Rotary disc cutter and method of making same

A rotary disc cutter for cutting workpieces, especially gears and the like. The rotary cutter comprises a plurality of cutting blades arranged about the periphery of a rotary disc cutting body with at least a portion of the blades being roughing blades comprising a tip and two sides with each side having first and second side portions. The first side portion along with the tip defining a cutting surface of the blades while the second side portion is relieved such that a clearance is formed between the second side portion and the surface of the workpiece. The clearance being of a dimension to allow the flow of coolant therethrough thereby improving the cooling of the cutting surface and enhancing the flow of chips away form the vicinity of the blades. The invention further includes a substantially reduced number of blade segments. Alternative blade tip configurations are also disclosed.

FIELD OF THE INVENTION 
The present invention is directed to rotary disc cutters, particularly 
rotary disc cutters utilized in the production of gears, and to a method 
of producing rotary disc cutters. 
BACKGROUND OF THE INVENTION 
Rotary disc cutters are devices for cutting workpieces, such as gears, very 
rapidly. The cutters are usually designed whereby a single revolution of 
the rotary disc cutter produces one tooth space on a gear blank. When the 
rotary cutter has made as many revolutions as the gear blank has tooth 
spaces, the gear is completed. 
The basic form of a rotary disc cutter is shown, for example, in U.S. Pat. 
No. 2,315,147 to Wildhaber. The cutter comprises a relatively large 
diameter cutter with a plurality of blades located about the periphery 
thereof. A gap is present between the last and first blades in order to 
permit indexing of the gear blank when the gap is abreast of the blank. 
In general, both roughing and finishing blades are present on a rotary 
cutter. U.S. Pat. No. 2,327,296 to Wildhaber shows roughing blades being 
of gradually increasing height, up to the desired depth of a tooth slot, 
to enable each successive blade to cut deeper into the gear blank as the 
cutter revolves. During rough cutting the rotary cutter and the gear blank 
are usually held in a fixed position, although for gears of increased 
width, it may be necessary for the rotary cutter to translate relative to 
the gear in order to remove sufficient stock along the tooth length. 
Roughing blades are somewhat narrower than finishing blades in order to 
leave a slight amount of stock on the tooth surfaces for removal by the 
finishing blades. Since both the rotary cutter and gear are usually held 
stationary during rough cutting, roughing blades produce a generally 
complimentary-shaped surface profile on the gear. For example, a concave 
circular arcuate profiled roughing blade would produce a convex circular 
arcuate profile on a tooth surface. 
Following roughing, the finishing blades form the final surface of the 
tooth. The finishing blades are usually of uniform height and, during 
finish cutting, the rotary cutter and the gear blank are translated 
relative to one another along the length of the gear tooth thus enabling 
the finishing blades to produce a finished surface across the entire 
length of the tooth surface. 
Many variations of rotary disc cutters are known in the art. For example, 
rotary disc cutters comprising only roughing blades are known. It follows 
then that an accompanying rotary cutter comprising finishing blades is 
necessary to produce a finished gear. The sides of a tooth slot may be 
finished by a single rotary cutter comprising two blade groups, as 
disclosed in U.S. Pat. No. 2,315,147, for sequentially finishing the sides 
of a tooth slot. After the first group finishes a first side surface, the 
gear is "set-over", that is, rotated a defined amount, and the second side 
surface is finished by the second group of blades on the rotary cutter. A 
gap between the two blade groups permits the set-over or position change 
of the gear. 
The side surfaces on both the roughing and finishing blades are generally 
of circular arcuate profile although other profile shapes, such as 
involute, are also known. Both roughing and finishing blades comprise an 
end or tip and two side surfaces. Usually in roughing blades, the profiles 
of the side surfaces are all circular arcs based on the same center of 
curvature with only the length of the blades increasing in the direction 
of cutter rotation. Finishing blades may also have a curvature based on 
the same center. Such finishing blades may be utilized in the production 
of spur and helical gears as discussed in the previously mentioned U.S. 
Pat. No. 2,327,296 to Wildhaber. 
However, it is also known to modify the profiles of successive blades of 
rotary cutters. For example, U.S. Pat. No. 2,315,147 discloses that, for 
bevel gears, successive finishing blades may vary in profile shape each 
according to the position at which it is to cut along the length of the 
tooth as relative translational movement between the cutter and gear takes 
place during the finishing operation. The successive finishing blades 
comprise a varying radii of curvature to provide variation in profile 
curvature from end to end of the gear tooth. The varying profile shape 
approach may also be applied to the roughing blades. 
Profiles of finishing blades may have the same radius of curvature but the 
centers of curvature may be spaced either uniformly or nonuniformly along 
a line parallel to the tangent of the tooth profile according to U.S. Pat. 
No. 2,267,181 to Wildhaber. This approach enables a single rotary cutter 
to produce gears having different variations in profile curvature along 
the length of the teeth. Varying the feed rate of the rotary cutter 
relative to the gear controls the profile curvature. This concept may also 
be applied to the roughing blades thus requiring relative translational 
movement between the rotary cutter and gear during the roughing operation. 
Roughing blades having slightly relieved circular arcuate side surfaces are 
known from U.S. Pat. No. 2,327,296. Each side comprises a singular 
circular arc profile and the purpose of the relieved side surface is to 
prevent side surfaces of the blades from contacting the tooth profiles 
formed by the preceding roughing blades thus avoiding rubbing of the 
blades on the tooth slot being cut. Only the juncture of the sides with 
the tip and the tip itself actually remove stock material from the gear. 
In view of the speed at which rotary disc cutters remove stock material 
from gear blanks, wear, due to increased heat at the cutting surfaces, is 
a major concern. Metal chips packing between successive blades may also 
occur if the shape of the removed chip is not correct or if not enough 
fluid is present to wash the chips away from between the blades. Metal 
chips that collect between successive cutting blades may become hot due to 
the heat generated by the rapid cutting speed and the heat, in turn, may 
cause the chips to bond to one another and to the cutting blades. 
It is an object of the present invention to reduce or eliminate the 
above-mentioned problems without sacrificing the speed of the cutting 
process. 
It is another object of the present invention to provide a cutting blade 
that permits improved cooling of the cutting surface thereof and enhances 
the removal of metal chips from the vicinity of the blades. 
A further object of the present invention is to reduce the costs involved 
with cutter production while extending the useful life of a rotary disc 
cutter due to less wear and chip packing during the cutting process. 
SUMMARY OF THE INVENTION 
In the present invention, a relief surface is included on part of the side 
surface of at least a portion of the plurality of blades, preferably the 
roughing blades, arranged about the periphery of a rotary disc cutter. The 
relief surface allows a clearance to be formed between the relief surface 
and the surface of a workpiece. The clearance is of a dimension to allow 
the flow of coolant therethrough, thereby improving the cooling of the 
cutting surfaces of the blades, and provide for increased amounts of 
coolant to wash metal chips away from the cutting blades. 
A rotary disc cutter comprises a plurality of blades arranged about the 
periphery thereof. Each blade comprises a tip and two sides. In at least a 
portion of the plurality of blades, the sides of each blade comprise first 
and second side portions with the first side portion having an outermost 
edge coextensive along the thickness of the blades with the tip of the 
blade. The first side portion and the tip comprise the "cutting surface" 
of the blade. The second side portion is, in turn, coextensive along the 
thickness of the blade with an innermost edge of the first side portion. 
The second side portion is relieved from the first side portion. The first 
and second side portions define a piecewise surface and the profile of the 
piecewise surface is one of intersecting segments such as two curves. 
Either or both of the first and second side portions may be circular arc 
surfaces thus having circular arc profiles.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The details of the present invention will now be discussed with reference 
to the accompanying Drawings which represent the invention by way of 
example only. 
The general form of a rotary disc cutter is shown in FIG. 1. The cutter 
comprises a circular body portion 1 with a plurality of individual cutting 
blades arranged on segments 17 and spaced from one another about the 
periphery of the body portion 1. Each blade included in each segment 
comprises a front surface or "face" 32 and a back surface 33, two sides 
and a tip or end 34. Each blade is inclined forward. A cutting edge is 
formed at the intersection of the sides and tip with the front surface 32. 
In FIG. 1 the rotary cutter comprises a series of roughing blades 2, 
formed on separate segments 17, extending in a clockwise direction from 3 
to 4, a single segment of semi-finishing blades 18 and separate segments 
17 of finishing blades 5, extending from 6 to 7. Each successive roughing 
blade of the series is longer than the previous blade to enable each 
successive blade to cut deeper into a workpiece to the desired depth of 
cut. The gap 8 located between the last semi-finishing blade at 18 and the 
first finishing blade at 6 is the location for attaching a deburring tool 
(not shown) for removing burrs from the end of a tooth slot subsequent to 
roughing and semi-finishing. Roughing, semi-finishing and finishing blades 
are formed integral with the plurality of segments 17 and the segments are 
secured about the periphery of the body portion 1. It can be seen in FIG. 
1 that there are about five cutting blades located integral with each of 
the segments 17. The gap 9 is an indexing gap which allows the work gear 
to be rotated to the next tooth slot position when the gap 9 is abreast 
the gear blank. A keyway 31 is located in the body of the cutter to 
facilitate placement of the rotary cutter on a cutting machine. 
In operation, the roughing blades 2 engage a gear blank and due to their 
successively increasing height, cut successively deeper into the blank to 
the desired depth of cut. At this point blades from 3 to 4 have engaged 
the work gear. Typically, as stated in the "Background of the Invention" 
above, roughing blades are designed with circular arc side surfaces with 
all side surfaces having the same center of curvature. During roughing 
there is usually no relative motion between cutter and work gear. 
Therefore, the surface formed on the tooth surface is complementary to the 
surface on the roughing blades. Since roughing blades surfaces are 
normally concave circular arcs the complementary surface on the tooth 
would therefore be a convex circular arc. Roughing blades are narrower 
than finishing blades in order to leave sufficient metal on the tooth 
surfaces to be removed by the finishing blades. 
Generally following the last roughing blade at 4 there is a segment of 
semi-finishing blades 18. These blades are the same width as the roughing 
blades and their purpose is to form a surface similar to the finished 
surface thus reducing the amount of stock material remaining on the tooth 
surface for removal by the finishing blades. As these blades engage the 
work gear the rotary cutter is translated relative to the work gear 
through the tooth slot thus producing a surface similar to the desired 
finished surface. Semi-finishing blades are generally all of the same 
height. The side surface profiles of the semi-finishing blades are usually 
comprised of the same circular arc but with the center of the arc being at 
different positions, for example along a straight line, for each 
successive blade. 
After deburring by a tool (not shown) located at 8 the first finishing 
blade at 6 engages the work gear and as the finishing blades rotate 
through the tooth slot the rotary cutter is translated relative to the 
tooth slot in the reverse direction of the semi-finishing motion. Thus it 
can be seen that after final finishing blade at 7 passes from the tooth 
slot, the rotary cutter will be back at the position for roughing. At this 
point the indexing gap 9 is abreast the work gear thus allowing the work 
gear to be indexed to the next slot position. As stated above, finishing 
blades are wider than the roughing and semi-finishing blades and are 
typically all of the same height with side surface curvature varying 
depending upon the type of surface desired. Examples of different side 
surfaces were discussed in the "Background of the Invention". 
It is the roughing blades which are the primary focus of the present 
invention. FIG. 2, enlarged to show detail, illustrates a conventional 
roughing blade 10 in position for cutting a portion of tooth slot 16 
between adjacent teeth 19 on a work gear. The blade 10 comprises an end or 
tip 12 and sides 11. 
FIG. 3 illustrates an enlarged view of two successive conventional roughing 
blades: the previously discussed blade 10, represented by dashed lines, 
and blade 13 for cutting a portion of a tooth slot 16 between adjacent 
teeth 19 on a work gear. It is to be understood that blades 10 and 13 do 
not pass a particular location in the tooth slot 16 simultaneously. Blades 
10 and 13 pass through the tooth slot successively as do all blades of a 
rotary disc cutter. FIG. 3, as well as any other Figures illustrating a 
plurality of blades at a particular cross-sectional location of a tooth 
slot, is intended to show the position of each illustrated blade as it 
passes a particular location in a tooth slot. These Figures are for 
comparative purposes of the cutting positions of the illustrated blades 
and are in no way intended to suggest simultaneous cutting by a plurality 
of blades at a particular cross-sectional location of a tooth slot. 
In FIG. 3 it can be seen that blade 13 comprises sides 14 and tip 15. It 
can also be seen that although the sides 14 of blade 13 extend from the 
tip 15 to the top of the teeth 19, only the portion of the sides 14 that 
extends from the tip 15 to the location 24, which is the location to where 
previous blade surfaces 11 and 12 have cut, actually remove material from 
the tooth slot 16. The portion of the sides 14 which extend from location 
24 to the top of teeth 19 merely pass over tooth surfaces that have 
already been cut by previous blade 10 and any number of blades preceding 
blade 10. Therefore these portions of the blade sides do no actual cutting 
as there is no stock to be removed from that portion of the tooth surface. 
It can therefore be seen that, when considering all roughing blades, only 
the tip and that portion of the sides which extends beyond the length of 
the preceding blade, actually remove stock material from the slot of a 
work gear, with the exception, of course, of the first roughing blade 
which has no preceding roughing blade. 
Side surfaces of roughing blades rubbing already cut tooth surfaces was 
addressed in previously discussed U.S. Pat. No. 2,237,296. FIG. 4 
illustrates an enlarged view of the disclosed blade form of that patent 
wherein a blade 20 is shown having a tip 21 and sides 22. The sides 22 of 
the blade 20 are slightly relieved from being complementary with tooth 
surfaces 19. The amount of relief is shown at 23. The relief thus prevents 
rubbing of the blade side surfaces 22 on the side surfaces of the teeth 
19. In this embodiment, however, it can be seen that only the tip would be 
cutting the desired width of the tooth slot 16. The side 22 of this 
particular arrangement would do little cutting along the desired surface 
of the tooth. It is also evident that as successive blades engage tooth 
slot 16, stepwise portions of stock material will be left on the tooth 
sides. The stepwise portions representing material remaining between 
successive blades due to the relief surfaces. The stepwise portions of 
stock material will be discussed further below. 
A roughing blade, enlarged to more clearly show detail, according to the 
present invention is illustrated in FIG. 5. The blade 25 comprises front 
face 67, tip 26 and two sides 27. Each side 27 comprises a first side 
portion 28 and a second side portion 29. The outermost edge 65 (as viewed 
radially outwardly from the axis of the cutter) of the first side portion 
28 is coextensive along the thickness, extending between the front and 
back surfaces of the blade 25, with tip 26. The second side portion 29 is, 
in turn, coextensive along the thickness of the blade 25 with the 
innermost edge 66 of the first side portion 28. Tip 26 and first side 
portion 28 form what will be referred to as the "cutting surface" of the 
roughing blade 25. The cutting edge is formed at the intersection of the 
front face 67 of the blade with the tip 26 and the first side portion 28. 
The profile shape of first side portion 28 may be any desired shape, for 
example a circular arc, and is generally complementary to the respective 
desired surface of the gear tooth to be cut. Second side portion 29 is 
relieved away from the first side portion 28 and is therefore spaced or 
relieved from the surface of the tooth. The amount of relief is of a 
dimension sufficient to allow coolant to flow therethrough to improve the 
cooling of the cutting surface and enhance the flow of metal chips away 
from the cutting blade. 
FIG. 6 shows blade 25 of the present invention (enlarged to show detail) in 
position for cutting a tooth slot 16 between adjacent teeth 19 of a work 
gear. It is seen that tip 26 and first side portions 28 cut bottom and 
side surface portions, respectively, of the teeth of the work gear. These 
portions 26 and 28 of blade 25 represent the amount of blade 25 that 
extends beyond the previous roughing blade. The location 24 is the 
location on the tooth 19 to which the blade preceding blade 25 has 
previously cut. Just as in FIG. 3, it can be seen that the side surfaces 
of the teeth 19 extending from location 24 to the top of teeth 19 have 
been previously formed by preceding roughing blades. Therefore, 
maintaining the side surface of the blade 25 complementary to the side 
surface of the work gear beyond location 24 accomplishes no stock removal 
during cutting since stock material in this area has already been removed 
by previous blades. Applicants have discovered that by relieving the 
portion of a cutting blade that extends through the tooth slot space 
occupied by previous blades, no cutting efficiency is sacrificed. In fact, 
the cutting efficiency is unexpectedly increased due to the increased 
amount of coolant that can pass through the space 30 between the relieved 
surface 29 and the surface of the gear teeth 19. The increased amount of 
coolant improves cooling and therefore extends the useful life of the 
cutting surfaces 26 and 28. The increased coolant also enhances the flow 
of metal chips from the vicinity of the blades thus limiting the 
occurrences of chips packing between successive cutting blades. 
FIG. 7 illustrates, in an enlarged manner, a comparison of a blade 20 
according to prior art as illustrated by FIG. 4 and a blade 25 according 
to the present invention. It can be seen that the clearance 23 of the 
prior art, intended only to prevent rubbing of the gear side surfaces, is 
significantly narrower than the clearance 30 of the present invention. The 
prior art clearance 23 would allow little, if any, coolant to pass 
therethrough thus preventing cooling of the tip 21. However, the clearance 
30 of the present invention is of a dimension to allow the flow of coolant 
therethrough whereby the cooling of the cutting surfaces 26 and 28 is 
improved. For example, the width of the clearance 30 near the top of the 
tooth 19 may be up to about 0.125 inches or more, the upper limit being 
dependent, for example, on the amount of blade material required to 
withstand operational conditions. 
FIG. 8 illustrates a comparison, also enlarged, of successive prior art 
blades 50, 55 and 60 and successive blades 35, 40 and 45 according to the 
present invention. The prior art blades 50, 55 and 60 comprise respective 
sides 52, 57 and 62 that are relieved along the entire length thereof. 
This type of relief causes residual stock material to be left on the tooth 
sides which in turn increases the amount of material that must be removed 
by the semi-finishing or finishing blades resulting in excessive wear and 
shortened life for these blades. The residual stock material is arranged 
in a stepwise manner as shown by 58 and 63. Decreasing the distance 
between blades, and thereby increasing the number of blades, does not 
eliminate the residual stock removal. As a matter of fact, only when the 
number of blades approaches infinity would the distance between blades 
approach zero and the amount of residual material also approach zero. Of 
course, this approach is impractical. 
Looking at inventive blades 35, 40 and 45 of FIG. 8, the occurrence of 
residual stock material is eliminated by the blade form of the present 
invention. The side surfaces of the blades are comprised of two portions, 
for example, circular arc profiled, arranged in a piecewise manner. Of the 
three blades shown, blade 35 would be the first blade to cut in the slot 
16. Blade 35 includes tip 36 and first side portion 37 the outermost edge 
(as viewed radially outwardly from the axis of the cutter) of the first 
side portion 37 is coextensive along the thickness of the blade with the 
tip 36. These surfaces, 36 and 37, are precisely ground in order to 
produce the desired, generally complementary, surface on the gear tooth. 
Surfaces 36 and 37 also have the appropriate cutting edge formed at their 
intersection with the front face of the blade. Blade 35 also includes 
second side portion 38 which is relieved from complementarity with the 
surface of gear tooth 19. Second side surface 38 is coextensive along the 
thickness of the blade with the innermost edge of the first side portion 
37 and extends from location 34, which is the location to which the blade 
immediately preceding blade 35 has cut, to approximately the top of the 
tooth 19 where it intersects the body portion of the blade segment. Second 
side portion 38 is relieved a significantly greater amount than the 
clearance 5 of the prior art. The amount of clearance 39 is of a dimension 
to allow the flow of coolant therethrough to improve the cooling of the 
cutting surfaces 36 and 37 and also to enhance the flow of metal chips 
away from the cutting blades. 
Immediately following blade 35 is blade 40, illustrated by dashed lines, 
which comprises tip 41 and first side portion 42. As in all of the 
roughing blades of the present invention, the tip and the first side 
portion form the cutting surface of the blades. First side portion 42 
extends from its intersection with tip 41 to the location 44 on tooth 19 
which represents the location to which the preceding blade 35 has 
previously cut. The curvature of surface 42 is generally complementary to 
the desired surface of the tooth 19. Beyond location 44 the desired 
roughed surface has already been formed by previous blades. Therefore, it 
is at this point, or slightly beyond in order to create a small overlap, 
that the relief surface 43 begins. Again it can be seen that the clearance 
created is much greater than that contemplated by the prior art. 
Blade 45, illustrated by dotted lines, immediately follows blade 40. As 
with the previous blades, a cutting surface is defined by tip 46 and first 
side portion 47. First side portion 47 extends from the tip 46 to location 
49 which is the location to which preceding blade 40 has already cut. 
Located beyond location 49 is second side portion 48 which is relieved 
from the tooth surface 19. Location 64 is the location to which blade 45 
cuts and is the location to which the first side portion of the next blade 
would extend. 
By including the first side portions 37, 42 and 47 on successive blades 35, 
40 and 45 respectively, residual stock material on the roughed tooth 
surfaces is eliminated and a desired profiled surface, for example a 
substantially circular arcuate profile, is formed on the teeth 19. There 
is no stepwise arrangement of stock material on the tooth surfaces, such 
as shown at 58 and 63 of the prior art, after rough cutting with the 
rotary cutter of the present invention. Moreover, with the present 
invention, cooling of the cutting surfaces is enhanced as is the flow of 
metal chips from the vicinity of the blades. An additional advantage is 
that since the relieved surfaces do no cutting, the surfaces do not 
require precision grinding nor is the formation of a cutting edge 
necessary at the intersection of the relieved surfaces with the front face 
of the blade. This advantage amounts to a considerable cost savings due to 
the reduced grinding time that is required. 
Relief surfaces may be of any form which permits the flow of coolant 
therethrough such as a circular arc. In FIG. 8, relief surfaces 38, 43 and 
48 are circular arcs of substantially the same curvature but having 
centers spaced along a line extending radially of the cutter axis and 
containing the center of curvature of the first side portions 37, 42 and 
47. 
The rotary cutters of the present invention may comprise only roughing 
blades or, preferably, may have a plurality of blades located about the 
periphery thereof comprising roughing blades, semi-finishing blades and/or 
finishing blades. With the latter type of cutter, a gear tooth slot will 
be completely finished with one rotation of the cutter. 
FIGS. 9a, 9b and 9c illustrate alternative blade tip configurations of the 
present invention. The Figures have been enlarged and exaggerated to show 
detail. FIG. 9a shows a blade 70 comprising first side portion 71 and 
second side portion 72 and a substantially concave-shaped tip or end 73. 
The concave-shaped tip 73 may be formed by conventional grinding processes 
having fixed abrasive wheels whose circular grinding surface imparts a 
concave shape to the blade tip. 
However, with the advent of computer numerical control (CNC) grinding 
machines, any desired shape may be obtained on the blade tip. FIG. 9b 
shows a blade similar to FIG. 9a except that the blade tip configuration 
74 is substantially convex-shaped. The convex-shaped blade tip 74 enhances 
the ability of metal chips to roll from a workpiece, that is, the metal 
removed by such a blade tends to roll into a tightly curved generally 
spiral-shaped configuration which significantly reduces chip packing in 
the spaces between blades. Metal chips removed in such a manner reduce the 
stress on a cutting blade thus extending the useful life thereof. The 
convex-shaped blade tip 74 also results in improved cutter action since 
the tip does not impact across its entire width instantaneously. Instead, 
impact takes place outwardly from the center of the tip thus increasing 
the impact time and resulting in smoother cutting. 
FIG. 9c illustrates another similar blade 70 having sides 71 and 72 wherein 
the tip configuration 75 is substantially a planar surface. As with 
convex-shaped blade tips 74, points of inflection 76, normally found in 
concave-shaped blade tips 73, are eliminated with the result being a 
stronger cutting blade. A single rotary cutter may comprise more than one 
blade tip configuration. For example, all three of the abovediscussed 
blade tip configurations may be present on a single rotary disc cutter 
according to the present invention. 
FIG. 10 illustrates an alternative rotary cutter according to another 
aspect of the present invention. In this embodiment, the many segments 17 
shown in FIG. 1 have been replaced by substantially larger segments 80, 
81, 82 and 83. By replacing the plurality of smaller segments 17 by 
significantly fewer larger segments, many of the seams between the 
segments, illustrated by 84, for example, are eliminated thus increasing 
the rigidity of the rotary cutter. Any movement of the blades is greatly 
restricted by eliminating many of the areas where movement may occur. The 
larger segments also permit quicker assembly of the rotary cutter since 
the number of time consuming checks for proper seating of the segments 80, 
81, 82 and 83 on the cutter body 1 are reduced due to the lesser number of 
blade segments. 
Segments 80, 81 and 82 comprise roughing blades 2, in accordance with the 
present invention, arranged about the periphery of the rotary cutter in a 
clockwise direction extending from 3 to 4. The last several blades, for 
example generally five, of segment 82 may be semi-finishing blades. 
Following the deburring gap 8, all of the finishing blades 5, extending 
from 6 to 7, may be located on one segment 83. Generally, no more than 
about five segments are desired for the roughing and/or semi-finishing 
blades with no more than three segments being preferred and no more than 
about two segments are desired for the finishing blades with one segment 
being preferred. However, the rotary disc cutter comprising the roughing 
blades of the present invention may also be formed from a solid metal 
disc, such as a casting of cutting tool steel, whereby the need for 
segments, comprising blades and attached to the cutter body, would be 
nonexistent. A rotary disc cutter 90 formed from a solid metal disc is 
illustrated in FIG. 11. 
The rotary cutter of the present invention may be formed by first providing 
at least one circular arc segment, either small, 17, or large, 80, 81, 82 
and 83, for example, in substantially the desired or "roughed" form. This 
includes providing the blade forms, spaces or gashes between successive 
blades and mounting surfaces on the segments for attachment to the cutter 
body 1. This step is generally carried out on a grinding machine, 
preferably a CNC grinding machine. A roughing blade form comprising a tip 
and two sides each having first and second side portions according to the 
present invention is first formed on the blade segment blank. The formed 
segment is then gashed to form the individual blades of the segment. 
Smaller segments 17 may have about five blades per segment while larger 
segments such as 80 may have about fifteen or more blades per segment. 
Gashing forms the spaces between successive blades, thus it can be seen 
that the front face of one blade and the back surface of an adjacent blade 
are simultaneously formed by gashing. Also, the mounting surfaces are 
formed on the segment. The mounting surfaces are the surfaces which 
contact the cutter body when the rotary disc cutter is assembled. The 
segment may then be hardened by heat treating. 
The mounting surfaces of the segment may be finished to their desired 
dimensions, preferably by grinding. After the mounting surfaces are 
formed, the roughed segments are then mounted on a grinding head, which is 
shaped substantially the same as the cutter body 1, and the blades 
surfaces are finish ground to their final form. However, with the roughing 
blades of the present invention, only the tip and the first side portion 
require finish grinding to form a finished surface. Since the relieved 
second side portion does not contact the workpiece it does not require a 
finished surface to be formed thereon. Therefore, the surface formed by 
the initial rough-forming operation is sufficient for the second side 
portion. It can be seen that the reduced amount of finish grinding offers 
a significant cost and time savings when producing the rotary disc cutters 
of the present invention. Finally, the front face of the blades are 
finished, preferably by grinding, in order to form a cutting edge at the 
intersection of the front face with the tip and the first side portion. Of 
course, the semi-finishing and finishing blades are formed according to 
the particular application of the rotary cutter. These blades have cutting 
surfaces along their entire tip and sides with the curvature of the side 
being dependent upon the type of gear to be cut or the specific tooth 
profile desired as was previously discussed in the "Background of the 
Invention". 
If a solid disc is utilized there will be no segments that require forming 
and therefore the blades may be rough formed, gashed and finished on the 
solid disc. 
The present invention offers increased efficiency combined with decreased 
production costs for rotary disc cutters. The blade side configuration 
comprising two side portions enables the required stock material to be 
removed from the surface of a gear tooth while providing for increased 
amounts of coolant to reach the cutting surfaces of the blade and wash 
chips away from the vicinity of the blades. Finish grinding is needed only 
on one side portion thus representing a cost and time savings since there 
is no need to finish grind the entire surface of the sides of the blades. 
While the present invention has been described with reference to preferred 
embodiments it is to be understood that the invention is not limited to 
the particulars thereof. The present invention is intended to include 
modifications which would be apparent to those skilled in the art to which 
the subject matter pertains without deviating from the scope and spirit of 
the appended claims.