Shaft tapering device

A shaft tapering device having a body block with a transverse borehole through which the shaft to be tapered is introduced. A recess in the top of the body block intersects the borehole, forming an aperture into which a cutting blade extends substantially tangential to the curvature of the borehole. A cradle attached to the body block includes a pair of parallel wing-like members spaced apart by spreaders at each end of the wings, which are pivotably mounted to the body block. Each wing has a notch formed in the upper edge thereof that is semicircular in the deepest part and on pivoting the wings the deepest part of the notches can be substantially aligned with the borehole. On holding a handle attached to the body block, pivoting the wings during rotation of a workpiece, and moving the device laterally, the work piece is quickly and controllably tapered, the notches in the wings of the cradle bringing the work piece to the cutting blade with the work piece substantially centered under the cutting edge at all times. A portable kit combines the tapering device with a guide frame having a longitudinal way joining a head stock with a tail stock, and with a tapering template extending between the two. A template follower attached to the forward spreader of the cradle rides on the template and automatically pivots the cradle as the device is slid along the way as the work piece is rotated by a drill motor mounted on the head stock.

FIELD OF THE INVENTION 
The invention relates to a device useful for making a shaft or rod of 
any-material that can be turned on a lathe, such as, wood or polymeric 
material or metal, whether of uniform diameter, or of uniform taper, or of 
controllably random taper, to a method of tapering and to apparatus for 
conveniently controlling the taper. 
BACKGROUND OF THE INVENTION 
A number of devices and apparatuses have been patented that may be used to 
make dowels and shafts of various types, including tapered shafts, usually 
from wooden work stock. There are also devices for shaving, e.g., dowels, 
to custom fit them. These ordinarily require the use of a lathe for 
rotating the work piece, and usually make use of a rigid frame called a 
longitudinal way or bed with a driving head with a driven chuck at one end 
and an idler tail head or tail stock at the other end. Usually, there is 
also provided a tool rest that mounts on the way or bed and is movable 
along the way or bed. As an example, there is the apparatus of Johnson, 
U.S. Pat. No. 3,771,392, who describes a tool rest and tool holder, but 
not means for quickly and conveniently moving the tool holder along the 
longitudinal way, and especially not in a reproducible manner from work 
piece to work piece. 
None of the patented devices, so far as is known presently, provides 
adequate means for easily and accurately controlling the taper of the work 
piece, especially of a shaft longer than several inches, and also lacking 
is means for conveniently keeping the work piece centered under the 
leading edge of the cutting blade at all times while being worked. The 
device of Lippolt, U.S. Pat. No. 4,497,352, appears to make some provision 
for approximate centering of the work piece as it is forced into the 
unsymmetrical V-shaped groove of the stationary block, but the provisions 
for tapering are not very convenient to carry out in practice, and not 
quickly done. 
The patents to Hilton, U.S. Pat. No. 3,229,731; Sprague, U.S. Pat. No. 
2,913,019; Zemrowski, U.S. Pat. No. 2,848,020; and Durgin, U.S. Pat. No. 
232,634; each describe devices for turning shafts in which a support bar 
or a second blade serves as a spacer defining the diameter of the shaft 
obtained, with adjustment means. But the adjustment means are not easily 
adjusted so that is it neither easy nor convenient to make a tapered 
shaft, and certainly not quickly. 
Other turning tools are described by Gifford, U.S. Pat. No. 68,064 and 
Webber, U.S. Pat. No. 14,173. 
There is also a need to provide apparatus for making tapered shafts up to 
at least three inches or more in diameter that is not only convenient to 
use, but modest in cost, and, portable if desired, especially for the 
making of shafts of wood or other light turnable material up to at least 
an inch in diameter and up to about six feet in length or longer, and 
also, to make all such shafts reproducibly, if desired. 
SUMMARY OF THE INVENTION 
In a first aspect the invention is a shaft tapering device made up of a 
body block, usually a substantially rectangular solid, with a transverse 
borehole and an aperture from the top side intercepting the borehole and 
having provisions for mounting a cutting blade to extend slightly and 
operatively into the borehole; a guiding cradle longer than the body block 
and having arms pivotably mounted, one arm on each lateral side of the 
body block, for guiding the work piece; and a handle rigidly attached to 
the rear portion of the body block for manual or other control thereof. 
The arms of the guiding cradle are joined at their respective ends by 
spacers or spreaders and are pivotably attached at about their mid-length 
to the lateral sides of the body block. Each arm is provided with guide 
means in the form of a J-shaped notch or equivalent-acting structure such 
as a loop of heavy gauge wire, for supportively guiding the work piece 
being worked on to the cutting blade. 
Each guide means, i.e., each notch or equivalent structure, is shaped 
semicircularly in the deepest part, and on pivoting the guiding cradle, 
e.g., from a horizontal position, downwardly with respect to the front 
side of the body block, the semicircular deepest parts are alignable with 
the borehole of the body block and are usually selected to be of the same 
or similar diameter and must be large enough to accommodate the initial 
size of the work piece. 
When the semicircular deepest part of each J-shaped notch or equivalent is 
aligned with the adjacent borehole the notch may be seen to be positioned 
at an angle to the top side of the body block with the edge defining the 
back side of the notch corresponding to the long leg of the "J" at an 
angle of about 40 to 45 degrees to the top side of the body block, and 
especially to a line drawn between the top of the borehole and the point 
about which the arms pivot. 
The front defining edge of each J-shaped notch or equivalent structure, 
i.e., the edge facing in the direction of the handle of the device, is 
about tangential with the semicircular part, flaring away somewhat from 
the tangential line and extending up with very slight curvature to reach 
the top side of the body block at an angle of about 83 to about 88 
degrees. 
The pivotal arms each pivot about a point on the body block between the 
borehole and the rear side of the body block, and about at the level of 
the top of the borehole, and spaced from the nearest edge of the borehole 
a distance about equal to the diameter of the borehole. 
When the device is appropriately assembled, a work piece being rotated and 
tapered by the cutting blade as the cradle is tipped upwardly with respect 
to the front of the body block, e.g., by hand pressure being placed on the 
rear spreader if done manually, will be guided or advanced towards the 
cutting blade with the center of rotation of the work piece being 
consistently just under about the leading edge of the cutting blade. With 
no work piece in the device, when the front of the cradle is tilted 
upwardly so that the deepest part of the notch passes across the borehole, 
as the deepest part is not quite past the borehole, the remaining clear 
"sight" or passage visible through the borehole will be looking 
substantially right across the leading edge of the cutting blade. 
Preferably the arms of the guiding cradle take the form of wings cut from 
metal plate that may be generally rectangular in shape but are more 
preferably each rounded convexly along the bottom edge like a rocker of a 
rocking chair, and about straight across the upper edge except for the 
notch. Most preferably, the rear portions are somewhat upswept to avoid 
having the rear Spreader come down awkwardly close to the handle when the 
front of the cradle is tipped upwardly during tapering operations, though 
the handle may also be attached to extend downwardly from the rear of the 
body block. 
In another embodiment of the present device, the bottom side of the body 
block is provided with an aperture communicating with a portion of the 
bottom of the borehole, generally the width of the cutting blade, for the 
ready discharge of shavings or turnings, the aperture also reducing the 
weight of the body block. 
While the cradle may be pivoted manually in use without a guide, it is 
highly convenient to employ with the present tapering device a novel 
tapering guide having a longitudinal way joining a head stock and a tail 
stock which support a tapering template member and, usually, to 
incorporate in the guide apparatus the drive means for rotating the work 
piece. Such a tapering guide consists of an elongated frame, generally 
rectangular, and readily made of wood, structural plastic or light metal, 
that joins the head stock and the tail stock which in turn support the 
tapering template member at a longitudinal tilt. The template member 
serves as a guide for the pivoting of the cradle in order to get the taper 
sought to be obtained. A template follower, usually in the form of a 
simple rod or bar, is rigidly attached extending forwardly from the 
spreader at the distal end of the cradle. The spreader must not be 
rotatable in its mount. 
The frame includes a way or bed for the present novel tapering device to 
ride upon with the spacing from the tapering template member being such 
that the follower rod is readily held manually or mechanically against the 
upper surface of the template rod as the tapering device is slid along the 
way while the work piece is rotated and turned to size in the tapering 
operation. 
Usually the frame includes means at one end thereof for mounting power 
means for holding and rotating the work piece. In many cases the power 
means may be a conventional one-quarter inch or three-eighths inch drill 
motor which is simply, and often releasably, clamped to the frame with the 
chuck extending through an aperture in the head stock. 
The frame of the tapering guide consists of the head stock and a tail stock 
connected by at least one elongated spacing member that slides adjustably 
through or past the head stock and tail stock. A support for the motor 
used as rotational power means is provided on the outer face of the head 
stock and positioned so that the chuck will extend easily through an 
aperture in the head stock and be accessible for mounting a work piece. A 
corresponding aperture is provided in the tail stock for the work piece to 
extend through to limit any gyrations thereof. At the back edges of the 
head stock and tail stock are provided also means for clamping the 
respective ends of the template rod employed. In the case uniform taper is 
desired, the tapering template member is simply a straight rod positioned 
to incline or tilt upwardly to the requisite extent needed to pivot the 
cradle to get the amount of taper desired. Preferably a straight edged 
member is positioned between the head stock and the tail stock at about 
the bottom edges thereof to serve as a convenient support for the present 
shaft tapering device as it is moved along the work piece during tapering 
operations. 
The shaft tapering device and the tapering guide together constitute a 
convenient, useful kit that is readily made to be portable for most 
operations.

DETAILED DESCRIPTION OF THE INVENTION 
As used herein, "upwardly" means in a generally vertical direction, and 
with respect to the novel device, movement of the front end of the cradle 
and its wings "upwardly" refers to the direction the movement of the front 
end of the cradle would take with respect to the front side of the body 
block when it is operatively employed in tapering a work piece. 
The term "remaining centered" means, with respect to the work piece in the 
borehole during tapering operations, that the work piece remains at 
substantially all times as its radius is reduced with its center of 
rotation just below the leading edge of the cutting blade. 
Turning now to the drawings in which like parts are referred to by like 
reference numerals, and particularly to FIGS. 1 to 5, the shaft tapering 
device of the invention is seen to be identified generally by the 
reference numeral 10. Tapering of a work piece takes place inside the body 
block 11, inside the borehole 12 that extends transversely between the 
lateral sides 13. The shaving or cutting is done by a cutting blade 14 
positioned in a rather shallow inclined recess 15 in the upper side 16 of 
the body block 11, the recess 15 inclining downwardly in the direction 
from the rear to the front of the body block and intersecting the borehole 
12 to form an aperture 17 through which the cutting blade 14 extends. The 
incline angle of the floor of the recess 15 should hold the cutting blade 
14 appropriately for the cutting attack on the work piece, as well 
understood in the art, generally along a line tangential to the surface of 
the work piece as it is rotated. If the work piece is being turned to a 
uniform diameter the cutting blade will usually have 90 degree corners at 
the cutting edge, while a cutting blade for tapering should have rounded 
corners, such as blade 14 seen in FIG. 5. The cutting blade 14 is secured 
to the floor of the recess, for example, with a screw such as screw 18. 
The recess 15 extends nearly from side to side of the body block, or at 
least sufficiently wide to accommodate a typical cutting blade. 
Mounted pivotally to the lateral sides 13 of the body block 11 is a cradle 
indicated generally by the numeral 19. The cradle 19 is made up of two 
substantially identical rocker-like members or wings 20 that are held 
spaced apart by spacer elements or spreaders 21 adjacent the ends of the 
wings 20. Pivotal mounting of the cradle 19 is achieved by pivotably 
attaching the respective wings 20 to the respective lateral sides 13 of 
the body block 11 between the borehole 12 and the rear side 23 of the body 
block, where the handle 24 is attached. Preferably, the point of pivotal 
attachment is above the mid-height line of the body block and spaced about 
the diametric width of the borehole 12 from the nearest edge of the 
borehole to afford good action in positioning the work piece when the 
front end 25 of the cradle 19 is being pivoted upwardly to cause the work 
piece to be turned to a smaller diameter. 
The pivotal attachment may be made with screws 26 that extend through 
smooth bored holes 26a in the wings 20 into tapped holes 27 in the body 
block 11. To prevent "grabbing" by the heads of the screws 26 the wings 20 
may have a boss 28 formed around the openings of the bored holes 26a on 
the outer faces of the wings, or a washer 28a may simply be used. 
Similarly, a boss 29 may be formed on the inner face of each wing 20 
around the bored hole for the screw 26, or a washer 29a used to avoid 
friction between the wings 20 and the body block 11 during pivoting of the 
cradle 19. 
The spreaders 21, which hold the wings appropriately spaced apart, may each 
be a simple spacer element that is rod-like or rectangular in section, but 
with an axial borehole 30 so that a bolt 31 may be inserted therethrough 
and through boreholes 32 in the opposed end portions of respective wings 
20 and secured by a nut 33. 
The rearwardly portions 22 of the wings 20 may be upswept, if desired, to 
allow pivoting thereof downwardly with assurance the rear spreader 21 will 
not ordinarily strike the handle 24 or the hand holding the handle. 
The handle 24 may be firmly attached to the rear side 23 of the body block 
11 in most any suitable manner, for example, by a connecting bolt or 
threaded element 34 that engages a tapped hole in the body block 11, the 
other end being anchored within the handle in a tapped hole or by being 
cemented or glued into a longitudinal borehole in the forward part of the 
handle. 
In a critical aspect of the invention, the upper edge 35 of each wing 20 
has formed therein an unsymmetrical, J-shaped notch 36 somewhat adjacent 
the front end 25 of the cradle, i.e., in the forward portion 37 of each 
wing 20, the notches being substantially identically shaped and located. 
While the lower edge 38 of each wing is preferably convexly curved about 
like the rocker of a rocking chair to provide more width adjacent the 
notch 36, the upper edge 35 may define a more or less straight line except 
for the notch 36 and the upswept rearward portion 22. The deepest part 39 
of each notch 36 is substantially semicircular to readily support a work 
piece during shaving or turning. The diameter selected is usually about 
the same as that of the borehole 12, and that is usually dictated by the 
initial size of the work piece. The notches 36 are preferably formed about 
one-third to about one-fifth of the length of each wing 20 from the front 
end thereof, with the semicircular part of the notch 36 being at the 
requisite spacing from the pivot point of the wing, at the pivot screw 26, 
to be alignable with the borehole on pivoting the front end of the cradle 
downwardly. 
The front edge 40 of each notch extends away from the semicircular part 
along about a tangential line therefrom with the line meeting the upper 
edge 35 of the wing, in both cases, at an angle of a little less than 90 
degrees on the order of about 83 to about 88 degrees, slightly forming a 
hook. The opposing edge 41 of each notch, i.e., the edge inclined 
rearwardly, and being the long leg of the J-shape, diverges from being 
co-parallel with the front edge 40 and with very slight continuing 
curvature extends rearwardly towards the upper edge 35 of the wing and 
particularly towards a line from the pivot point to the top of the 
borehole, at an angle in the range of about 40 to about 45 degrees. On 
selecting the slopes of the front and back edges of the notches 
appropriately together with the spacing of the notches from the pivot 
point, it is found that on inserting a work piece in the borehole of the 
novel shaft tapering device equipped with a cutting blade and rotating the 
work piece with power means while tipping the front end of the cradle 
upwardly, the diameter of the work piece is reduced, and as it is reduced, 
the work piece is guided towards the cutting blade at all times. The front 
edges of the notches pull the work piece somewhat rearwardly and the 
inclined opposing rear edges allow the work piece to move somewhat 
rearwardly appropriately so that the work piece remains with its axial 
center of rotation just under the cutting edge of the cutting blade for 
best shaving and turning operations. 
The wings 20 need not have any special shape, such as that shown in FIGS. 
1, 2, 5 and 6, but may be simply more or less rectangular plates or even 
pivotal arms each holding sufficient of a plate section for the essential 
notch that guides the work piece during operations. An equivalent 
structural element to the notch in a plate or plate section may be a loop 
formed of heavy gauge wire and firmly mounted on the pivotal arm so that 
it cannot yield laterally. It is to be specifically understood that for 
the purposes of the description and claims that the term "notch" is meant 
to embrace such equivalent structures. 
To avoid having the rear spreader strike the handle when the front of the 
cradle is pivoted upwardly, the handle may be attached at a downward angle 
from the lower part of the rear side of the body block, thus keeping the 
handle out of the way. 
In another embodiment of the present device a modified body block is 
utilized, such as body block 11a as seen in FIGS. 3 and 4 in which a 
recess 61 nearly the width of the body block is formed in the bottom side 
62 thereof, deep enough to intercept the borehole 12a, thus forming an 
aperture 63 communicating with the borehole and providing a ready avenue 
of escape for the shavings and turnings produced during turning and/or 
tapering of a work piece. If desired, the recess may be made extensive 
enough and a shallow boss 64 provided having means for attaching and 
storing, out of the way, a spare cutting blade or a blade with a different 
cutting edge profile. 
Turning now to FIG. 6, a highly useful, novel tapering guide for use 
together with a modified form of the shaft tapering device 10a of the 
invention is shown in perspective view with power rotating means for the 
work piece also shown in the drawing. The tapering guide apparatus, 
indicated generally by the numeral 45 is seen to have a head stock 46 and 
a tail stock 47 connected by a longitudinal way 48 and connecting guide 
rod 49. At the back vertical edges 59, 59a of the head stock 46 and the 
tail stock 47, respectively, are clamps 50 for holding a tapering template 
member 51 on which rides a template follower rod 52 attached to the 
modified front spreader 21a, which must not be rotatable in its mounting. 
The tapering template member 51 shown is a rod of uniform diameter that is 
tipped or tilted vertically as held in the clamps 50. The handle 24a of 
the shaft tapering device 10a has been pierced and the connecting guide 
rod 49 inserted therethrough. A tool support 53 is shown adjustably 
attached to the longitudinal way 48 and the body block 11a of the shaft 
tapering device is manually slidable along the tool support 53 to achieve 
uniform tapering as the work piece, here identified by the numeral 54, is 
rotated. A drill motor 55 is shown supported adjacent the head stock 46 
with the chuck 56 of the drill motor extending through a generously wide 
aperture 57 in the head stock, and the work piece 54 mounted in the chuck 
56. The work piece 54 here shown extends through the borehole 12a of the 
body block 11a and the notches 36a of the wings 20a of the shaft tapering 
device 10a and, further, through an aperture 58 in the tail stock which 
serves as a guide to avoid any large oscillations of the work piece. The 
dimensions of the handle 24a, together with the shaft tapering device 10a 
and the spacing from the connecting guide rod 49 to the axial line of the 
chuck 56 and work piece 54 must be selected appropriately so that the work 
piece rotation is centered axially within the borehole 12a. 
on rotating the work piece 54 in the apparatus by means of the drive means, 
drill motor 55, as shown, and manually sliding the shaft tapering device 
10a from left to right along the tool support 53 with the template 
follower rod 52 riding on the tapering template member 51, the cradle 19a 
is pivoted upwards in a steady manner and the work piece 54 is uniformly 
tapered smaller and smaller from left to right. 
If it is desired to turn the work piece 54 into a shaft of uniform 
diameter, the template member 51 is simply supported horizontally by the 
clamps 50 with no tilting aspect, as shown in dotted outline in FIG. 6, 
and accordingly the cradle 19a is not pivoted upon sliding the shaft 
tapering device along the tool support 53, whereupon a shaft of uniform 
diameter is obtained. 
On the other hand, a variably tapered or shaped shaft may be produced, and 
reproducibly, upon using as the tapering template member 51 a rigid 
member, such as that shown in FIG. 7, shaped to provide a cam-like surface 
on which the template follower rod 52 rides to pivot the cradle 19a 
appropriately up and down as the shaft tapering device 10a is moved 
translationally along the tool support 53 to generate the shape of shaft 
desired. 
It should be understood that most any rotational power means may be used to 
rotate the work piece when using the present shaft tapering device if 
portability is not essential, such as a drill press, a lathe motor, or a 
foot treadle, and the work piece may be mounted in or held by a chuck or 
lathe or other known mounting device for rotating a work piece. The drill 
motor provides satisfactory power in many instances but is usually needed 
for portability. 
While a template follower rod 52 has been shown on the front spreader 21 in 
FIG. 5 and described, it should be understood that such a template 
follower rod can be added to the rear spreader and the tapering guide set 
up to position a tapering template that the template follower rod will 
ride on at the back of the shaft tapering device. Such a template follower 
rod, or similar structure, can also be added to the rear spreader and used 
as a handle to grasp easily instead of the spreader itself in manual 
operations. 
If desired, the pivotal guiding cradle may be cast of metal or formed of 
plastic, or carved from a single piece of wood, combining the arms and 
spreaders into a single unit. 
A unique feature of the present shaft tapering device is that there is very 
little moving or advancing of the device towards the work piece, the 
device moving the work piece towards the cutting blade within the 
borehole, rather than the usual contrary movement of a cutting blade 
towards the work piece.