and sharpening is carried out by advancing the 
file, which now is rotated by a power drill, across the front of the tooth 
and back. The next tooth is then advanced to the same position, which is 
established by an adjustable stop means in the form of a reversely-bent 
leaf spring protruding into the sharpening area. The sharpening operation 
is then repeated. When all of the teeth facing in one direction have been 
sharpened, the file is inserted in the second guide bore and the process 
is repeated for the teeth facing in the other direction. In order to allow 
for grinding of the depth gauges, the carriage is provided with a third 
guide bore disposed above the first two. After sharpening, a further 
adjustment of the carriage is made to bring the third guide bore into 
alignment with the depth gauge of the first tooth, whereupon the turning 
file is inserted into the third guide bore to grind the depth gauge to the 
desired level. This operation is then repeated for the depth gauges of the 
remaining teeth. 
Although the sharpener described by U.S. Pat. No. 3,744,349 possesses the 
undeniable advantage of combining the sharpening and depth gauge filing 
functions in a single device, there are several disadvantages inherent in 
its design and its intended manner of operation. In the first place, the 
need for a movable carriage to adjust the position of the guide bores adds 
an undesireable degree of complexity to the device, as compared to the 
essentially unitary sharpeners of the type described, for example, by the 
previously-noted U.S. Pat. No. 2,770,985. Further, the described procedure 
of using the carbide steel file for adjusting the position of the guide 
bores relative to the cutting teeth, relying as it does on bringing the 
tooth into registry with some point on the gradually tapering end of the 
file, is inherently imprecise. The amount of sharpening will clearly 
depend upon how far the tapered file is inserted into the guide bore 
during the adjustment procedure, which is determined simply by visual 
approximation. If the approximation is incorrect, either too much or too 
little material will be removed from the cutting edge of the tooth during 
sharpening, and the adjustment must be repeated. Although the movable 
carriage assembly would no doubt facilitate such repeated adjustments, the 
adjustment procedure is still rather tedious and time consuming, since it 
amounts essentially to a trail-and-error process. Finally, and perhaps 
most importantly, the use of the file for adjusting the relative positions 
of the guide bores and the cutting teeth creates the risk of damage to the 
brittle carbide material of which the file is made. Such damage might 
occur, for example, as a result of inadvertently striking the file against 
the edge of a cutting tooth that is positioned too close to the guide bore 
before the adjustment is made. To the extent that such damage might 
necessitate premature replacement of the file, the user of the sharpener 
will be put to an additional and undesirable expense. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a portable chain saw sharpening 
kit comprises a sharpener body in the form of an inverted U-shaped 
channel-defining member adapted to be placed over the bar of a chain saw, 
said sharpener body being provided with an opening therein exposing a 
portion of the channel and with first and second guide bores converging 
toward each other at equal angles with respect to a line perpendicular to 
the channel axis; first clamping means for clamping a cutting link in a 
selected position within said sharpener body; second clamping means for 
clamping the sharpener body to the bar of a chain saw; a rotary burr 
receivable in a selected one of the first and second guide bores, said 
rotary burr having an abradant end portion for sharpening a cutting link 
positioned within the sharpener body; and an alignment pin receivable in a 
selected one of said first and second guide bores for aligning a cutting 
link within the sharpener body prior to sharpening. The alignment pin 
comprises a shank portion and a reduced end portion for abutting against 
the edge of the cutting link to be sharpened, said reduced end portion 
being dimensioned to allow for the removal of a predetermined amount of 
material from the edge of the cutting link when the rotary burr is 
subsequently inserted into the selected guide bore for sharpening. 
In a preferred embodiment of the invention, the shank portion and the 
reduced end portion of the alignment pin are both circular in 
cross-section but have different diameters. Preferably also, the reduced 
end portion of the alignment pin is eccentrically offset from the shank 
portion of the alignment pin, and means are provided for rotationally 
positioning the alignment pin within a selected one of the first and 
second guide bores in the sharpener body. In a particularly preferred 
embodiment of the invention, the alignment pin includes an enlarged head 
portion on the end of the shank portion opposite to the reduced end 
portion, and the aforesaid rotational positioning means comprises a 
projection on the underside of the head portion for engaging corresponding 
notches formed on the sharpener body. Where the reduced end portion of the 
alignment pin is eccentrically offset from the shank portion, as in the 
preferred embodiment, the reduced end portion preferably has a diameter 
substantially equal to the widest diameter of the abradant end portion of 
the rotary burr. 
The use of the aforesaid alignment pin provides a number of distinct 
advantages over the prior art. In the first place, it avoids the necessity 
of using the rotary burr itself as the means for adjusting the position of 
the saw chain cutting links within the channel of the sharpener body, and 
therefore avoids the possible damage to the burr that may occur during 
this procedure. If a cutting link is positioned too close to the selected 
guide bore before the adjustment is made, it is the alignment pin (rather 
than the burr) that strikes the improperly positioned cutting link. By the 
time the rotary burr is inserted, the cutting link is in the proper 
position and the burr engages the cutting link only to the extent required 
for proper sharpening. 
The alignment pin also allows the cutting link position to be adjusted more 
precisely, and with less effort, than would be possible by using the 
rotary burr for this purpose. As noted earlier, the prior art procedure 
for positioning the cutting links using the rotary burr requires that the 
cutting link be brought into contact with some point on the tapered end of 
the burr, as by partial insertion of the burr into the guide bore. When 
the burr is then fully inserted into the guide bore for sharpening, the 
amount of material removed from the sharpened edge of the cutting link 
will depend upon the difference between the maximum diameter of the burr 
and its diameter at the point on its tapered end that was brought into 
contact with the cutting link during the adjustment procedure. The latter 
point, having been selected simply by visual approximation from various 
other possible points on the gradually tapered end of the burr, will not 
necessarily be accurate enough to assure the proper amount of sharpening. 
As a result, either too much or too little material will be removed from 
the edge of the cutting link during sharpening. The adjustment must 
therefore be repeated until the proper amount of sharpening is obtained. 
This is essentially a trial-and-error procedure and, although it can be 
facilitated by a movable carriage assembly as provided in the prior art, 
it is nevertheless a rather tedious and time-consuming operation. The use 
of the alignment pin as provided in the present invention eliminates these 
disadvantages. Since the reduced end of the alignment pin is properly 
dimensioned relative to the burr diameter to provide the proper amount of 
sharpening, the position of the cutting link within the sharpener body can 
be accurately adjusted the first time, without the need for subsequent 
fine adjustments. As a result, there is no requirement for a movable 
carriage assembly or the like, and the sharpener body can therefore be 
provided as a unitary structure which is simple to use and inexpensive to 
manufacture. 
In accordance with another important aspect of the present invention, the 
sharpener is provided with a depth gauge attachment for allowing the 
rotary burr to be used for filing the depth gauges of a cutting link. The 
depth gauge attachment comprises an elongated gauge bar shaped and 
dimensioned to be received in the upper part of the channel of the 
sharpener body, and means for removably affixing the gauge bar within the 
upper part of the channel. The gauge bar is provided with a flat surface 
on the underside thereof to provide a guide surface for the upper portions 
of the cutting links on the saw chain, with the thickness of the gauge bar 
being selected to cause the saw chain to assume a sufficiently lower 
position within the channel of the sharpner body to bring the top of the 
depth gauge portions of the cutting links into contact with the abradant 
end portion of the rotary burr when the rotary burr is inserted into one 
of the two guide bores in the sharpener body. The gauge bar is affixed in 
the upper portion of the sharpener body channel in a manner such that the 
guage bar occupies only a portion of the channel length, said portion not 
including the area immediately adjacent to the open end of the guide bore 
in which the rotary burr is inserted. Preferably, the gauge bar is of 
sufficient length to protrude beyond one end of the channel in the 
sharpener body when affixed therein, with the protruding portion of the 
gauge bar thereby forming a guide for the saw chain outside the sharpener 
body. 
In a preferred embodiment of the invention, the top of the sharpener body 
is provided with a through-hole which opens into the sharpener body 
channel, and the gauge bar is provided with a threaded bore at a point 
along its length. The means for removably affixing the gauge bar within 
the upper portion of the sharpener body channel may then comprise a 
threaded fastener adapted to be loosely received through the through-hole 
in the top of the sharpener body and to be threadably engaged with the 
threaded bore in the gauge bar. The threaded fastener is provided with an 
enlarged head portion at one end thereof for bearing against the top of 
the sharpener body in order to bring the gauge bar into abutting contact 
with the upper portion of the sharpener body channel. In order to assure a 
smooth mechanical fit, the longitudinal edges of the gauge bar are 
preferably beveled, and the upper interior longitudinal edges of the 
sharpener body channel are preferably rounded in a manner complementing 
the beveled edges of the gauge bar. 
The aforesaid depth gauge attachment provides a simple yet effective means 
for adapting the basic sharpener assembly for use in filing the depth 
gauge portions of the saw chain cutting links after the sharpening 
operation has been completed. A particularly important advantage of the 
depth gauge attachment is that it does not require any modification of the 
basic sharpener assembly, other than the provision of a simple 
through-hole in the top of the sharpener body to accommodate the threaded 
fastener by which the gauge bar is held in position within the sharpener 
body channel. As a result, the manufacturer need only provide one version 
of the basic sharpener assembly, which can be sold with or without the 
depth gauge attachment. If the purchaser of the basic sharpener later has 
a need for the depth gauge attachment, this can be purchased separately 
and readily attached to the originally-purchased sharpener. 
The sharpener of the present invention may also be provided with adjustable 
stop means, usable during the sharpening operation but not needed during 
the depth gauge filing operation, said adjustable stop means being 
attachable to the sharpener body in lieu of the depth gauge attachment. 
The stop means comprises, in particular, a pawl member supported on the 
top of the sharpener body and extending downwardly through the opening in 
the sharpener body into the sharpener body channel, and means for 
adjustably mounting the pawl member on the top of the sharpener body for 
selective movement along the direction of the sharpener body channel. The 
pawl member is arranged to abut the rear portion of a cutting link located 
within the sharpener body channel in order to position the cutting link 
relative to the open end of a selected one of the two guide bores in the 
sharpener body, and is further arranged to be freely pivotable in one 
direction and restrained against movement in the other direction. The 
means for adjustably mounting the pawl member on the top of the sharpener 
body comprises a substantially U-shaped member disposed horizontally on 
top of the sharpener body and a clamping screw which passes through the 
open central portion of the U-shaped member and is threadably received in 
the through-hole provided in the top of the sharpener body for clamping 
the U-shaped member in a selected position along the top of the sharpener 
body. The pawl member is pivotally supported at the open end of the 
U-shaped member and extends downwardly therefrom through the opening in 
the sharpener body and into the sharpener body channel. 
In accordance with an important feature of the invention, the sharpener 
body is provided with a raised boss which is engageable with the open 
central portion of the U-shaped member for guiding the motion of the 
U-shaped member in a direction parallel to the axis of the sharpener body 
channel. To facilitate this guiding function, the raised boss is 
preferably elongated in a direction parallel to the axis of the sharpener 
body channel. The raised boss also prevents possible shifting of the 
U-shaped member about the clamping screw while the sharpener is in use. 
By providing for alternative attachment of 1he depth gauge attachment or 
the stop means, the latter not being required during the depth gauge 
filing operation, the sharpener need only carry, at any given time, the 
minimum number of parts required for performing the job at hand. This is 
an advantage from the standpoint of portability as well as simplicity. 
However, it is within the scope of the invention to provide the sharpener 
only with the stop means and not the depth gauge attachment, or 
vice-versa, since it is conceivable that some purchasers of the sharpener 
may have a need for one and not the other. In that event, it is still 
advantageous to provide for interchangeable attachment of the stop means 
and the depth gauge attachment to the sharpener body, as in the preferred 
embodiment, since this eliminates the need to manufacture a different type 
of sharpener body for each purpose. 
In accordance with a further aspect of the invention, a protective hand 
slide is provided for manual engagement with the bar of a chain saw on the 
side opposite to that on which the sharpener body is placed. The 
protective hand slide preferably comprises an elongated handle member 
adapted to be placed against the edge of the saw bar, said handle member 
having a longitudinal channel therein for receiving the saw chain and a 
transversely-mounted pin within said channel for engaging a cutting link 
of the chain saw. The handle member preferably includes enlarged portions 
at each end thereof on the side opposite the channel of the handle member 
in order to prevent the user's hand from inadvertently slipping off the 
protective hand slide. The hand slide allows the user to manually advance 
the saw chain around the bar while using the sharpener of the present 
invention, without the the risk of injury from the sharpened cutting edges 
of the cutting links. Although the protective hand slide is intended 
primarily for use during the depth gauge filing operation, it can also be 
used to advance the next cutting link into position between sharpening 
operations. 
The present invention also comprehends a method for using an alignment pin 
of the type described herein, and a method for using a depth gauge 
attachment of the type described herein, as will become apparent from the 
detailed description to follow.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
A section of a type of saw chain which is commonly used on power-driven 
chain saws is illustrated in FIG. 1. In the interest of clarity, the saw 
chain 20 is shown removed from the bar of the chain saw. The saw chain 20 
comprises a series of right-hand cutting links 22 and left-hand cutting 
links 24, alternately positioned on the chain. Each cutting link is made 
up of two operative portions, specifically, a curved cutting portion 26 
which defines a curved cutting edge 28, and an upstanding projection 30 in 
front of the cutting edge which is usually referred to as a depth gauge. 
The cutting edges are ground at a predetermined rake angle, typically 
35.degree., with respect to a line drawn perpendicular to the length of 
the cutting link. When the chain saw is in use, the depth gauge 30 leads 
the cutting edge 28 into the wood and determines the depth of penetration 
of the cutting edge into the wood. The saw chain 20 also includes drive 
links 32 which are engaged by the sprocket of the chain saw in order to 
propel the chain around the saw bar. The edge of the saw bar is ordinarily 
provided with a channel for receiving the lower portions of the drive 
links 32, thereby maintaining the saw chain 20 in position along the 
periphery of the bar. The drive links 32 and cutting links 22, 24 are 
interconnected by tie straps 34 and rivets 36, as shown, to form a 
continuous chain which extends around the saw bar in an endless loop. The 
foregoing details of the saw chain 20 are conventional and form no part of 
the present invention. 
The chain saw sharpening kit of the present invention will now be described 
with reference to FIGS. 2-6. In FIG. 2, the basic sharpening kit is 
illustrated in an exploded perspective view in order to illustrate the 
various components thereof. FIGS. 3, 4, 5 and 6 illustrate the assembled 
sharpening kit in a left side elevational view, front elevational view, 
right side elevational view, and plan view, respectively, with a portion 
of the saw bar being shown in each case to illrustate the manner in which 
the sharpener is mounted thereon. 
As best seen in FIG. 2, the sharpening kit includes a unitary sharpener 
body 38 in the form of a channel member adapted to be placed over the bar 
of a chain saw. The sharpener body 38 includes a U-shaped portion which 
comprises an upper web including end portions 40 and 41, first and second 
spaced-apart, parallel side walls 42 and 44, respectively, which extend 
downwardly from the upper web 40, 41 to define a channel 46 therebetween, 
and a horizontal extension 48 projecting outwardly from the second side 
wall 44 on the side opposite the channel 46. Adjoining central portions of 
the upper web 40, 41 and first side wall 42 are cut away, as shown, to 
define an open viewing area 50 near the center of the channel 46 for 
receiving a cutting link of the saw chain to be sharpened. The horizontal 
extension 48 is provided with first and second horizontal guide bores 52 
and 54, respectively, which extend from opposite corners of the horizontal 
extension 48 and open through the second side wall 44 into the open 
cutting link receiving area 50 of the channel 46. The corners 49 and 51 of 
the horizontal extension 48 are flattened, as shown, to accommodate the 
openings of the guide bores 52 and 54, respectively, and are provided with 
notches 53, 55 for a purpose to be described hereinafter. 
As will be more clearly apparent from the plan view of FIG. 6, the guide 
bores 52 and 54 converge toward each other as they approach the channel 
46, and are inclined at equal angles with respect to a line perpendicular 
to the channel axis. The inclination angle of each of the guide bores 52 
and 54 is preferably 35.degree. to match the rake angle of the cutting 
edges on the right- and left-hand cutting links 22 and 24 in FIG. 1. The 
flattened corners 49, 51 of the horizontal extension 48 lie in planes 
perpendicular to the axes of the respective guide bores 52, 54, whereby 
these planes diverge outwardly in the direction of the channel 46 at equal 
55.degree. angles with respect to a line perpendicular to the channel 
axis. Thus, the flattened corners 49, 51 are each inclined at an angle of 
35.degree. relative to the outer edge 47 of the horizontal extention 48. 
Referring again to FIG. 2, a threaded bore 56 is provided in the first side 
wall 42 of the sharpener body at a point below the open cutting link 
receiving area 50 for receiving a first clamping screw 58. The clamping 
screw 58 functions to exert clamping pressure against a cutting link which 
is positioned with the open area 50 of the channel 46 at a point adjacent 
to the open ends of the guide bores 52 and 54. The cutting link is thereby 
clamped against the interior surface 45 of the second side wall 44 in a 
position appropriate for sharpening, as shown in FIGS. 4 and 6. The 
clamping function of the clamping screw 58 is assisted by the provision of 
a flexible clamping strip 60, which may be made from spring-tempered steel 
or some other suitable material. As shown most clearly in FIGS. 2 and 4, 
the flexible clamping strip 60 is bent into a U-shape with one leg 62 made 
longer than the other leg 64, and is attached to the bottom edge of the 
side wall 42 with longer leg 62 extending upwardly along the inside 
surface of the side wall 42 to a point just above the lower edge of the 
open area 50. When the clamping screw 58 is advanced into the threaded 
bore 56, the end of the clamping screw 58 is brought to bear against the 
leg 62 of the clamping strip, which in turn bears against the side of the 
cutting link to be sharpened. The upper corners 66, 68 of the longer leg 
62 of the clamping strip are bent inward slightly, as shown, in order to 
facilitate movement of the saw chain through the sharpener body channel 46 
between sharpening operations. As shown in FIG. 2, the shorter leg 64 of 
the clamping strip is provided with a hole 70 which is aligned with a 
threaded bore 72 formed in the first side wall 42 of the sharpener body 38 
at a point below the threaded bore 56. A screw 74 passes through the hole 
70 and is engaged with the threaded bore 72 in order to attach the 
clamping strip 60 to the sharpener body. A lock washer 76 is interposed 
between the head of the screw 74 and the shorter leg 64 of the clamping 
strip to insure that the screw 74 remains securely engaged in the threaded 
bore 72. 
The flexible clamping strip 60 may be omitted, if desired, but its 
inclusion is advantageous since it presents a broad clamping surface for 
abutting against the side of the cutting link to be sharpened. This is 
desirable not only because it enhances the frictional clamping action of 
the clamping screw 58, but also because it is capable of exerting firm 
clamping pressure against any part of the cutting link to be sharpened. 
If, on the other hand, the clamping strip 60 is eliminated and the end of 
the clamping screw 58 is brought to bear directly against the side of the 
cutting link, the possibility exists that the end of the clamping screw 
may be brought into contact with a non-smooth portion of the cutting link 
(e.g., with one of the rivets 36 in FIG. 1) from which the clamping screw 
might easily disengage during the sharpening operation. As a result, the 
cutting link may become dislodged from its proper sharpening position 
relative to the openings of the guide bores 52 and 54. This possibility is 
substantially prevented by the use of the flexible clamping strip 60, 
which presents a large enough clamping surface to the cutting link to 
assure that the cutting link cannot become inadvertently dislodged in this 
way. 
With continued reference to FIGS. 2-6, the first side wall 42 of the 
sharpener body is provided with two additional threaded bores 78, 80 
(visible in FIG. 2) at points near the lower corners of the wall 42, these 
additional bores being located below the level of the threaded bore 56 
which receives the first clamping screw 58. Second and third clamping 
screws 82 and 84 are received in the threaded bores 78 and 80, 
respectively, for the purpose of bearing against the bar 85 of the chain 
saw and thereby clamping the sharpener body 38 as a whole to the saw bar, 
as shown in FIGS. 3-6. Since the surface of the saw bar is smooth, unlike 
the side of the saw chain, the clamping strip 60 which is provided for the 
clamping screw 58 is not required for either of the clamping screws 82, 
84. All three clamping screws 58, 82 and 84 are provided with knurled 
heads, as shown, so that they may be conveniently manipulated by the user 
of the sharpener. 
With the sharpener body 38 mounted and clamped to the saw bar 58 is 
illustrated in FIGS. 3-6, the saw chain 20 faces and abuts the underside 
of the upper web 40, 41, and the cutting link 22 to be sharpened is 
located in the open viewing area 50 of the sharpener body. After a 
necessary adjustment procedure, carried out in connection with the 
alignment or set-up pin 116 as will be described hereinafter, sharpening 
may be accomplished by means of the rotary burr 86. The rotary burr 86 is 
capable of being inserted into either one of the two horizontal guide 
bores 52 and 54, depending upon whether a right-hand cutting link 22 or a 
left-hand cutting link 24 is to be sharpened. As will be described 
hereinafter, the rotary burr 86 will normally be retained in one of the 
two guide bores 52, 54 to sharpen in sequence all the cutting links of one 
type (e.g., all right-hand cutting links), and will then be inserted into 
the other guide bore to sequentially sharpen all the remaining cutting 
links (e.g., all left-hand cutting links). 
The rotary burr 86 is preferably made from a single piece of tungsten 
carbide or some other material of suitable hardness and durability, such 
as hardened steel. The rotary burr 86 is machined to provide a tapered 
abradant portion 88 at one end thereof and a smooth shank portion 90 at 
the other end, the latter portion being rigidly affixed to a hand crank 
92. The abradant end portion 88 of the rotary burr 86 preferably takes the 
form of a helical pattern of machined cutting ridges, as shown, but may be 
machined in any other desired configuration (e.g., a cross-hatch pattern) 
which provides a suitable sharpening surface. Alternatively, the abradant 
end portion of the burr may comprise a layer or a solid body of abrasive 
material of the type used in grinding wheels and grindstones to provide a 
sharpening surface. As used herein, the term "abradant end portion" as 
applied to the rotary burr will be understood to include any of the 
foregoing types of sharpening surfaces, or their equivalents. 
The smooth shank portion 90 of the rotary burr 86 is preferably affixed to 
the hand crank 92 by means of a recessed Allen-head set screw 91 (visible 
in FIGS. 4 and 5) so that the burr 86 can be replaced when the abradant 
end portion 88 becomes worn or damaged, without replacing the handle 92. A 
swivel pin 94 (visible in FIGS. 3 and 6) with an enlarged head 96 is 
rigidly mounted in the hand crank 92 at the end remote from the burr 86 
for supporting a freely rotatable swivel-type handle 98. The handle 98 is 
preferably cylindrical with a slight inward taper toward the main part of 
the hand crank 92, as shown, so that it can be conveniently grasped by the 
user of the sharpener to impart rotation to the hand crank 92 and thereby 
to the rotary burr 86. 
It should be noted that it is within the scope of the invention to employ 
means other than the hand crank 92 to turn the rotary burr 86. Thus, for 
example, the shank portion 90 of the rotary burr may be inserted into the 
chuck of an electric hand drill to obtain powered operation of the burr. 
The hand crank 92 is preferred, however, since it eliminates the need for 
separate power equipment and allows the sharpening kit to be used at job 
sites where electric power is unavailable. 
With further reference to FIGS. 2-6, the sharpening kit is also provided 
with adjustable stop means, in the form of an L-shaped pawl member 100, 
for abutting the rear portion of a cutting link located within the open 
area 50 of the sharpener body channel 46. As will be described 
hereinafter, the pawl member 100 functions to position the successive 
cutting links with respect to the openings of the guide bores 52, 54 in 
the second side wall 44 of the sharpener body 38. To this end, the pawl 
member 100 is supported on one end portion 41 of the upper web of the 
sharpener body 38 by means of a U-shaped member 102, and extends 
downwardly into the open area 50 of the sharpener body channel 46 where 
the cutting link is positioned for sharpening. The pawl member 100 is 
pivotally supported at the open end of the U-shaped member 102 by means of 
a pivot pin 104, and is freely pivotable in a direction away from the end 
portion 41 of the upper web on which the U-shaped member 102 is mounted 
(i.e., in a counter-clockwise direction as viewed in FIG. 3). The pawl 
member 100 is prevented from pivoting in the opposite direction by means 
of a small cross-member or shelf 106 (shown in phantom in FIGS. 2, 3 and 
6) which is formed across the bottom part of the open end of the U-shaped 
member 102, preferably as an integral part thereof. In this way, the pawl 
member 100 will normally rest in the downwardly-extending position shown 
in FIGS. 2 and 3, and will be restrained against movement in a direction 
toward the end portion 41 of the upper web on which the U-shaped member 
102 is mounted. 
In order to allow adjustment of the position of the pawl member 100, the 
U-shaped member 102 is removably affixed to the upper web 40 by means of a 
clamping screw 108. The clamping screw 108 passes through the open central 
portion of the U-shaped member 102, and its end is received in a threaded 
bore 110 which is provided in the end portion 41 of the upper web of the 
sharpener body. When the clamping screw 108 is installed and tightened, as 
shown in FIGS. 3-6, the U-shaped member 108 is clamped horizontally 
between the enlarged head 112 of the clamping screw 108 and the upper 
surface of the end portion 41 of the upper web, thereby maintaining the 
U-shaped member 108 in a selected position along the end portion 41 of the 
upper web. This position can be adjusted by loosening the clamping screw 
108, sliding the U-shaped member in a direction toward or away from the 
end portion 41 of the upper web, and then retightening the clamping screw 
108. The enlarged head 112 of the clamping screw 108 is preferably 
knurled, as shown, to facilitate manual loosening and retightening. The 
result of the aforesaid adjustment is to move the pawl member 100 either 
toward or away from the end portion 41 of the upper web within the open 
area 50 of the sharpener body channel, such movement occurring in a 
direction parallel to the axis of the sharpener body channel 46. 
In order to guide the U-shaped member 102 in its sliding movement along the 
top of the sharpener body, a raised boss 114 is provided on the top 
surface at the upper web portion 41 for engagement with the open central 
portion of the U-shaped member 102. The raised boss 114 is located 
adjacent to the threaded bore 110 and is aligned therewith in the 
direction of the sharpener body channel 46. As a result, the boss 114 and 
clamping screw 108 cooperate to restrict the sliding motion of the 
U-shaped member 102 to a direction parallel to the axis of the sharpener 
body channel 46. The raised boss 114 is preferably elongated in a 
direction parallel to the channel axis, as shown, in order to allow smooth 
engagement with the parallel interior side surfaces of the open central 
portion of the U-shaped member 102. In addition to guiding the sliding 
motion of the U-shaped member 102 during adjustment of the position of 
pawl member 100, the raised boss 114 also functions to prevent possible 
rotational shifting of the U-shaped member 102 around the clamping screw 
108 after the latter has been tightened. Such rotational shifting of the 
U-shaped member 102 might otherwise result in gradual dislodgement of the 
pawl member 100 from its adjusted position during sharpening. It will be 
apparent that, without the raised boss 114, such rotational shifting of 
the U-shaped member 102 would be possible, at least to a limited extent, 
whenever the pawl member 100 has been adjusted to a position at which it 
is separated from the inner edge of the end portion 41 of the upper web of 
the sharpener body. This undesirable result is prevented by the provision 
of the raised boss 114, which is maintained in locking engagement with the 
open central portion of the U-shaped member 102 when the clamping screw 
108 has been tightened. 
In accordance with an important feature of the present invention, the chain 
saw sharpening kit is further provided with an alignment or set-up pin 
116, the function of which will now be described. The alignment pin 
comprises, in general, a shank portion 118 and a reduced end portion 120. 
The shank portion 118 is dimensioned for smooth insertion into either one 
of the two guide bores 52, 54 in lieu of the rotary burr 86, and will 
usually have a diameter appproximately equal to that of the shank portion 
90 of the rotary burr. When the alignment pin 116 is fully inserted into 
one of the guide bores 52, 54, the reduced end portion 120 allows a 
cutting link of the saw chain to be positioned within the channel 46 of 
the sharpener body such that when the rotary burr 86 is subsequently 
inserted into the guide bore and turned, the amount of material removed 
from the cutting link by the abradant end portion 88 of the burr will be 
exactly the amount necessary to produce a properly sharpened edge. The 
alignment pin 116 is also provided with an enlarged head portion 122 which 
is brought into contact with one of the flattened corners 49, 51 of the 
sharpener body extension 48 when the alignment pin is fully inserted into 
the corresponding one of the guide bores 52, 54. The head portion 122 thus 
defines the full extent of the insertion of the alignment pin into the 
guide bores 52, 54, and also performs a rotational positioning function as 
will be described hereinafter. 
The details of the alignment pin 116 will be more readily apprehended from 
the enlarged views of FIGS. 7 and 8, which illustrate the alignment pin in 
a perspective view and an end view, respectively. It will be seen that the 
shank portion 118 and reduced end portion 120 of the alignment pin 116 are 
both circular in cross-section, with the diameter of the reduced end 
portion 120 being somewhat smaller than that of the shank portion 118. As 
noted earlier, the diameter of the shank portion 118 of the alignment pin 
is preferably equal to the diameter of the smooth shank portion 90 of the 
rotary burr 86, since both devices are intended to fit smoothly and 
interchangeably into the guide bores 52 and 54 of the sharpener body 38. 
With reference to the end view of FIG. 8, which is taken from the reduced 
end portion of the alignment pin 116, it can be seen that the reduced end 
portion 120 is eccentrically offset from the shank portion 118 both 
horizontally and, to a lesser extent, vertically. In FIG. 8, therefore, 
the axis of the reduced end portion 120 is displaced to the right of, and 
slightly above, the axis of the shank portion 118 of the alignment pin. In 
practice, the amount of horizontal displacement of the axis of the reduced 
end portion 120 from the axis of the shank portion 118 is about 0.015 
inch, and the amount of vertical displacement of the axis of the reduced 
end portion 120 from the axis of the shank portion 118 is about 0.004 
inch. These displacements or offset distances are indicated by the 
reference numerals 128 and 129, respectively, in FIG. 8. This provides, 
with reference to FIG. 8, an inset portion 124 (outlined in phantom) 
across the lower and left-hand portions of the pin where the radial 
spacing between the reduced end portion 120 and the shank portion 118 is 
greater than it would have been if the reduced end portion 120 and shank 
portion 118 were precisely concentric. The inset portion 124 extends 
half-way around the reduced end portion 120 of the alignment pin and 
serves as an abutment surface for the forward edge of the cutting link to 
be sharpened. In order to assure that the inset portion 124 is brought 
into proper alignment with the forward edge of the cutting link, a rib or 
projection 126 is provided on the underside of the enlarged head 122 of 
the alignment pin 116. The projection extends radially inward from the 
edge of the head 122 of the alignment pin 116 and adjoins the shank 
portion 118, as shown. When the alignment pin 116 is inserted into one of 
the two guide bores 52, 54 of the sharpener body 38, the projection 126 
engages the corresponding one of the notches 53, 55 (shown in FIG. 2) and 
thereby brings the alignment pin into the rotational position shown in 
FIG. 8. This assures that the inset portion 124 faces toward the forward 
edge of the cutting link in the open area 50 of the sharpener body 
channel. If it is assumed that the projection 126 defines the 0.degree. 
position in FIG. 8, then the closest approach between the periphery of the 
shank portion 118 and the periphery of the reduced end portion 120 will 
occur at about the 75.degree. point, and the inset portion 124 will extend 
approximately between the 165.degree. and 345.degree. points. 
Referring back momentarily to FIGS. 2 and 6, it will be seen that abradant 
end portion 88 of the rotary burr 86 has what might be described as a 
"candle-flame" shape, tapering from a portion 87 of maximum or widest 
diameter in the area adjacent to the smooth shank portion 90 to an end 
region 89 of minimum diameter. When the rotary burr 86 is inserted into 
one of the guide bores 52, 54 of the sharpener body and rotated, the 
maximum-diameter region 87 of the abradant end portion 88 will eventually 
reach the edge of the cutting link being sharpened and will determine how 
much material is removed from the cutting edge during sharpening. 
Referring again to FIGS. 7 and 8, the diameter of the reduced end portion 
120 of the alignment pin 116 is preferably made substantially equal to 
that of the maximum-diameter portion 87 of the abradant end 88 of the 
rotary burr. If it is supposed for a moment that the shank portion 118 and 
reduced end portion 120 of the alignment pin are arranged concentrically 
(rather than eccentrically), and that the position of a cutting link is 
adjusted by bringing its cutting edge 28 (FIG. 1) into abutting contact 
with the reduced end portion of the alignment pin after the latter has 
been inserted into the appropriate one of the guide bores 52 and 54, it is 
apparent that subsequent insertion of the rotary burr 86 into the guide 
bore will cause the widest part 87 of its abradant end portion 88 to just 
touch the cutting edge 28 of the cutting link. In this hypothetical 
situation, no sharpening would occur. However, with the reduced end 
portion 120 of the alignment pin eccentrically offset from the shank 
portion 18, as shown in FIG. 8, a different result obtains. In particular, 
when the alignment pin is inserted into one of the two guide bores 52, 54, 
with the projection 126 engaged with the corresponding one of the notches 
53, 55 in the sharpener body 38, the inset portion 124 on the reduced end 
portion 120 of the alignment pin will be presented to the cutting edge 28 
of the cutting link to be sharpened. If the cutting edge 28 of the cutting 
link is now brought into abutting contact with that part of the reduced 
end portion of the alignment pin, it will occupy a position slightly 
beyond the position it would have occupied if the reduced end portion 120 
and shank portion 118 of the alignment pin were exactly coaxial or 
concentric. As a result, when the alignment pin 116 is removed and the 
rotary burr 86 is inserted and rotated, and abradant end portion 88 of the 
rotary burr 86 will bear against the cutting edge 28 of the cutting link 
and remove a certain amount of material therefrom, thereby resulting in a 
sharpened cutting edge. Referring to FIG. 8, and recalling that the 
diameter of the reduced end portion 120 of the alignment pin 116 is 
preferably made equal to the diameter of the widest portion 87 of the 
abradant end portion 88 of the rotary burr 86, it will be apparent that 
the amount of material removed from the cutting edge 28 during sharpening 
will be determined by the amount of horizontal and vertical offset between 
the axis of the reduced end portion 120 of the alignment pin 116 and the 
axis of the shank portion 118. These offset distances are, as noted 
earlier, indicated by the reference numerals 128 and 129 in FIG. 8. Thus, 
by virtue of the alignment pin 116, only the proper amount of material 
will be removed from the cutting edges 28 of the cutting links during 
sharpening. 
The manner in which the chain saw sharpening kit of the present invention 
may be used to sharpen the cutting links of a chain saw will now be 
described with reference to FIGS. 2-6. With all clamping screws 58, 82, 84 
and 108 loosened, and with the pawl member 100 withdrawn fully to the edge 
of the end portion 41 of the upper web, the sharpener body 38 is placed 
over the bar 85 of the chain saw in a straddling manner as illustrated in 
FIGS. 3-6. At this point, the rotary burr 85 is not yet inserted into 
either of the guide bores 52 and 54. The alignment pin 116 is now inserted 
fully into one of the two guide bores, which will be assumed to be the 
guide bore 52 for the purpose of example, and the projection 126 on the 
alignment pin is brought into engagement with the notch 53 on the 
sharpener body. The sharpener body 38 is now moved bodily until the 
reduced end portion 120 of the alignment pin rests against the cutting 
edge 28 of the cutting link to be sharpened, which will be a right-hand 
cutting link 22 as shown in FIG. 1. The two outer clamping screws 82 and 
84 are now tightened to clamp the sharpener body 38 to the bar 85 of the 
chain saw. The middle clamping screw 58 is then tightened to cause the 
flexible clamping strip 60 to bear against the side of the cutting link 22 
which is to be sharpened. The U-shaped support member 102 is now moved 
forward along the end portion 41 of the upper web of the sharpener body in 
order to bring the lower end of depending pawl member 100 into contact 
with the back edge of the cutting link 22, as shown in FIG. 3. The 
clamping screw 108 is then tightened to lock the U-shaped support member 
102, and hence the pawl member 100, in position. The middle clamp screw 58 
is then loosened and the alignement pin 116 is removed from the guide bore 
52. 
With the sharpener now prepared for sharpening, the middle clamp screw 58 
is retightened to clamp the first cutting link 22 in position relative to 
the guide bore 52. The rotary burr is then inserted into the guide bore 52 
and rotated, by means of the hand crank 92, in a clockwise direction as 
shown in FIG. 5. As the hand crank 92 is turned, the abradant end portion 
88 of the rotary burr advances into the open area 50 of the sharpener body 
channel and thereby sharpens the cutting edge 28 of the cutting link 22. 
When the base of the hand crank touches the flattened corner 49 of the 
sharpener body, as shown in FIG. 6, sharpening is completed and the rotary 
burr 86 is partially withdrawn (preferably while still being turned in the 
same direction) back into the guide bore 52 by a sufficient distance to 
clear the open area 50 of the sharpener body channel for the arrival of 
the next cutting link. The middle clamping screw 58 is then loosened, and 
the saw chain 20 is manually advanced (preferably by means of the 
protective hand slide of FIG. 11, as will be described hereinafter) to 
bring the next cutting link into the sharpening position adjacent to the 
opening of the guide bores 52. Since the next cutting link will be a 
left-hand cutting link 24 as shown in FIG. 1, manual advancing of the saw 
chain is continued until the next right-hand cutting link is moved into 
position. It should be noted that, due to the ability of the pawl member 
100 to pivot freely in the direction away from the end portion 41 of the 
upper web (i.e., in a counter-clockwise direction as viewed in FIG. 3), 
the pawl member does not obstruct the passage of the successive cutting 
links through the open area 50 of the sharpener body channel. When the 
next right-hand cutting link has moved past the pawl member 100 and into 
the open area 50 of the channel, it is then moved in the reverse direction 
until the rear portion of the cutting link abuts against the lower end of 
the pawl member 100. Since the pawl member 100 is restrained against 
movement in a direction toward the end portion 41 of the upper web (i.e., 
in the clockwise direction as viewed in FIG. 3) by the shelf 106, the pawl 
member will resist further movement of the cutting link in this direction. 
This places the next right-hand cutting link in the same position occupied 
by the right-hand cutting link that was previously sharpened, whereby the 
next right-hand cutting link is now properly located relative to the guide 
bore 52 for sharpening. The middle clamping screw 58 is then retightened 
to clamp the cutting link in place. The sharpening operation is then 
repeated by inserting the rotary burr 86 and rotating the hand crank 92 
until the abradant end portion 88 of the burr extends fully into the open 
area 50 of the sharpener body channel as shown in FIG. 6. The rotary burr 
is the partially withdrawn, as before, and the middle clamping screw 58 is 
loosened so that the saw chain 20 may again be advanced to bring the next 
right-hand cutting link into position for sharpening. 
The foregoing sequence of operations is repeated until all right-hand 
cutting links on the saw chain 20 have been sharpened. As this point, the 
clamping screws 58 and 108 are loosened, the pawl member 100 is withdrawn 
fully toward the edge of the end portion 41 of the upper web, and the saw 
chain 20 is advanced to bring a left-hand cutting link within the open 
area 50 of the sharpener body channel adjacent to the guide bore 54. The 
alignment pin 116 is then inserted fully into the second guide bore 54 and 
its projection 126 is engaged with the notch 55 on the sharpener body. The 
left-hand cutting link 24 is then advanced until its cutting edge 28 is 
brought into contact with the reduced end portion 120 of the alignment 
pin, whereupon the middle clamp screw 58 is tightened to clamp the 
left-hand cutting link in position. The U-shaped support member 102 is 
then moved forward to bring the lower end of the pawl member 100 into 
contact with the rear edge of the cutting link 24, and the clamping screw 
108 is tightened to lock the U-shaped member 102 and pawl member 100 in 
position. The middle clamping screw 58 is then loosened and the alignment 
pin 116 is removed from the guide bore 54. With the rear edge of the 
left-hand cutting link 24 resting against the pawl member 100, the middle 
clamping screw 58 is retightened in preparation for sharpening. Sharpening 
is now carried out by inserting the rotary burr 86 into the guide bore 54, 
rotating the hand crank 92 until the base of the hand crank is brought 
into contact with the flattened corner 51 of the sharpener body, and then 
partially withdrawing the rotary burr from the guide bore 54 (preferably 
while still turning the hand crank 92). The middle clamping screw 58 is 
then loosened to permit the next left-hand cutting link to be brought into 
position by manually advancing the saw chain 20. As described earlier, the 
ability of the pawl member 100 to pivot in a direction away from the end 
portion 41 of the upper web allows the successive cutting links to move 
freely through the open area 50 of the sharpener body channel in the 
forward direction between sharpening operations. After the next left-hand 
cutting link passes the pawl member 100, it is then moved in the reverse 
direction until the rear portion of the cutting link touches the pawl 
member 100. Since the pawl member 100 is restrained against movement in 
the reverse direction, it will resist further movement of the cutting link 
in this direction and will thereby serve to locate the next left-hand 
cutting link in the same position occupied by the first left-hand cutting 
link during the previous sharpening operation. The middle clamping screw 
is then retightened to clamp the next left-hand cutting link in position, 
and the sharpening operation is repeated by advancing the rotary burr 86 
into the open area 50 of the sharpener body channel while turning the hand 
crank 92. The foregoing sequence of operations is then repeated for the 
subsequent left-hand cutting links, until all left-hand cutting links on 
the saw chain 20 have been sharpened. 
In order to facilitate the sharpening operation, the first right-hand or 
left-hand cutting link to be sharpened may be provided with a visible mark 
(e.g., using crayon, nail polish, or any other suitable marking material) 
so that it may be easily identified when it again reaches the open area 50 
of the sharpener body channel. 
When the sharpening operation is completed, the right-hand and left-hand 
cutting links are visually inspected to assure that they are of the same 
length. If one set is found to be longer than the other, the sharpening 
operation is repeated on the longer set until uniformity is achieved. The 
clamping screws 58, 82 and 84 are then loosened and the sharpener body 38 
as a whole is removed from the saw bar 85. 
It will be appreciated that, by virtue of the alignment pin 116, it is 
possible to adjust the positions of the right-hand or left-hand cutting 
links within the sharpener body channel in a single operation, without the 
need for subsequent fine adjustments. The use of the alignment pin 116 is 
required only twice, once for the adjustment of the right-hand cutting 
link positions, and once for the adjustment of the left-hand cutting link 
positions. The positions of all subsequent right-hand cutting links (or 
all subsequent left-hand cutting links) are then established by the 
pivoting pawl member 100. It should also be noted that, due to the use of 
the alignment pin 116 for the necessary adjustment procedure, the 
possibility of damage to the abradant end portion 88 of the rotary burr 86 
is avoided. In the event that a cutting link is positioned too close to 
the selected guide bore 52 or 54 prior to the adjustment, it is the 
alignment pin (rather than the rotary burr) that will strike the 
improperly positioned cutting link. 
The construction of the sharpening kit can be simplified, if desired, by 
omitting the pawl member 100, U-shaped support member 102, and clamping 
screw 108. In that event, however, the alignment pin 116 must be employed 
repeatedly to position each successive right-hand or left-hand cutting 
link in the proper location for sharpening. This, in turn, requires 
repeated removal and reinsertion of the rotary burr 86. Hence it is 
preferred that the pawl member 100, U-shaped support member 102, and 
clamping screw 108 be retained for use in positioning the successive 
cutting links in the manner described previously. 
It should be pointed out that the alignment pin 116 may be provided with a 
configuration different from that illustrated in FIGS. 7 and 8. Thus, for 
example, the reduced end portion 120 of the alignment pin may be made 
concentric or coaxial with the shank portion 118, if desired, and the 
diameter of the reduced end portion 120 may then be made less than that of 
the widest part 87 of the abradant end portion 88 of the rotary burr 86. 
The difference in radius between the reduced end portion 120 of the 
alignment pin and the widest part 87 of the abradant end portion 88 of the 
rotary burr will then determine the amount of stock removal from the 
cutting edges 28 of the cutting links 22, 24 during the sharpening 
operation. In this embodiment, the rotational position of the alignment 
pin in the guide bores 52, 54 would not be important and the projection 
126 on the alignment pin could therefore be eliminated. However, the 
embodiment illustrated in FIGS. 7 and 8, wherein the reduced end portion 
120 of the alignment pin is eccentrically offset from the shank portion 
118 and is equal in diameter to the widest part 87 of the abradant end 
portion 88 of the rotary burr, is preferred for the reason that it allows 
the circular curvature of the reduced end portion 120 of the alignment pin 
to be matched precisely to the circular curvature of the cutting edges 28 
of the right-hand and left-hand cutting links 22 and 24. This permits the 
cutting edges of the cutting links to be smoothly and positively engaged 
with reduced end portion 120 of the alignment pin 116 during the 
adjustment procedure. 
FIG. 9 is an exploded perspective view of a depth gauge attachment 130 
which permits the sharpening kit of FIGS. 2-6 to be used alterntatively to 
file the depth gauges 30 of the saw chain 20 in FIG. 1. This will normally 
be done after the cutting edges 28 of the left-hand and right-hand cutting 
links 22, 24 on the saw chain 20 have been sharpened as described 
previously. The depth gauge attachment 130 includes an elongated gauge bar 
132 which is shaped and dimensioned to be received in the upper part of 
the channel 46 of the sharpener body 38, along the underside of the upper 
web 40, 41, and a threaded fastener 134 with an enlarged head portion 136. 
The threaded shaft 144 of the fastener 134 is dimensioned to be loosely 
received through the threaded bore 110 in the upper web portion 41 of the 
sharpener body 38, and is engageable with a threaded bore 133 which 
penetrates the gauge bar 132. The threaded bore 133 is located closer to 
one end of the gauge bar 132 than to the other end thereof, as shown in 
FIG. 9. As shown more clearly in the end view of FIG. 10, the gauge bar 
132 has a flat surface 138 on the underside thereof, and the two upper 
longitudinal edges 140, 142 of the gauge bar are rounded or beveled as 
shown. The two interior edges 57, 59 of the sharpener body channel 46 in 
FIG. 1 are rounded in a manner complementing the beveled edges 140, 142 of 
the gauge bar 132. 
Referring now to FIG. 13, the depth gauge attachment is affixed to the 
sharpener body by first removing the clamping screw 108 and the U-shaped 
member 102 which supports the pawl 100, placing the gauge bar 132 in the 
upper part of the channel 46 of the sharpener body so that the beveled 
edges 140, 142 of the gauge bar rest smoothly along the rounded interior 
edges 57, 59 of the channel, and then inserting the threaded fastener 134 
through the bore 110 and into engagement with the threaded bore 133 in the 
gauge bar 132. When the threaded fastener 134 is tightened, the enlarged 
head portion 136 thereof bears against the top surface of the upper web 
portion 41, thereby bringing the gauge bar 132 into abutting contact with 
the underside of the upper web. The engagement between the upper beveled 
edges 140, 142 of the gauge bar 132 and the rounded interior edges 57, 59 
of the sharpener body channel 46 assures a smooth mechanical fit between 
the two. A narrow ledge 43 is preferably provided in the sharpener body 
channel 46 along the inside of the second side wall 44, assist in locating 
the gauge bar 132. In use, the flat underside surface 138 of the gauge bar 
132 provides a guide surface for the upper portions of the cutting links 
22, 24 on the saw chain 20 of FIG. 1. The thickness of the gauge bar 132 
is selected to cause the saw chain 20 to assume a sufficiently lower 
position within the channel 46 of the sharpener body 38 to bring the top 
of the depth gauge portions 30 into contact with the abradant end portion 
88 of the rotary burr 86 when the rotary burr is inserted into one of the 
guide bores 52, 54. In the illustrated embodiment, the depth gauge filing 
operation is carried out by inserting the rotary burr 86 into the guide 
bore 54, although it will be apparent that the assembly could be modified, 
if desired, to use the guide bore 52 for this purpose. 
The depth gauge attachment 130 is preferably used in conjunction with a 
protective hand slide 144, which is shown in perspective in FIG. 11. The 
hand slide 144 comprises an elongated handle member 146 which is adapted 
to be placed against the bar 85 of the chain saw, the handle member having 
a longitudinal channel 148 therein for receiving the saw chain 20. A pin 
150 is mounted transversely in the central portion of the channel 148 for 
engaging a cutting link of the saw chain. The handle member 146 is 
provided with enlarged portions 152, 154 at each end thereof on the side 
opposite the channel 148 to prevent the user's hand from inadvertently 
slipping off the handle member 146. In use, the hand slide 144 is placed 
against the bar 85 of the chain saw on the side opposite to that on which 
the sharpener body 38 is mounted, as shown in FIG. 13, and the pin 150 is 
engaged with a cutting link 22 or 24, or between two successive cutting 
links. The hand slide 144 may then be used to advance the saw chain 20 
around the saw bar 85 without the risk of injury from the sharpened 
cutting edges of the cutting links. This greatly facilitates the depth 
gauge filing operation, which requires that the cutting links 22, 24 be in 
motion while the rotary burr 86 is turned. It should be noted that, 
although FIG. 13 shows the hand slide 144 in engagement with the lower 
portion of the saw bar 85, the hand slide 144 is not self-supporting 
thereon and must be maintained in contact with the saw chain 20 by the 
pressure of the user's hand. 
It will be apparent that the pin 150 of the hand slide 144 may be replaced, 
if desired, by any other means suitable for engaging the saw chain 20. 
Thus, for example, the channel 148 of the hand slide may be formed with an 
integral transverse rib or projection in the central part thereof, in lieu 
of the pin 150. 
The use of the depth gauge attachment 130 of FIGS. 9-10 will now be 
described with reference to FIGS. 12-13. As noted earlier, the clamping 
screw 108 and the U-shaped support member 102 for the pawl member 100 are 
removed prior to the installation of the depth gauge attachment 130, since 
these components are not required during the depth gauge filing operation. 
The gauge bar 132 is now inserted into the sharpener body channel 46 with 
its beveled edges 140, 142 engaging the rounded interior edges 57, 59 of 
the sharpener body channel, and with an equal amount of the gauge bar 132 
protruding from each end of the channel 46. The sharpener body is then 
placed over the saw bar 85 so that the gauge bar 132 rests in a flat 
position atop the saw chain 20, as shown in FIG. 12. The two outer 
clamping screws 82, 84 are then tightened to clamp the sharpener body 38 
to the saw bar 85. With the sharpener body now properly seated atop the 
saw chain 20, the gauge bar is withdrawn to the extent necessary to align 
the threaded bore 133 therein with the larger threaded bore 110 in the 
upper web portion 41 of the sharpener body. The threaded fastener 134 is 
then inserted through the bore 110 so that it engages the threaded bore 
133 in the gauge bar 132, whereupon the fastener 134 is tightened to draw 
the end of the gauge bar 132 upward into snug engagement with the 
underside of the upper web portion 41 within the sharpener body channel 
46. The components are now in the relationship illustrated in FIG. 13. It 
will be observed that the left-hand portion of the gauge bar 132 protrudes 
beyond the left-hand end of the sharpener body channel 46, whereby this 
portion of the guage bar 132 now serves as a guide for the saw chain 20 
outside the sharpener body 38. It will also be observed that the 
right-hand end of the gauge bar 132 is positioned to the left of the 
opening of the guide bore 54, thereby providing the necessary clearance 
for the insertion of the abradant end portion 88 of the rotary burr 86. 
Thus, in its full use position as illustrated in FIG. 13, the gauge bar 
132 occupies only a portion of the length of the sharpener body channel 
46, this portion not including the area immediately adjacent to the 
opening formed by the guide bore 54 in the second side wall 44 of the 
sharpener body. 
With the foregoing set-up procedure now completed, the depth gauge filing 
operation may be carried out in connection with the rotary burr 86. It 
should be noted that the rotary burr 86 is preferably the same as that 
which was used during the sharpening operation; therefore, the only 
additional components required for the depth gauge filing operation are 
the depth gauge attachment 130 and (optionally) the protective hand slide 
144. The depth gauge filing operation is commenced by fully inserting the 
abradant end portion 88 of the rotary burr 86 into the guide bore 54, and 
pressing the protective hand slide 144 into engagement with the saw chain 
20 on the underside of the saw bar 85. The hand slide 144 is then used to 
advance the saw chain 20 in the left-hand direction through the sharpener 
body 38 to a point where the cutting edge of the cutting link is not 
touching the abradant end portion 88 of the burr. The hand crank 92 is 
then turned in the direction indicated in FIG. 13 while the saw chain 20 
is advanced, using the protective hand slide 144, in the left-hand 
direction through the sharpener body 38. This motion is opposite to the 
direction in which the saw chain 20 normally travels when the chain saw is 
in operation. As the depth gauge portion 30 of the cutting link passes 
under the burr, it is filed to the proper height as determined by the 
thickness of the gauge bar 132 and the diameter of the widest part 87 of 
the abradant end portion 88 of the burr. The turning of the hand crank 92 
is continued until the depth gauge 30 has been completely filed, whereupon 
the rotary burr 86 is partially retracted into the guide bore 54 to allow 
the next cutting link to be brought into position. The foregoing sequence 
of operations is then repeated to file the depth gauge portion 30 of the 
remaining cutting link. It should be noted it is not necessary to 
discriminate between the right-hand and left-hand cutting links 22 and 24 
during the depth gauge filing operation. Thus the cutting links of both 
types may be filed sequentially while the rotary burr 86 remains within 
the guide bore 54. It should also be noted that, since the cutting links 
are required to be in motion during the depth gauge filing operation, the 
middle clamping screw 58 is not tightened and the clamping strip 60 is 
thereby kept disengaged from the sides of the cutting links 22, 24. 
At the conclusion of the depth gauge filng operation, the rotary burr 86 is 
removed and the outer clamping screws 82 and 84 are loosened to allow the 
sharpener body 38 to be removed from the saw bar 85. The threaded fastener 
134 is then removed and the gauge bar 132 is withdrawn from the sharpener 
body channel. The U-shaped member 102 and clamping screw 108 may then be 
replaced as shown in FIGS. 2-6 to prepare the sharpener for a later 
sharpening operation. Preferably, the rotary burr 86 is reinserted into 
one of the guide bores 52, 54 for storage in order to protect the abradant 
end portion 88 of the burr from possible damage. 
In practice, it will usually be necessary to file the depth gauges every 
fourth or fifth time that the cutting edges of the cutting links are 
sharpened, or whenever a large amount of material is removed from the 
cutting edges as a result of sharpening. 
It will be appreciated that, by providing for the alternative attachment of 
the U-shaped support member 102 and pawl member 100 (which are required 
only during the sharpening operation), or the depth gauge attachment 130 
of FIGS. 9-10, it is only necessary to manufacture one type of sharpener 
body 38 which can then be adapted to both purposes. A further advantage of 
this arrangement is that the basic sharpening kit of FIGS. 2-6 can be sold 
with or without the depth gauge attachment of FIGS. 9-10, but the 
purchaser of the basic sharpening kit has the option of later puchasing 
the depth gauge attachment separately for use in connection with the 
originally-purchased sharpener. 
Although the protective hand slide 144 of FIG. 11 is primarily intended for 
use in connection with the depth gauge attachment 130 of FIGS. 9-10, the 
hand slide 144 can also be used during the sharpening operation described 
earlier in connection with FIGS. 2-6. Such use of the protective hand 
slide 144 is illustrated in FIG. 14. After a given cutting link has been 
sharpened, and the middle clamping screw 58 has been loosened to release 
the clamping pressure on the sharpened cutting link, the hand slide can be 
pressed against the saw chain 20 on the opposite side of the saw bar 85, 
as shown, in order to advance the next cutting link into position for 
sharpening. 
Although the details of construction of the chain saw kit are not necessary 
to an understanding of the invention, a preferred manner of construction 
will be described briefly for the purpose of illustration. The sharpener 
body 38 in FIG. 2 is preferably made from a high-strength material, such 
as die-cast zinc alloy. The same material may be used for the gauge bar 
132 of the depth gauge attachment 130. The sharpener body 38 may be cast 
in two parts, the first part comprising the first side wall 42, the upper 
web 40, 41, and the upper half of the horizontal extention 48, and the 
second part comprising the second side wall 44 and the lower half of the 
horizontal extension 48. The seam between these two parts is indicated at 
61 in FIGS. 2, 4, and 5. These two parts may be joined by a number of 
studs, rivets or other suitable fasteners (not shown) penetrating the 
upper and lower halves of the horizontal extension 48 on either side of 
the guide bores 52, 54. Pairs of integral strengthening ribs 63 and 65 
(also visible in FIGS. 2, 4 and 5) are preferably provided above and below 
the horizontal extension 48 where it adjoins the second side wall 44 in 
order to provide added structural support. The pawl member 100 is 
preferably made from a hardened sintered metal, which nearly matches the 
cutting links of the saw chain 20 in hardness. This prevents undue wear on 
the pawl member 100 due to repeated contact with the cutting links of the 
saw chain. Tempered steel liner bushings 67, 69 are preferably provided in 
the guide bores 52, 54, as shown in FIG. 6, in order to provide a smooth 
and accurate fit for rotary burr 86. As noted earlier, the rotary burr 86 
is preferably machined from tungsten carbide, or some other material of 
suitable hardness and durability, to provide a sharpening surface which 
will not readily become worn after repeated uses. The hand crank 92 and 
swivel-type handle 98 which are attached to the rotary burr 86 are 
preferably made from the same zinc alloy material that is used for the 
sharpener body 38. The same material may also be used for the U-shaped 
pawl supporting member 102. Steel is a suitable material for the alignment 
pin 116; in this case, wear is not a serious problem since the alignment 
pin is used only briefly during the sharpening operation. The protective 
hand slide 144 may be made from aluminum, if desired, or from the same 
zinc alloy material that is used for the sharpener body 38. The various 
clamping screws and fasteners 58, 82, 84 and 108, as well as the swivel 
pin 94, may be made from zinc-plated steel or the like. The flexible 
clamping strip 60 is preferably made from spring-tempered steel as noted 
earlier. The screw 74, lock washer 76, set screw 91, and pins 104 and 150 
are standard hardware items and may be made from any suitable material. 
It will ordinarily be desirable to manufacture the rotary burr 86 in a 
number of different sizes so that the sharpening kit of the present 
invention can be used with all of the commonly-used saw chain sizes. 
Exemplary dimensions for the widest diameter portion 87 of the abradant 
end portion of the rotary burr (before machining) are 5/32 inch, 3/16 
inch, and 7/32 inch. For the 5/32-inch burr, the length of the tapered 
portion 89 will be about 0.324 inch, the length of the maximum-diameter 
portion 87 will be about 0.541 inch, and the burr diameter at the tapered 
tip will be about 1/16 inch. For the 3/16-inch burr, these dimensions will 
be about 0.336 inch, 0.559 inch, and 5/64 inch, respectively. For the 
7/32-inch burr, these dimensions will be about 0.367 inch, 0.568 inch, and 
3/32 inch, respectively. For all burr sizes, the diameter of the shank 
portion 90 is about 0.250 inch and the burr is about 2.75 inches in 
overall length. The alignment pin 116 has a head portion 122 which is 
about 1/2 inch in diameter and a shank portion 118 which is about 0.250 
inch in diameter, with the projection 126 extending out from the underside 
of the head portion 122 by about 1/16 inch. The diameter of the reduced 
end portion 120 of the alignment pin 116 will depend upon the burr size 
used, and in each case should be substantially equal to the diameter of 
the widest part 87 of the abradant end portion 88 of the burr. Thus, for 
the 5/32-inch, 3/16-inch, and 7/32-inch burr sizes, the diameter of the 
reduced end portion 120 of the alignment pin 116 will be about 0.156 inch, 
0.187 inch, and 0.218 inch, respectively. In each case, the axis of the 
reduced end portion 120 of the alignment pin is displaced from the axis of 
the shank portion 118 by about 0.015 inch in the horizontal direction and 
by about 0.004 inch in the vertical direction, taking the horizontal and 
vertical directions to be defined as shown in FIG. 8 (i.e., with the 
projection 126 pointing vertically upward). The overall length of the 
alignment pin will of course depend on the size of the sharpener body 38 
(as will the length of the rotary burr 86), but in the preferred 
embodiment the total length of the shank portion 118 and the reduced end 
portion 120 is about 2 inches, with the shank portion 118 being about 13/8 
inches in length and the reduced end portion being about 5/8 inch in 
length. The sharpener body 38 is preferably about 31/4 inches long 
(measured along the side walls 42 and 44), 13/4 inches high, and 21/8 
inches deep (including the horizontal extension 48). The side walls 42, 44 
and upper web 40, 41 of the sharpener body are preferably about 3/8 inch 
thick. The horizontal extension is preferably about 1/2 in thickness, 
2-3/16 inches in length, and extends outwardly from the second side wall 
44 of the sharpener body by about 1 inch. The sharpener body channel 46 
preferably has a width of about 3/8 inch between the side walls 42 and 44, 
with a vertical distance of about 5/32 inch being provided between the top 
inside surface of the channel 46 and the plane which contains axes of the 
two horizontal guide bores 52 and 54. The thickness of the gauge bar 132 
of FIGS. 9-10 should then be about 0.209 inch (for the 5/32-inch burr), 
0.222 inch (for the 3/16-inch burr), or 0.235 inch (for the 7/32-inch 
burr). The overall length of the gauge bar 132 is preferably about 4 
inches. The hand slide 144 of FIG. 11 is about 41/2 inches in length, and 
the longitudinal channel 148 therein is about 3/8 inch in width and 0.312 
inch in depth. The pin 150 may comprise a standard 1/8-inch diameter roll 
pin which is press-fitted into suitable holes formed in the sides of the 
hand slide 132. A clearance of about 0.0075 inch is preferably maintained 
between the periphery of the pin 150 and the bottom surface of the channel 
148 to prevent the pin 50 from making contact with the sharpened cutting 
edges 28 of the cutting links on the saw chain 20 of FIG. 1. 
It is to be understood that all of the foregoing dimensions and material 
specifications are presented merely by way of example and are not intended 
to limit the scope of the invention in any way. 
Although the present invention has been described with reference to a 
preferred embodiment, it is to be understood that the invention is not 
limited to the details thereof. A number of possible modifications and 
substitutions have been suggested in the course of the foregoing detailed 
description, and others will occur to those of ordinary skill in the art. 
All such modifications and substitutions are intended to fall within scope 
of the invention as defined in the appended claims.