US1982036A - Method of producing gears - Google Patents

Description

1934- E. WILDHABER 1,982,036

METHOD OF PRODUCING GEARS Filed March 25, 1951 2 Sheets-Sheet l l I I 13 10 &K

INVENTOR Nov. 27, 1934. E. WILDHABER METHOD OF PRODUCING GEARS Filed March 23, 1951 2 Sheets-Sheet 2 INVENTOR ills ATTOR Patented Nov. 27, 1934 UNITED STATES 1,982,036 METHOD OF PRODUCING GEARS Ernest Wildhaber, Brooklyn, N. .Y., assignor. to

Gleason Works, Rochester, N. Y., a corporation of New York Application March 23, 1931, Serial No. 524,633

25 Claims.

The present invention relates to the production of bevel and hypoid gear pairs of the type where one member of the pair is cut in a forming or non-generating operation and the other member is generated, and the invention relates more particularly to the production of bevel and hypoid gears of this character which have skew or longitudinally curved teeth.

Insofar as this invention relates to the produc- 10 tion of hypoid gears, it may be regarded as an improvement over the method of my Patent No. 1,622,555 of March 29, 1927.

Gear pairs in which one member is non-generated can. be out faster and more cheaply than pairs in which both members are generated. A gear can be out faster if no generating roll is required than if a generating roll must be used, while a gear-generating machine is more complicated in construction and operation than one intended to do form-cutting only. These advantages have been realized for years,yet gear pairs of the character described have never come into use on a commercial scale. Difficulties in production, which will be outlined below,'have heretofore more than offset the manifest advantages of this type of gearing.

Bevel and hypoid gears should have teeth tapering in depth from their outer to their inner ends for reasons of mesh, and, also, in order to obtain requisite strength at the small ends of the teeth. Moreover, it is desirable in gear cutting to use straight-sided cutting tools because of their simplicity and the accuracy with which they can be produced and, also, because of the suitable 35 tooth shapes which can be obtained with such tools.

Heretofore when gear pairs were cut in which one member was non-generated, the other member was always generated in an operation in which tool and blank were rolled relative to one another as though the blank were rolling on the mate nongenerated gear, the basic theory being that thus the generated member would be conjugate to the non-generated gear and the two would run correctly together. However, when either skew or curved tooth bevel or hypoid gear pairs, containing one non-generated member, were cut in this way with teeth of tapering depth andwith straight-sided cutting tools, a highly objectionable bias bearing condition has been obtained. Bias bearing is atooth bearing or area of tooth surface contact that extends diagonally across the mating side tooth surfaces of a pair. It causes the gears to be noisy and results in uneven distribution of tooth loads. It is due to mismatch of the pressure angles of mating tooth surfaces of the gears.' f 7 To retain the benefits and advantages of the form cutting process and avoid bias bearing, it has been necessary heretofore,- either to cut the gear pairs with teeth of parallel depth. or with spherical tooth surfaces. Tapered gears: which haveteeth of parallel depth, that is, of uniform tooth height from endtoend are, however, weak at their small ends because, for one reason, the small ends of the teeth are of excessive height in proportion to thickness. Hence, the parallel depth method of cutting has not proved satisfactory for it avoids bias bearing only at the sacrifice of tooth strength. By use of spherical cutters, gears of the character referred to can be cut with teeth of tapering tooth depth and without bias, but this method is restricted to the cutting of longitudinally curved teeth and the tools used must have cutting edges of circular are profile accuratelycentered on the axis of rotation of the tool. The spherical cutting method has consequentlynot proved satisfactory, either, for it avoids bias bearing only at the sacrifice of simplicity. I i

The purpose of the present invention is to provide a simple method of cutting bevel and hypoid gearsof the character referred to with teeth of tapering depth and without bias bearing and while employing straight-sided cutting tools. The new steps involved in the present invention are not limited, however, to cutting withstraightsided cutting tools or, in fact, to cutting teeth of tapering depth. I

With the present invention, one member of the pair, preferably the larger member, is form-cut or non-generated as heretofore, but the pinion instead of being generated conjugate to its mate gear is generated conjugate to an imaginary gear differing from the mate insuch manner that the pinion will mesh with its mate without bias bearing and still transmit uniform motion.

In the drawings:

Figures 1 and 2 area sectional view and a bottom plan view, respectively, illustrating diagrammatically the preferredmethod employed with this invention of cutting the gear or nongenerated member of a pair of longitudinally curved tooth bevel or hypoid gears;

Figures is a diagrammatic view, showing the difficulty heretofore experienced in cutting gear pairs of the character referred to with teeth of tapering depth;

Figure 4 is a plan view and Figure 5 a part elevational and part sectional view illustrating bias bearing will be obtained.

bearing may be obtained.

' ing, according to this invention, the mating pinion of a bevel gear pair; and v Figure 8 is a diagrammatic plan view illustrating specifically how the opposite sides of the teeth of a longitudinally curved tooth hypoid pinion may be generated, according to a preferred embodiment of the present invention, conjugate to different gears so that when the pinion is in mesh with its mate gear a localized tooth The invention will, for the sake of illustration, be described in connectionwith the production of longitudinally curved tooth gears with a face mill cutter, but it applies broadly to gears having longitudinally inclined teeth and is not, .of course, limitedas to the type of tools employed in the cutting of the gears.

Figures 1 and 21illustrate the cutting of the nongenerated member G of a pair. 10 designates the cutting tool whichis a conical face-mill gear cutter having "straight-sided cutting edges Hand 12 inclined to the axis 13 of the cutter in accordance with thepressure'angle of the teeth tobe cut in'the gear blank. In operation, the axis 13 of thecutter is inclined to the axis 14 of the blank so asto cut teeth T in the blank of tapering depth asindicated in Figure 1 and, as in previous methods of cutting these gears, the tooth'spacesof the blank are cut by simply feeding the rotary cutting tool 10 into depth. Thus, the tooth surfaces of the gear are exactly complementary to the edges of the cutting tool. No generating roll is employed.

The cutting tool 10 may be a standard face mill gear cutter, in which case 'theblank' will be indexed after the cutting of each tooth space and the tooth spaces of the blank will be completed successively, or it may be aface mill hobbing cutter in which case the blank will have a continuous indexing rotation and all of the tooth spaces of the blank'will be operated on simultaneously. f

-Heretofore, as stated above, the production of gear pairs in which one member is non-generated has always been associated with the idea that the, other member shouldbe generated in a process in which the cutting tool represents the mate gear and the tool and blank are rolled together as thoughthe blank were rolling on the mate gear. But, as stated-abovethis method produces a bias-bearing when the pair is cut tapering depth with straight -sided cutting tools.

Thereason is obvious: The-cutter that cuts the but the root and tip surfaces of the gear-teeth are inclined to one another because the teeth are of tapering depth. Therefore the pressure angles of gear and pinion will not match along the mating tooth surfaces and=the conditionof Figure 3 illustrates the difliculty resulting from the method of generation heretofore employed, particularly'as encountered-in the cutting of longitudinally curved tooth bevel and hypoid gears with straight-sided face mill cutters. This figure is a view of the plane 16 tangent at a mean point of contact 0 to the mating tooth surfaces of a pair out according to prior practise and having teeth of tapering depth. 18 denotes a portion of the common pitch line of the mating tooth surfaces. 19 denotes the line of contact between the tangential plane 16 and the conical cutting surface of the gear cutter, while 20 denotes the line of contact between said tangential plane 16 and the conical cutting surface of the pinion cutter. each cut tapering depth, .the two lines 19 and 20 will not coincide. but will be inclined at a slight angle to each other, and because of the inclination of the two lines 19 and 20, the conical cutting surfaces of the gear and pinion cutters will not produce matching tooth surfaces on gear and pinion. When a pair was produced according to the prior practise, therefore, with teeth of tapering depth by th'euse of "straight-sided face mill cutting tools, outside of the mean contact Because the gear and pinion are point'O, the tooth surfaces 'of gear and pinion were not conjugate.

, The mismatch orerror was present, also, in varying degrees in longitudinally curved tooth gears of the character described cut with other types of tools and in skew bevel andhypoid gears of the character described, also. I

' With the method of the present invention, the

pinion'is generated conjugate to a gear other than axis of thisgear is indicated at22. Ordinarily the cone radius of the generating gear G will be different from the cone radius'of the mate gear G so that the axis22 of the generating gear will be offset from the axis 14 of the'mate gear, as shown; Ordinarily, too, the axis 25 of the pinion will be oifset'from the axis 22 of the generating gear, G, during generation, a distance Y different from the distance X of ofiset between the axis of the pinion and the axis 14 ofits mate gear G when the two are in mesh. Preferably, however, the axis of the pinion will bein clined to the axis 22 of thegenerating gear G, during generation, at the same 'angle as the axis 25 of the'pinion is inclined to the axis 14 of'its mate'gear G when in mesh with the mate gear. Inthe drawings, this angleis; v

The cutter 23 which is employed to generate the tooth surfaces of the pinion represents the imaginary generating gear G and is positioned with its axis 24 inclined to the axis 2 5 of the pinion blank to' produce "teeth of tapering depth in the-blankl Thecutter has straight sided cutting edges 26 and 2'] and may be of standard construction or" of the face mill hobbing type.

-' under varying conditions.

22 of the imaginary generating gear G while the blank H rotates on its axis 25, or all of the roll may be on the work, in which case, the cutter will be stationary except for its rotation and the blank will both rotate on its axis 25 and be simultaneously swung about the axis 22 of the imaginary generating gear G or thirdly, all the roll may be on the tool, as will be understood by those skilled in the art.

The invention is applicable, also, to the generation of bevel pinions. This is illustrated in Figures 6 and 7. B indicates the bevel pinion blank, and G", the gear to which the pinion is generated conjugate. This gear G" differs from the gear G with which the pinion B is to mate by an amount necessary to com'pensate for the mismatch of the tooth surfaces of gear and pinion which would otherwise result from the taper in depth of the teeth of the pair when out with a face mill cutter having straight-sided cutting edges. The axis of the generating gear G is indicated at while the axis of the gear with which the pinion B is to mesh is denoted at 31. It will be seen that the axis 30 of the generating 3 gear G intersects the axis 32 of the pinion B in a point offset from the apex 33 of the pinion blank.

To generate the bevel pinion B to run with a longitudinally curved tooth non-generated gear such as a gear G, a cutter 37 is employed which has straight-sided cutting edges 38 and 39. The axis 40 of this cutter is inclined to the axis 32 of the pinion blank so as to cut teeth of tapering depth in the blank and so as to represent tooth surfaces of the generating gear G". The cutter 37 is rotated on its axis 40 and simultaneously a relative rolling movement is produced between the cutter and the pinion blank B as though the pinion blank were rolling on the gear G. As before, in this operation the roll may be divided, or all of the roll may be applied to the work or all to the cutter. Preferably the generating gear G" is so chosen that its axis 30 is inclined to the axis 32 of the pinion at the same angle as the axis 32 of the pinion is inclined to the axis 31 of its mate gear when in mesh. In the drawings, this angle is 90. It will be understood that a certain amount of liberty may be exercised in the choice of the generating gear, as may be required Thus the bevel pinion blank 13 might not only be positioned so that its apex is offset from the axis 30 6f the generating gear G but, also, so that its axis 32 is offset from the axis 30. f

The choice of the generating gear G or G for hypoid or bevel pinion generation can be determined. mathematically, but is a matter of in volved computation. The choice of the generating gear can be determined experimentally in a comparatively simple way. A tool C is first selected (Figure 8) which will produce tooth surfaces of the desired curvature on the pinion blank to mate with. the tooth surfaces cut in the mating non-generated gear. This tool is then positioned relative to the pinion blank D as if to represent a tooth side of the mating gear G, namely, a tooth side so positioned that a mean point 0 in its tooth surface will contact with a corresponding point in the mating tooth surface of the pinion. However, instead of rolling the tool C and pinion blank D relative to one another about the axis 14 of the mate gear G, they are rolled about an axis offset from the axis 14 of the mate gear and corresponding to the axis of a gear 47 to which the pinion D is to be generated conjugate. Usually the axis of the generating gear is assumed, as at 01 46, near the axis 14 and on the line 48-con'- necting the axis '14 with the mean contact pointO."-

The tool 0 then represents a tooth side of a gear 47 whosetooth surfaces have contact with the tooth surfaces of the pinion D when rotated at a slightly different ratio from theratio of rotation of the pinion D with its mate gearG. The roll or angular feed of the cutter C'or the gear blank D about the axis of the generating I gear 47 is increased over the rotation or angular feed of the gear G in the inverse ratio of the distances of the axis 45 or 46 and the axis 14 from the tooth normal N at the mean contact point 0. Under these conditions, tooth contact between'the mating tooth surfaces of the gear and pinion at the point 0 is maintained and uniform motion will be transmitted between the gear and pinion when in mesh. vi After generation, the pinion is run with its mate gear to test the tooth contact and it is then determined through visual inspection whether the assumption of the position of the axis 45 or 46 was correct and if not in which direction it. was off. If correction is necessary this can be effected easily by recutting the pinion.

Where it is desired to top-off and flank-out the tooth profiles of the pinion so as to reduce the area of profile contact or bearing, the axis 45 or 4.6 may be further displaced along a line 49 or a9, respectively, parallel to the tooth normal "NI Ordinarily, however, the axis of the generating gear 47 will be located on the line 4.8. The length of tooth bearing between the tooth surfaces of the pinion and the gear can be'controlled in a manner broadly similar to that now practiced in cutting spiral bevel and hypoid-gears. Thus, opposite sides of the pinion teeth may be cut conjugate to different generating gears. For instance, the convex sides of the pinion teeth may be cut with a tool having inside cutting edges of a radius less than the radius of the cut ting edges of the tool which cut the mating tooth surfaces of the gear, the axis'of the' generating gear being then located, for instance, at 45. The concave sides of -.the pinion teeth may then be cut with 'a cutter having outside cutting edges of increased diameter as compared with the out:

ting edges of the tool which cuts the mating tooth surfaces of the gear, the axis of the generating gear for these side tooth surfaces being then located, for instance, at 46. This method of cutting will providea desirable localization'of tooth bearing between the mating tooth surfaces of gear and pinion. 1

While the invention has been described in connection with the production of spiral bevel and hypoid gears and .pinions, with a particular type of tool, 'itis applicable broadly, also, to the production of bevel'an'd hypoid gears having longitudinally inclined teeth, such as skew teeth and the cutting tool employed may be of any type suitable for the cutting of the particular gears which it is desired to produce. pinion is generated, as described, with tooth surfaces of a lengthwise shape suitable to meshwith In general, the 1 the tooth-surfaces of themate non-generated gear and conjugate to a gear other than its mate to obtain a desirable tooth profile bearing. i

Thus, while I have described my invention in connection with particular embodiments, it will be understood that the invention is capable ofvarious further modifications and uses and that this application is intended to cover any variations,

uses, or adaptations of the invention, following, in general, the principles of the invention and including such departures from, the present disclosure as come within known or customary practice in thegear art and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. The method of producinga pair of tapered gears having teeth of tapering depth which comprises cutting the side tooth surfaces of one member of the pair in a forming operation by a relative depth-wise feed between the cutter and the gear blank, and cutting the side tooth surfaces of the other member of the pair in a generating operation in which the tool represents a tapered gear other than the mate gear and the tool and blank are rolled relative to one another as though the blank were rolling on such a tapered gear.

2. The method of cutting a pair of tapered gears having teeth of tapering depth which comprises cutting the side tooth surfaces of one member of the pair in a forming operation with a straight-sided cutting tool by a relative depthwise'feed between the tool'and the blank, and cutting the side tooth surfaces of the other member of the pair in a generating operation also with a straight-sided cutting tool by rolling the tool and blank relative to one another as though the blank were'rolling-on a tapered gear other than'its mate.

3. The method. of producing a pair of tapered gears which comprises cutting the side tooth surfaces of one member of the pair by positioning'a cutting tool and a gear blank relative to one another so that the tool will cut teeth of tapering depth in the blank and effecting a relative cutting motion between the tool and blank to produce teeth on the blank which are'longitudinally inclined to a generatrix of the blank while pro ducing a relative depthwise feed between the tool and blank to cutteeth of the proper depth, and cutting the side tooth surfaces of the other member of the pair by positioning a cutting tool and a gear blank relativeto one another so that the second tool will cut teeth of tapering depth in the second blank and effecting a relative cutting motion between the second tool and blank to produce teeth shaped longitudinally to mate with those of the first gear andproducing a relative rolling motion between the second tool and blank as though the second blank were rolling with a gear other than its mate to generate the tooth surfaces of the second gear.

. 4. The method of producing a pair of tapered gears which comprises cutting the side tooth surfaces of one member of the pair bypositioning a cutting tool having straight-sided cutting edges relative to a gear blank so .that the tool will cut teeth of tapering depth in the blank and effecting a relative cutting movement between the tool and blank to produce teeth on the blank which are longitudinally inclined to a generatrix of the blank while effecting a relative depthwise feed between the tool and blank to cut teeth of the proper depth in the blank, and cutting the side tooth surfaces of the other member of the pair by positioning a cutting tool having straightsided cutting edges relative to a second gear blank so that the second tool will cut. teeth of tapering depth in the second blank, and effecting a relative cutting motion between the second tool and blank to produce teeth on the second blank which are shaped longitudinally to mesh with those of the first gear and producing a relative rolling motion between the second tool and blank as though the second blank were rolling with a gear other than its mate to generate the tooth surfaces of the second blank.

5. The method of producing a tapered gear suitable to mesh with a non-generated tapered gear having teeth of tapering depth which comprisespositioning a cutting tool and a tapered gear blank relative to one another so that the tool will cut teeth of tapering depth on the blank and effecting a relative cutting movement between the tool and blank to produce teeth on the blank which are longitudinally inclined to straight generatrices of the blank, while simultaneously producing a relative rollingmotion between the tool and blank as though the blank were rolling on a gear other than its mate.

6. The method of producing a tapered gear suitable to mesh with a non-generated tapered gear having teeth of tapering depth which comprises positioning a cutting tool having straight-sided cutting edges and a tapered gear blank relative to one another so that the tool will cut teeth of tapering depth on the blank and effecting a relative cutting movement between the tool and blank to produce teeth on the blank which are longitudinally inclined to straight generatrices of the blank, while simultaneously producing a relative rolling motion between the tool and blank as though the blank were rolling on a gear other than its mate.

7. The method of producing a tapered gear suitable to mesh with a non-generated tapered gear having teeth of tapering depth which comprises positioning a-face mill cutting tool and a tapered gear blank relative to one another so that the tool will cut teeth of tapering depth in the blank and rotating the tool in engagement with the blank while producing a relative rolling motion between the tool and blank as though the blank were rolling on a gear other than its mate.

8. The method of producing a tapered gear suitable -to mesh with a non-generated tapered gear having teeth of tapering depth which comprises positioning a face mill cutting tool having straight sided cutting edges and a tapered gear blank relative to one another so that the tool will cut teeth of tapering depth in the blank, and rotating the tool in engagement with the blank while producing a relative rolling motion between the tool and blank as though the blank were rolling on a gear other than its mate.

9'. The method or producing a hypoid pinion suitable to mesh with a mating non-generated gear having teeth of tapering depth which comprises positioning a'face mill cutting tool and a pinion blank relative to one another so that the tool will cutteeth of tapering depth in the blank, and rotating the tool in engagement with the blank while producing a relative rolling move ment between the tool and blank about an axis offset from the axis of the blank a distance diiferent from the offset between the pinion and the mate gear whenin mesh.

.10. The method of producing a hypoid pinion suitable to mesh with a mating non-generated gear having teeth of tapering depth which comprises positioning a face mill cutting tool having straight-sided cutting edges and a pinion blank relative to one another so that the tool will-cut teeth of tapering depthin the blank and rotating the tool in engagement with the blank while producing a relative rolling movement between the tool and blank about an axis offset from the axis of the blank a distance diiferent from the offset between the pinion and its mate gear when in mesh.

11. The method of producing a. hypoid p' 'ion suitable to mesh with a mating non-generated gear having teeth of tapering depth which comprises positioning a tool and a pinion blank relative to one another so that the tool will cut teeth of tapering depth in the blank and effecting a relative cutting movement between the tool and blank to produce teeth on the blank which arelongitudinally inclined to straight generatrices of the blank while simultaneously producing a relative rolling movement between the tool and blank about an axis offset from the axis of the blank a distance different from the offset between the pinion and its mate gear when in mesh.

12. The method of-producing a hypoid pinion suitable to mesh with a mating non-generated gear having teeth of tapering depth, which comprises positioning a cutting tool having straightsided cutting edges and a pinion blank relative to one another so that the tool will cut teeth of tapering depth on the blank and effecting a relative cutting movement between the tool and blank to produce teeth on the blank which are longitudinally inclined to straight generatrices of the blank while simultaneously producing a relative rolling movement between the tool and blank about an axis ofiset from the axis of the blank a distance different from the offset between the pinion and its mate gear when in mesh.

13. The method of producing a hypoid pinion suitable to mesh with a mating non-generated gear having teeth of tapering depth, which comprises positioning a face mill cutting tool and a gear blank relative to one another so that the tool will cut teeth of tapering depth on the blank, and rotating the tool in engagement with the blank while simultaneously producing a relative rolling movement between the tool and blank about an axis offset from the axis of the blank a distance different from the offset between the pinion and its mate gear when in mesh, said axis being inclined to the axis of the blank at an angle equal to the angle between the axis of the blank and its mate gear when in mesh.

14. The method of producing a hypoid pinion suitable to mesh with a mating non-generated gear having teeth of tapering depth which comprises positioning a face mill cutting tool having straight-sided cutting edges and a gear blank relative to one another so that the tool will cut teeth of tapering depth on the blank, and rotating the tool in engagement with the blank while simultaneously producing a relative rolling movement between the tool andblank about an axis inclined to the axis of the blank at an angle equal to the angle between the axis of the blank and the axis of its mate gear when in mesh, but offset from the axis of the blank a distance different from the offset between the pinion and its mate gear when in mesh.

15. The method of producing a hypoid pinion suitable to mesh with a mating non-generated gear having teeth of tapering depth which comprises positioning a cutting tool and a pinion blank relative to one another so that the tool will cut teeth of tapering depth on the blank, and effecting a relative cutting movement between the tool and blank to produce teeth on the blank which are longitudinally inclined to straight generatrices of'theblank, while'siniultaneously producinga relative rolling movement between the tool and blank about an axis inclined to the axis of the blankat an angle equal to the angle-between the axis of the pinion and the axis of its mate gear when in mesh but offset from the axis of the blank a distance different from the offset between the pinion and its mate gear when in mesh. v E 16. The method of producing a hypoid' pinion suitable'to mesh with a mating non-generated gear having teeth of-tapering depth which com-' prises positioning a cutting tool having straightsided cutting edges and apinion blank relative to one another so that the tool will out teeth of tapering depth in the blank, and effecting a relative cutting movement between the tool and blank to produce teethon the blank which are longitudinally inclined tostraight generatrices of the blank, while simultaneously producing a relative rolling movement between the tool and blank about an axis inclined to the axis of the blank at an angle equal to the angle between the axis of the pinion and the axis of its mategear when in mesh but offset from the axis of the blank a distance different from the offset between the pinion and its mate gear when in mesh. .1,

1'7. The method of generating a tapered pinion which comprises cutting its side tooth surfaces by positioning a face mill cutting tool in engagement with a pinion blank so as :to cut teeth of tapering depth on the blank and rotating the cut-- ter in engagement with the blank while simultaneously producing a relative rolling movement between the tool and blank about an axis offset from the blank apex a difierent distance than the offset between the apex of the gear being generated and the axis of themate gear when mesh but inclined to the blank axis at an angle equal to the angle between the axis of the pinion and the axis of its mate gear when in mesh.

18. The method of generating atapered'pinion which comprises cutting its side tooth surfaces by positioning a cutting tool and a tapered pinion blank relative to one another so that the tool will cut teeth of tapering depth on the blank, and effecting a relative cutting movement between the tool and blank to produce teeth on the blank which are longitudinally inclined to straight gen'eratrice's the gear being generated and the axis of the mate gear when in mesh, but inclined to the blank axis at an angle equal to the angle between the axes of the pinion and its mate gear when in mesh.

19. The method of generating a longitudinally curved tooth tapered gear to mesh with a mate non-generated gear having longitudinally curved teeth of tapering depth which comprises employing different face mill cutters to cut the convex and concave sides of the teeth of the pinion, the cutter for cutting the concave sides of the teeth having a larger diameter than that employed for cutting the mating sides of the teeth of the gear, and the cutter for cutting the convex sides of the pinion teeth having a diameter smaller than that employed for cutting the mating sides of the gear teeth, and cutting the opposite sides of the pinion teeth with said cutters by positioning the appropriate cutter in engagement with the blank so that it will cut teeth of tapering depth in the blank, and rotating the cutter in engagement with the blank while producing a relative rolling motion betweenthe cutter and blank as though the blank were rolling on a gear other than its mate.- a

20. The method'of generating a'tapered pinion having longitudinally inclined teeth which comprises cutting its side tooth surfaces by imparting a cutting motion to a cutting tool while simultaneously producing a relative rolling motion between the tool and blank about an axis inclined to they blank axis at an angle equal to the angle between the axes of the pinion and its mate gear, when in mesh, and intersecting the blank axis in appoint oifset from the blank apex. V

21. The method of generating a tapered pinion having longitudinally inclined teeth suitable to mesh with the teeth of a non-generated tapered gear which comprises generating its opposite side tooth surfaces conjugate to different gears, each I tool and blank-are rolled relative to one another about an axis inclined to the axis of the blank at an angle equal to the angle between the axes of the pinion and its mate gear, when in mesh, but offset'a difierent distance from the apex of the pin- 1 ion than the axis of roll employed when generating the first-named side of the teeth;

7. 23. The method of producing a tapered gear suitableto mesh with a non-generatedjtapered gear having teeth of tapering depth which comprises positioning a cutting tool and a tapered gear blank relative to one another so that the tool will cut teeth of tapering depth on the blank and effecting a relative cutting movement between the tool and blank, to produce teeth on the. blank which are longitudinally inclined to straight generatrices of the blank while simultaneously producing, a relative rolling motionbetweenthe tool and blank. as though theblankflwere rolling on a gear other than its mate, the axis of the blank beingmaintainedduring said rolling motion at angle to the axis of the basic gear equal to the angle between the, axis of the gear being produced and itsmate, when inmesh.

24. The method of producing a pair of tapered gears having teeth of tapering depth from end to end which comprises cutting the side tooth surfaces of one member of the pair in a forming operation by effecting a relative cutting motion, between the tool and blank to produce teeth on the blank which are longitudinally inclined to a generatrix of the pitch surface of the blank and simultaneously producing a relative depthwise feed between the cutter and blank and cutting the side tooth surfaces of the other member of the pair'in a generating operation in which the tool is somoved as to produce teeth shaped longitudinally tomesh. with those of the first gear and the tool and blank are rolled relative to one another as though theblank were rolling on a tapered generating gear other than its mate,the axis of the second blank being maintained during said rolling motion at an angle to the axis of the generating gear equal to the angle between the axisof the gear being generated and its mate gearwhen in mesh.

25. The method of producing a pair of tapered gears havingteeth of tapering depth fromend to end which comprises cutting the side tooth surfaces of one member of the pair in a forming operation with a straight sided cutting tool by effecting a relative cutting motion between the tool and blank to produce teeth on the blank which are longitudinally.- inclined to a generatrix of the pitch surface of the blank and simultaneously producing a relative depthwise feed between. the tool and blank, and cutting the side tooth surfaces of the other member of the pair, also with;:a straight sided cutting tool, in a generatingoperation in which the tool is so moved as to produce .teeth shaped longitudinally to mesh with those of the first gearand the tool and blank. are rolled relative to one another as though the blank were rolling on a tapered generating gear other than its mate, the axis of the blank being maintained during said rolling mo tion at an angle to theaxis of thegenerating gear equal to the angle betweenthe axis of the gear being, generated and its mate gear when p in mesh. i V

ERNEST WILDHABER.

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