US1777135A

US1777135A - Method and machine for file grinding

Info

Publication number: US1777135A
Application number: US15592A
Authority: US
Inventors: Herbert L Bailey
Original assignee: Individual
Current assignee: Individual
Priority date: 1925-03-14
Filing date: 1925-03-14
Publication date: 1930-09-30
Anticipated expiration: 1947-09-30

Description

Sept. 30, 1930. H. L.. BAlLEY METHOD AND MACHINE FOR FILE GRINDING 7 Sheets-Sheet Filed March 14, 1925 Jhderdo HEREERT L. @AQLEY LWKMS Sept. 3 1930- H. BAILEY METHOD AND MACHINE FOR FILE GRINDING Filed March 14, 1925 7 Sheets-Sheet 2 Men/01:-

HERBERT' LBABLEY I Sept. 30, 1930. L BAlLEY I 1,777,135

METHOD AND MACHINE FOR FILE GRINDING mam? Baum 7 Sheets-Sheet 4 I. I III/denier HERBERT L.BAILE j MflOrmQV" H. L BAILEY METHOD AND MACHINE FOR FILE GRINDING Filed March 14 Sept. 3@, 1930.

Sept. 30, 1930.

H. L. BAILEY METHOD AND MACHINE FOR FILE GRINDING Filed March 14 1925 7 Sheets-Sheet 5 \lllJ llllllll G 5 w M6 i .7 1 wwfiw 7 5 5 w m 9 .V.. wwM ;fi /2,22 wm z... .2222%,,25,2 .r i... n M a 4% 5 I 5 G B G a m m B m H Inventor- HERBERT L. BAILEY Sept. 30, 1930.

H. LuBAlLEY METHOD AND MACHINE FOR FILE GRINDING Filed March 14, 1925 7 Sheets-Sheet 6 FIG 7 Sheets-Sheet H. L. BAILEY METHOD AND MACHINE FOR FILE GRINDING Filed March 14 FIG. 22

5ept. 30, 1930.

ATTORNEY.

R. 0 Y T 7 WA 5 L T R E 5 R E H FIG. 24

I/MIIIII'IIIII e I FIG. 25

Patented Sept. 30, 1930 PATENT OFFICE HERBERT L. BAILEY, OF PHILADELPHIA, PENNSYLVANIA METHOD AND MACHINE FOR FILE GRINDING Application filed March 14, 1925. Serial No. 15,592.

My invention relates to file grinding machines. The machine which I have designed is especially adapted for the grinding of files, the teeth of which are machine-cut and 5 are of a substantial and uniform distance apart. Such files are known as cutting files rather than abrading files inasmuch as the teeth are sharpened in such fashion that each'one of them shaves or cuts the surface of the metal in a regular manner as distinguished from the irregular scratching and abrading action of the ordinary file. These files are commonly made by special milling processes and are very expensive. By my invention I am enabled to sharpen the edges of these teeth when'they are dulled a number of different times whereby the life of the file is greatly prolonged, and the great expense of new files hitherto incident to the dulling of the teeth is eliminated. These tools can now be used with great economy.

.The general object of my invention is the production of a machine which will effectually sharpen these cutting files. Ef-

fectual sharpening requires not only that the edge be shar but also two other important things. irst, that the cutting angle of the edge be correct, otherwise the file will not take hold upon the work, and, secondly, that the cutting edges of all the teeth of a given file lie in the same eometric plane, or in the same geometric sur ace upon which they were originally designed to lie. Otherwise the teeth will cut unequally and the file will soon be dulled in spots and become quite useless.

My object is principally to produce such a machine which will grind these files automatically without any special attention on the part of an operator once the initial adjustment for the first file to be ground has been made, and once any file has been inserted into a machine so adjusted. This requires not only automatic but very 1ntimate relation between grinding tool, workholding and work-feeding mechanisms.

It is a further principal object of my inventionto provide for the ready adjustment of the machine as a Whole and all its automatic features to accommodate not only files of different sizes and spacings of teeth, but also files of different makes and types, and general variation in configuration. Such adjustments are necessarily multiple in character and of both a major and minor nature, and effect in common the grinding, work-holding and feeding mechanisms.

In a kindred line I aim also to provide those exacting adjustments which enable me to accomplish in connection with these various kinds of files that same effectual grinding which I have outlined above as the primary object of my invention, to repeat.a

sharp edge on each tooth, a proper angle to each face, and a proper alignment of the edges of all the teeth in the geometrical surface which they should occupy. Beyond this I aim to make the adjustments such that there shall be provided on each tooth a let off at each end sulficient to prevent scratching which might accompany the presence of asharp corner or point. For it must be remembered that the particular work of exterior finishing upon which files of this class aroused will not admit of scratches in the surface of the body being finished.

In accomplishing my aims I have invented an entirely new method of grinding, a method involving a considerable number of steps. To begin with, I establish the oint of greatest depth of the grinding to t e rear of the tooth edge and traverse this point of greatest depth on a path parallel to the tooth edge. This insures uniform edge on the tooth and long life to the work. Another step involves the holding of the work to the grinding tool by yielding pressure insufficient to hold the Work in its initial position. This adds to the preceding advantages the advantage of a let- Qfi' at each end of each tooth whereby the 0bjectionable sharp corners aforementioned are eliminated. Yet another step comprises the relative movement of the work and the grinding tool on a zig-zag path taking in alternate teeth on corresponding branches of the path, whereby there results further uniformity of cutting edge, adherence to cutting surface, and lllgll speed of operation. A still further step is the gravitational balance of the work during the grinding operation, whereby the displacement of the work, due to unwonted grav tational components, which may vary as the work is belng fedfrom one position to another, is entirely obviated. An ancilliary step is the application of all holding and feeding forces symmetrically with reimproved means for feeding the work so held,

and likewise improved means foradjusting the work and the grinding tool, and the Various parts having to do with them, all in such fashion as best to practice the method which I have evolved.

In the accompanying drawings, I have shown that embodiment of my invention now best known to me.

' Of these drawings,

Fig. 1 is a general sideelevation of the entire machine.

Fig. 1--A is a similar side elevation of the entire machine from the side opposite that of Fig. 1. i

Fig. 2 a substantially longitudinal central vertical section. It resembles Fig. 1 except for the sectional showings and the omission of a driving motor. I

Fig. 3 is a top plan view of the machine.

Fig. 4-is a transverse section on the zigzag line 44 of Fig. 2. a

Fig. 5 is an end elevation of the workholding end of the machine.

Figs. 6 and 7 are, respectively, plan views partiallyin section of the friction clamp of the work-holding means.

Figs. 8 and 9 are, respectively, front elevations of two different forms of this clamp.

Fig.1'0 is a section on the line 101O of Fig. 2 showing salient elements of the workfeeding mechanism.

Fig. 11 is a semi-diagrammatic view showing other salient features of the mechanism and method of feeding.

Fig. 12 is aview of the portion of the drive of the feeding and grinding mechanisms taken substantially on line 12-12 of Fig. 3 looking in the direction of the arrows and showing in full lines parts shown in dotted lines in Fig. 1. i

Fig. 13 is an elevation partially in section of one form of operating mechanism for the grinding tool, the sectional portion of the figure being taken substantially on line 1313 of Fig. 3.

Fig. 14 is a plan view of this mechanism with certain of the driving elements opened apart.

Fig. 15 is a side elevation of a modified form of grinding tool'operating mechanism.

Figs. 16 to 21 are diagrammatic views having to do with the explanation of the method of my invention.

Fig. 22 is'a section showin certain gearing of the driving mechanism taEen substantially on line 22-22 of Fig. 1.

Fig. 23 is an enlargement of a micrometer adj ustment shown in Figure Fig. 24 is a vertical section of the fore end In the machine I have developed to carry.

out the method of my invention, the main driving mechanism for the whole,the grinding tool operating mechanism, the work-holding mechanism, the work-feeding mechanism, and the adjusting mechanisms have been coordinated and combined together into a highly efiicient whole. In the drawings, the main driving mechanism is by the letter. D, themech'anism for operating the grinding tool is desi 'nated by t e letter G, the work-holding mechanism by the letter H, the work-feeding mechanism by the letter F applied to its salient elements, and the adjusting mechanism at large by the letter A. Coordination of the work-holding, feeding and adjusting mechanisms brings them into a simplified unitary group structure as clearly 1 appears in Figs. 1 and 4, exce t that related portions of the feeding and ad usting mechanisms are embodied in the same structure with the main driving mechanism D, as indicated by corresponding group designating letters in the bod of group D. The whole is supported rom a pedestal P which stands upon an extended horizontal base S.

The base S comprises the main body 30 of considerable width and a relatively narrower portion 31 upon which the pedestal P is mounted. The pedestal itself is provided with a head 32 lying in a substanially horizontal plane. Swiveled to it by a central securing bolt 33 by means. of which-it may be clam ed and unclamped to the head, and angular y adjusted upon the'head, is a stirrup 34, u on which the main drive casing 35 of the driving mechanism D is supported from the pedestal. The stirrup 34 is preferably integrally formed with and depends from the bottom of the fore end of this casing 35. The casing 35 is box-like in form,

as clearly appears from Fig. 2, a view in. which its interior is shown by removing its front side 36. The side 36 is purposely made removable for the urpose of rendering accessible the parts 0 the main driving mechadesignated generally lo'u lzio

nism enclosed within the casing. The side 36 is provided with hinges 37 at its rear end permitting it to swing outwardly, but it is normally secured in place by securing bolts,

38, applied to the corners or to other con venient points. The lubrication and protection of the parts of the driving mechanism within the casing, 35, are properly assured by its normal closure. From the rear end of the motor casing depends the bracket or spider, 39, to which the driving motor, 40. is attached in-a vertical position by means of any appropriate securing 'means. This driving motor has a vertically-extending main driving shaft, 41, from which all of the mechanisms of the machine requiring power to drive them are driven. The vertical shaft,

41, is appropriately journaled in upper and I means of a bracket structure 44. From the lateral branches of the stirrup 34 the workholding, feeding and adjusting mechanisms H, F, and A, are supported largely in position laterally of the grinding mechanism G.

- This support is by means ofa laterally projecting arm socketed in a lateral extension 46 from the front branch ofstirrup 34, and a vertically-extending column 47 mounted pivotally thereon, as indicated generally at The elements of the driving mechanism per se other than the driving motor 40 and its drive shaft 41 will be best comprehended as described in connection with the particular ones of the other mechanism with which suitable type, such as is well known in the art, by means of an upwardly-extended shaft 51 upon which it is mounted. A pulley 52 on the shaft 51 is driven by a belt 53 which I connects it to a driving pulley 54 on theupper end of the main drive shaft 41 so the grinding tool is rotated at.the high speed required. A belt-tightening idler 55 carried at the upper end of depending crank arm 56 is mounted for vertical and angular adjustment in an oscillatable and adjustable pedestal 57, and spring-pressed to the belt 53 by the spiral spring 58 having one end bearing on the casing 35 and the other end engaging the pedestal 57.

Grinding wheel 49 of the mechanism G is supported in an inclined transverse plane, as clearly appears in Figs. 1 and 2, by means of an arm 59 associated with the bracket 44 by which the mechanism at large issupported. Arm 59 carries the grinding tool by meansof a split collar 60 adj ustably clamped around the bearing 50 of the grinding tool by means of screw 61 (see Fig. 13), whereby the grinding tool may be freely adjusted vertically merely by loosening clamping member 60 and moving the bearing longitudinally therethrough. But the arm 59 is not fixedly connected to the bracket 44. It is mounted (see Figs. 13 and 14 particularly) on a sliding head 62 carried upon a transverse shaft 63. This shaft 63in turn is supported in depending cars 64 in a grinding mechanism supporting frame 65 carried from the bracket 44 on the upper side of the casing 35. Support is by means of a tubular boss 66 telescoped over the tubular forwardly and substantially horizontally extending end 67 of bracket 44. It is adjustably held in this relation by means of set screw 68, through the release of which it may be moved angularly about the axis of extension 67 and reset in a different angular position whereby the obliquity of the plane in which grinding tool 49 operates may be set to any desired angle.

- Immediately overlying the transverse shaft 63, the head 62. is provided with a rack 69. This rack is engagedby a pinion 70 on the'end of a shaft 71 journaled interiorly of bracket 44 and its with the" tubular extension 67. The opposite end of shaft 71 projects rearwardly free of bracket 44 (Figs. 1 to 3) and is there provided with beveled gear 72 meshing with a like gear 73 on the upper end of a shaft 74 boss 66 and co-axially extending substantially vertically down through the top of casing 35. On its lower end this shaft 74 is provided with a second beveledgear 75 which in turn meshes with the segmental beveled gear 7 6 carried by a horizontally extending stub shaft 77 secured to the cover plate 36 of the casing 35. This segmental gear 76 (see Figs. 1 and 12) is provided with a rocking arm 78 having a pin and slot connection 79 of an adjustable nature with the rocking link 80 connected in turn at its opposite end adjustably with the side of a rotatable cam 81 mounted on a second stub shaft 82, also secured on the cover or door 36 ofthe casing 35. This cam 81 is in turn coupled with a worm gear 83 (see Figs. 1 and 22) having, a driving engagement with the vertically-extending worm 84 carried by the vertically-extending driving shaft 85 journaled in the top and bottom walls of the casing 35 intermediate the side walls thereof. This shaft is driven by belt 86 from the main drive shaft 41, the speed D grindin mechanism G is operated and grinding w eel 49 reciprocated laterally in a determinate path,

The work-holding mechanism H comprises, in the main, a friction clamp 89 adapted to frictionally hold the work, as for example the file 90, in position before the grinding tool 49. This friction clamp, when the Fparts are in operating position, as shown in igure 2, supports the work in a substantially verticai position, asclose to the vertical as posible, so that the work is gravitationally balanced about an axial line, such as 91. The clamp is supported from an inwardly extending arm 92 connected with the upper end of column 47 which in turn, it will be remembered, is supported by the horizontally extending arm 45 socketed in stirmp 34. The clamp comprises a head plate 93 carried upon the headed ends 94 of bolts 95 projected, respectively, through the tubular ends 96 of a bracket 97, centrally mounted upon a circular shaft 98 carried in the upper end of the forwardly-extended arm 92. Shaft '98 is adjustably carried on arm 92 by virtue of its passa e through the complemental bearing member 99, and its retension therein in adjusted position by means of the winged adjusting screw 100. Similarly, bracket 97 is supported upon shaft 98 by a complemental bearing 101 and held in 'its adjusted position by a winged adjusting nut 102, and the head 93 is retained upon the bracket by wing nuts 103 on the ends of the bolts 95.

This head 93 of the friction clamp is provided with a pair of front jaws 104 of angle form in transverse section having branches 105 which roject toward each other in spaced relation to the head 93 and other branches which extend toward the head 93 and are secured to complemental branches of angle slides 106. These slides are slotted, as at 107 (see Figs. 8 and 9) and are retained in place by the heads 94 of the clamp head securing bolts 95, the bodies of which are passed through the slots. Moreover, the clamp head 93 is provided with slots 107 Fig. 5-in registry with the slots in the members106, and members 106, at their inner edges, are provided with lugs 108 which pro- Lect into the slots in the clamp head 93 where- -y swinging movement of members 106 about the bolts 95 is precluded, and the jaws 104 are maintained in their vertically aligned position. Yet the provision of

slots

107 and 107 permits of a considerable range of lateral adjustment of the head plate 93 bodily, and of the clamping jlaws 104 in particular, merely by loosening of the wing nuts 103 which free the parts from the binding action of hqeads 94, which secure them to the bracket 9 The jaws 104 are adapted to' engage the front face of the work by the overhanging 109, may be easily removed for the renewal of the surfaces or the replacement of the jaws by others. The work is borne to these work-engaged interior faces 109 by means ofa rear clampin jaw 111 in the form of a head projected t rough an aperture 112 in the clamping head 93 from the rear by a spring-pressed plunger 113. This plunger is mounted withm the hollow 114 of the shaft 98 which supports the friction clamp 94 itself. The shaft 98 is formedas a tubular barrel having its end adjacent the head plate 93 closed and its opposite end open. Plunger 113 is in the form of a rod projected through anopening in the closed end of the shaft 98, provided adjacent thereto with a fixed collar 115 and, surrounding its body, with a spiral spring 116, borne upon the collar by a tubular adjusting plug 117 threaded into the opposite end of shaft 98, and through the hollow of which, in turn, the end of the plunger 113 is extended and provided with a hook 118 by means of which it may be manually operated. The spring 116, through its engage-' ment with shoulder 115, holds the clamping jaw 111, carried at the fore end of the plunger, against the rear face of the work and presses it firmly against the interior faces of the jaws 104. This clamping jaw 111, like the wearing surfaces, 109 of the friction clamp (see Figs. 6 and 7), ma be made of any suitable wearing material st'suited to the holding of the work without abrading it or marring its sharpened teeth. It also is removable from the lunger, being threaded or otherwise remova 1y held on its fore end whereby, it, too, may be renewed upon wearing down.

The feeding mechanism F, by means of which the work so held before the grinding tool is moved relatively thereto, comprises, as its salient elements, a feeding pawl 119 carried at the end of a feeding arm 120 on the front face of the work below the grindin tool and intermediate the grinding tool anthe horizontally-extending arm 45, which supports the holding and feeding mechanisms. This feeding pawl 119 is of bifurcated form, appearing most clearly in .the semi-diagrammatic view in Fi 11. It is comprised of a strip or rod or wire bent into substantially U-form. The bend 121' of the U is held beneath the head 121 of a clamping bolt 122, secured in a supporting bracket 123 by means of wing nut 124. The upper ends of the branches 125 of the nawl 119 are flared outwardly, and are curved toward the work as clearly appears in Figs. 1 and 2, and their points are not only beveled on their upper surfaces, as indicated at 126, in Fig. 11, to sharpen their engaging ends, but these engaging ends themselves are cut transversely to conform to the shape of the teeth of the work, as indicated at 127 in Fig. 11, in which the teeth are curved. In the casekof straight teeth, as illustrated in the diagram in Fig. 16, these ends would appropriately be straight.

Bracket 123 is freely journaled upon a tubular ferrule 128 having a head 129 on one side and projecting a distance beyond head 123 at the opposite side. The ferrule 128 is force-fitted onto the feeding arm 120'so that it is normally immovable with respect thereto. Force-fitted on the extended end of the ferrule is an adjustable tension head 130, adjustable by the application of force only against. its friction hold upon the ferrule. The inner end of this head is hollowed out and within it is mounted a spiral tension spring 131, one end of Which is engaged in the head 130 and the other end of which is engaged in the bracket 121, whereby the feeding pawl 119 is borne yieldingly to the face of the work and the tension under which it is borne may be freely adjusted.

' The feeding arm 120 is L-shaped,the branch which supports the feeding pawl 119 projecting laterall below the grinding tool 49 from the right 0 the machine. The main branch 132 of the arm (see Figs. 2 and 10) is rotatable and axially supported for adjustment in a boss 133 in a'bracket. 134 (see Fig. 5) 0f U-shape journaled by its arm on a transverse axis 135 (see also Fig. 5) supported there by 7 the forward extensions 92 of the column 47. The branch 132 of the feeding arm is supported substantially from a corner of the U-shaped bracket. The bight portion of the bracket underlies the extension 92 and is provided centrally with a depending tang 136 in which there is threaded a designated stop. screw 137 provided with a wing jam nut 138.

The'point 'of screw 137 bears against the front ,wall of column 47 and, in accordance with its adjustment, limits the upward stroke of the feeding pawl (see Fig. 2). Bearing upon the central portion of the bight of the U-bracket 134 from the front is a plun er 1-39 yieldingly pressed into engagement y the spiral spring140 housed in abarrel 141 formed on the under sideof the extension 92,'and provided with a tension adjusting screw 142. Through the plunger 139, the feeding pawl1l9 is carried through its feeding stroke by the potential energy stored in spring 140 by the driving mechanism.

The driving mechanism is connected with the bracket 134 by means of anvarm 143 depending from the bracket on the same side of the machine asthe feeding-arm 132. This arm is provided with a socket 144 on its'lower end offset laterally of itsmain body, and rethe under side of a small bracket 147. In

the upper side of bracket 147 at right angles to the lateral side of arm 145'is an elongated a pin 148 having a knurled head 149 at its forward end and a shank 150 at its rear end,

force fitted into the tubular section 151 of a connecting

rod

151, 152, extending lengthwise of the machine. Section 151 is screw threaded upon the fore end of section 152 so that by turning the knurled head 149 of pin 148, the aggregate length of connecting

rod

151, 152 may be readily adjusted. At its rear end, (Figs. 1, 2, 3 and 4) this connecting rod is turned inwardly of the machine b a branch 153 and, underlies the casing 35 of t e driving mechanism D. Emerging on the opposite side of the machine, branch 153 is reversely turned as at 154 and its inturned end 155 detachably socketed in the lower end 156 of an oscillating lever 157 carried by a rock shaft 158 journaled through the. upper margin of the cover plate 36. On its inner end, this rock shaft 158 is provided with a depending cam lever 159 carrying on its lower end cam follower 160 in a position to be engaged bycam 161 mounted upon transverse shaft 82 Thereby through the reciprocation of the con identified with the driving mechanism of the

necting rod

151, 152, and the resultant feeding of pawl 119, there are obtained two feeding strokes for each angular grinding stroke of the grinding tool 49. c i V The adjusting mechanism A is comprised in considerable part of elements which have;

already figured in connection with the holdsupport of those mechanisms. Column 47 is capable of a number of adjustments with respect to the forwardly extending arm 45 upon the far end of which it is carried. It has already been said that it is pivotally mounted on axis 48 at the outer end of this arm. This pivotal axis is mounted across the bight 162 of the hook 163 of arm 45. The body of the hook, 163, lies on the same side of the machine as the main branch 132 of the feedin

mechanism supporting arm

132, 120.' Both the'hook 163 and the feeding mechanism arm 132 are open on the opposite side of the machine (see Figs. 2, 4 and 10) whereby work may be inserted into and removed from the machine freely from that side without havmg and feeding mechanism, especially in the ing to thread it vertically through the body of either element. Furthermore,,work may on occasion, depending upon its shape, be the more readily accommodated.

Column 47 is supported from axis 48 by a bracket 164 in which it is axially disposed, and held in its adjusted position by means of a lever operated screw 165. This bracket is provided-with a forwardly extending lug. 166 which underlies the bight 162 of hook 163 in such manner that the bightconstitutes a stop limiting the extreme rearward movement of the column 47 about its pivotal axis 48 toward the grinding tool 49. Extending vertically through lug 166 within the bight is a spring pressed L-shaped plunger 167, the horizontal branch of which engages bight 162 on its upper side, whereby column 47, and consequently the work holder 110, are yieldingly held in the normal position relative to grinding tool 49 imposedby the engagement of stop 166 with an under side of the bight. A knurled nut 168 provides adjustment for the spring 168'. thereby regulating the force with which the work is presented to the grinding wheel.

Pinned or otherwise secured to the column 47 just above the top of the supporting bracket is a. thrust collar 169. This collar is provided with right and left wings 170 in which are mounted set screws 171 which engage opposite sides of a vertical lug 172 from the bracket 164. So when the lever screw 165 (Figs. 1 and 5) is loosened, bydetting off one set screw 171 and turning up the oposite one, column 47 may be angularly adjusted about its axis and held fixedly in such adjusted position. By loosening set screw 173 which holds collar 169 upon the column 47 and also loosening lever screw 165, the col umn may be vertically adjusted. By rotating the L-shaped plunger 167 so that its overlylng branch is removed from the bight 162 of the supporting arm, the entire holding,

feeding and adjusting mechanisms thus far described can be dropped forwardly away from grinding tool 49as shown in Fig. 1.

The supporting arm 45 is itself adjustable forward and backward within the offset 46 by means of which it is supported from stirrup 34 (see Figs/2, 4 and 23, especially Fig. 2). It is not only journaled in this boss for both axial and an ular adjustment and held normally clampe therein by a lever screw 174, but also provided at its rear end with a micrometer adjustment comprising a small pitch screw rod 176 threaded into therear end of arm 45 and provided with a knurled head 175 journaled in the opposite branch of stirrup 34 from the carrying boss 46. Collar 177 prevents movement of the micrometer screw with respect to the arm of the structure so that when the knurled head 175 supporting arm 45 is adjusted is turned, lever screw 174 beingreleased, the y micrometer movement forward or backward as may be desired. During such adjustment it is normally prevented from angular movement which might turn the mechanism which it supports up side down, by means of a head 178 clamped to its inner end within the body of the stirrup 34 and having a pair of depending'ea'rs 179, one disposed on each side of the head of the pedestal, and each ear provided with an adjusting screw 180, all as shown in Figures 1, 2, 4 and 25.

This machine greatly facilitates the practice of my invention. very easy to practice. The file or other similar tool to be ground) is inserted into the friction work-holding clamp 89 of the workholding mechanism H with its teeth pointing downward as clearly shown in Figs. 1 and 2. It is easy to insert it, for one has merely to grasp the hook 118 and pull the rear clamping jaw 111 away from the fore jaws 104 ..(Fig. 3) and insert the upper end of the file between the 'jaws from the bottom. Thereupon when the hook 118 is released, jaw 111 bears frictionally on the back of the work and holds it against the faces 109 of In fact it makes it the fore jaws 104. In this insertion of the I work there has been no interference from supporting arms 45 or from the arm 120 of the feeding mechanism F, since the one is hook shaped as in 163 Fig. 4) and the other is L-shaped, both open on the left hand side of the machine. So inserted the file is held by the frictional engagement of the jaws '164, 111, with the edges of the teethon its front andback. The teeth. of course, during this insertion ratchet freely past the upper end of the feeding pawl 119 of the mechanism F. Initially. of course, the work is hardly more than entered by its upper end in the work-holding clamp 89 when the first several teeth are engaged. Thereby the ins grinding tool 49 may commence its work almost if not quite at the extreme end of the file. In cases where this extreme end is blank,

it is the blankend which is held by the aws 104, .111, and the grinding operation maycommenceupon the very first tooth, there machine after this insertion of the work takes place as follows: The driving motor 40 bein' started. g'rindin tool 49 is rotating at big s eed through t e belt connection 53, and is a so, at the same time, reciprocated transversely of the machine. This 1s accomplished through the train ofinechanism including rack and pinions 69 and 70 and comprehending parts 1 to 88 of the grinding mechanism G and the' drivin mechanism D as most clearly appears in .igs. 1, 2, 12 and 13.. At

the 'same'time the feeding mechanism F is operated at a coordinated periodicity by means of the train of mechanism commencing with oscillating feeding arm 120' which carries thev feeding pawl 119 extending through the connecting rod 151 and ending with lever 159 and cam follower 160 (Fig. 12) actuated by cam 161 driven from the same shaft 82 from which is driven the mechanism for reciprocating driving tool 49 just recited. For every revolution of shaft 82 grinding tool 49 is reciprocated once, by reason of the fact that'connecting rod 80 (see Fig. 12 and Fig. 1) oscillates segmental gear 76 of the train once for each revolution of shaft 82.

But for each revolution of shaft 82 cam lever 159 is oscillate-d twice by reason of its engagement, once by one end of the double ended cam 161 of lozenge shape, and once by the other end during each revolution. And these engagements'are precisely 180 degrees apart. So feeding pawl 119 of feeding mechanism F makes two feeding reciprocations to one feed ing reciprocation of grinding tool 49. The time is so adjusted that feeding takes place at or near the extreme end of each stroke of the grinding wheel, while the wheel is out of engagement with the work, with the result that the grinding tool 49 engages every other tooth on its strokes toward one side of the machine and thealternate teeth on its strokes to the opposite side of the machine, passing in its grinding operation over each tooth during a single insertion of the work in the machine. The relative path of movement of work and the grinding tool is therefore substantially a zig zag path.

The nature of the engagement of the grinding 'tool' with the work will. be clearly apparent from a-consideration of Figs. 16 to 20. In Fig. 19 is shown a length of file the teeth of which have not been ground In Fig. 20 is shown a length of teeth'of which have been ground. It will be seen that the grinding operation is carried out on the margins adjacent the edges of the teeth as indicated by numeral 181 applied to these marginal portions, and that the grinding does not extend all the way to the roots of the teeth. F urthermore this margin is on the tops or outer faces 182 of the teeth and not upon the bottoms or inner faces 183. The teeth on most if not all straight tooth files are formed traversely oblique to the sides of the file as clearly appears in Fig. 16 which represents the same length of file as is shown in Figs. 19 and 20 in front elevation, the teeth pointing downward as in position in the machine. Here the grinding tool 49 is shown in dotted lines and its axis of rotation is shown by a dash and dot line 184. The central lane 185 of the grindin tool is intersected by the axis 184 at a po1nt'186 which lies a substantial distance behind the cutting edge 187 of each tooth upon the oblique outer surface. 182. The

grinding tool 49 is so disposed to the vertically extending work holder 89 and the ver tieally disposed work 90 as to maintain this relation to the parts. Furthermore the angularity of the transverse-shaft 63 '(Figs. 1 and 13) is so adjusted by means of movement of frame 65 about support 44 of the grinding mechanism as to insure apath of travel of the grinding tool 49 and of its central contact with the work as defined by the point 186 projected upon the plane of the work, substantially parallel to the edge of the tooth throughout both strokes of each reciproca- 1 tion of the grinding tool 49.

So those steps of the method of my invention involving grinding to the greatest depth at a point to the rear of the tooth edge and traversing the point of greatest depth parallel to the tooth edge are carried out. This will be additionally apparent from the inspection of Fig. 21 showing the work and a section of the grinding tool 49 in side elevation. Here projected point 186 lies a substantial distance back of the cutting edge 187 of the tooth being ground andthe grinding tool is rotated to grind toward the edge of the tooth.

It will be apparent too that the plane of the grinding tool 49 lies at an angle to the cutting edge 187 of the tooth, and the line of grinding contact, and at an acute angle a Fig. 16 disposed at an opposite inclination to the body of the work from that of the tooth edge 187, or in the direction of said opposite inclination. By such disposi tion the general inclination of the plane 185 of grinding tool 49 is maintained at a much less value than if the grinding tool 49 were inclined in a same general direction as the tooth edges 187 with a resultant closer approach to symmetry and smoothnessof op eration of the grinding mechanism. Through these and the former arrangements is carried out that step of my invention involving grinding in the path at an angle to the tooth edge, the while traversing the grinding parallel to the tooth edge. Through it too iscarried out that step involving the establishment of the greatest depth of cut in the rear of the tooth edge and carrying out the same traversing movement, and the grinding on an are shaped path at an angle to the tooth edge and tangent the tooth edge, the curvature of grinding tool 49 itself establishing the are shaped path and the disposition of the grinding tool described establishing its tangency to that line defined by the traverse of the projected point 186.

During these operations the tension of the spring 168', by means of which the column 47 and consequentlythe work holding and feeding mechanisms F and H are retained in vertical position, is adjusted to such value full engagement, as it is when it engages between the ends of the teeth, forces the work and consequently the work holding and feeding mechanisms F and H ever so slightly back from the adjusted normal position as defined by the engagement of the lug 166 j (Fig. 2) withthe under side of the-hook 163 of the arm 45. But this movement through compression of spring168 is' made so slight that there remains that depth of cut which may be desired for each stroke of the grinding tool." To put it another way-assume the i spring 168 is adjusted to that value which. will, when the grinding tool 49 is in full engagement," result in that depth of cut desired for each stroke and also in a slight yielding movement of thework before the grinding tool. Theresult is the formation at each end of each tooth of a let-off 188, due to the fact thattlie pressure of spring 168' when the grinding tool is entering its engagement 7, with the tooth and before the tooth is fully in engagement therewith is sufficient to quite overcome the less grihding pressure incident to such lesser engagement than the fuiler en- .gagement' and thereby to cause the grinding tool toe ect a deeper cut at the extremities ofthe teeth than it does at points intermediate to the points on the extremities, and to progressively decrease this depth of cut to the normal as the full engagement is reached. 5

This let-off effectually precludes the extension of undesirable sharp .points at thBBX- tre'rne endsf of the tooth and eliminates the Scratchings caused by each sharp points.

The'presentation of the work to the grinding tool in a position which, if not changed, will result in a depth of cut greater than desired,

,. and holding the work to the grinding tool under yielding pressure insufficient to maintain its position before the tool when the tool is fully in engagement, and thereby .to form :teeth with a let-off at each end is a part of my method. a During these operations the work 90 is, of

course frictionally held in the work clamp H, an jointly by reason of the general vertical position of this elamp, its frictional nature and the engagement of the teeth in the feeding operation by the ends 127 of the feeding pawl which are disposed on the angle to the true vertical that the tooth edges bear. to the central axis of the file (see Fig. 11), the work is fed vertically .upwardialways in gravitational balance about its true vertical axis. More' broadly stated, the ends 127 of the feeding pawl 119 are disposed on a line 1 bearing the same relation to'the true vertical as does the line of the tooth edge to the longitudinal axis of the work. The work holdto ing clamp being of africtional nature and 'there being sufiicient play between its sidel walls b reason of the provision of a spring 105 igs.6 and 8) to preclude a guiding action b any other than the desired one of 66- these si e walls, 105", the feeding operation itself maintains the gravitational balance. Thereby I am enabled to practice those steps of my mvention involving the maintenance of this gravitational balance of the work in a vertical position to the grinding tool and to obviate entirely" all variations whatever or defects of rinding which might result from'the introduction of any angular gravitational components. Such eomponents with the work fed in any other manner vary with each movement of the tool through its hold er, become reversed in sign as the work progresses, and introduce such variations between the individual teeth as to preclude that accuracy essential in files of this kind.

Moreover, in furtherance of this result I have constructed my apparatus, it will be perceived, to enable meito apply a holding pressure through the clamping jaws 111 and 104* symmetrically distributed with respect to the longitudinally vertical plane. This will be clearly apparent from an inspection of Figs. 3 and 5, in which this plane has been designated by the

lines

91 and 189. There is thus no tendencypf the clamping pressure, as adjusted to most effectually coact with the feeding pawl 119 by turning up the adjusting-screw 117, to interfere with the balancing actionof this feeding pawl as the work is moved step by step forwardly. Moreover, the feeding forces themselyes, by my apparatus, are symmetrically applied as respects this longitudinal vertical planev 189 by reason of the symmetrical disposition of the arms 125 of the feeding pawl and their engagingpoints 127 as respects this plane. (See Fig. 11).. This step of my method renders more'efi ectua l practice of that step involving the; feeding of the work in gravitational balance. I g

Of like assistance is that feature enabling me to frictionally. hold thework before the grinding tool. But this feature is of still further advantage in that it enables me to hold work having teeth of different pitch *and size without carrying out adjustments of the work holder itself. As an example, under certain conditions, unless the variation from the pitch in one piece of work is more than twice the pitch of the original, no resetting of the feeding mechanism F is necessary. For when the feeding mechanism is set for a stroke substantially greater than the distance between two. successive teeth, and stop 137 is adjusted to present the edge of the tooth being ground in proper relation to the path of traverse of the projected point 186, (see' Figs. 16 and 2 1); no matter what the length of the tooth within setting of the feedingmechanism F, the tooth edge is always presented in this same relation to the path of travel of the projected point 186. This follows because, while the feeding pawl is moved on 1ts.down stroke positively, it' is moved on its up stroke by potential energy, energy Q ting of stop 137 on theforward stroke.

stored in spring 140 on the back strokeand utilized to the extent determined by the set- So this step of holding the work frictionally in a determined area, conducting the grinding always in the central region of this area, and

progressively shifting the clamped area from one extremity of the work to the other, and the feeding of the work through potential energ enables me to maintain accurately the relation to the grinding tool and the tooth edges and to still further increase the fineness of the work turned out.

When a piece of work is finished it is supported in the clamp 89 of the work-holding mechanism H at its extreme lower end. In this position, feedihg pawl 119 having engaged the lowermost tooth, further feeding movement is impossible, and grinding tool 49, unless the work is immediately removed, may engage and reengage-the next to the last tooth (since pawl 119 works within one or two teeth ofthe plane of the grinding tool) and grinds this tooth to a slightly greater depth than the remaining teeth. But this is not harmful for two reasons, first, because the very limit of depth as fixed by the engagement of lug 166 with thehook 163 (see Fig. 2)' of arm is not very great, being only sufficiently greater than the body depth of grinding to insure a slight let-0E at the ends of the tooth, so that full depth of grinding will not be excessive. Furthermore, the sound of the machine is changed the moment grinding to a different depth occurs, and the operator may promptly change the work.

lil)

Work is ground on one side and then tested on that side by application to a surface to be filed, and if insufficiently sharp by reason of being inordinately dull, or for any other cause, the work is re-entered by its upper end in the work holder and the same face given a second grinding, or indeed a third if that should prove necessary. The work is then reversed and the opposite side ground.

I The adjusting mechanisms provided not only assist me in the practice of the method of my invention, but also serve variousother ends. The micrometer

adjustment comprising elements

175, 176 etc., enables me very accurately. to adjust the maximum depth of cut merely by turning the knurled head 175. This produces most accurately those'minor movements of the work-holding mechanism H necessary for such accurate adjustment. hen the work has been finished, however, the adjustment effected through a release of the L-shaped plunger 167, through a rotation of the plunger 167, bythe knurled unit or thumb piece 168, enables me to drop the entire work-holding mechanism H forward from the position shown in Fig. 2 to that shown in Fig. 1, whereby not only may the work be inserted and removed without interference from grinding tool 49, but also any ficaciously effected through the adjustment 7 providing angular adjustment of column 47 about its axis by means of the opposed set screws 171 in the bracket 164 which supports the column on its pivot 48. Lever screw 165 being released, one has only to let off slightly on one screw 171 and take up-the same amount on the other, whereupon angular adjustment is fixed. That is a most important provision in that it is one of the factors insuring absolutely uniform depth of grinding throughout the length of the tooth. At any time,

the column 47 may also be adjusted axially,

but this adjustment. is mainly for general positioning of the work-holding mechanism.

H with respect to the plane of the grinding tool such, for example, as to insure the enrespect to the path of travel of the projected 1 point 186 (Figs. 16 and 21) is effected by adjustment of the stopscrew 137 associated with the feeding mechanism F. The feedingmechanism F possesses several other adjust ments, but no others which are directed to this especial end. The adjustment provided by wing nut 124 is to enable the pawl 119 to be shifted laterally one way or the other, and enable the symmetrical application of feeding force with respect to the longitudinal vertical planeto be maintained irrespective of the kindof work or of the relative location of the grinding and work-holding mechanisms. A further adjustment is provided in the variable length of the depending

arms

143, 145. This provides principally that adjustment required by vertical adjustment of column 47 Subordinately, however, it may be used to vary the length of the stroke of the feeding pawl, and also is a convenient means of knock down and assembly 1n case the 'samelength of feeding'stroke on aw 111 irrespective of the location of the work-holder longitudinally of the machine.

This location is changed from'timeto time for the slmple reason that as the grinding wheel wears, "thef-

micrometer

175, 176 is adjusted nately, however, this connecting rod adjust- .

ment

151, 152, does enable me to control the length of stroke of feeding pawl 111 by reason of the fact that operating connection from cam 161 to cam follower 160 is a lost motion connection, and

whenrod

151, 152 is lengthened or shortened, the amount of lost motion is reduced or increased with a resulting increase or decrease in the effective stroke of the pawl 111. By this means, therefore, I am enabled to adjust the length of stroke to work having. teeth of different pitch, as I will.

. Finally, the'innerend of

thls connection

151, 152, being removably carried in the end 156 of lever 157, (see Fig. 1), I am able, by simply iwithdrawing it, to free the cover plate 36 and enable it to be thrown open to disclose the interior driving mechanisms for inspection and to general accessibility to them.

The adjustments of the work-holding mechanism H are utilized principally in chan ing from one kind of work to another. ere, when a batch of new v work of different size is to be operated upon, first the work-holding mechanism is dropped back as shown at Fig. 1, wing nuts 103 are loosened, and the fore jaws 104 are adjusted approximately to the width of the inserted work, so that one side bears against and is guided by the side wall 105-13 of'one jaw 104. The other side is borne upon yieldingly by the spring 105a. Then wing nuts 103 are tightened up. Loosenin thumb screw 102,- the work holder 89 is a justed bodily upon the shaft 98 until the pressure exerted by the back jaw 93 is adjudged to give that (approximately) degree of friction clamping desired. Thereupon the column 47 is swung to its vertical position, as shown in Fig. 2, and in this position thethumb screw 100 is loosened and the work holder 89 adjusted toward or from the tion of shaft 98 in boss 99. And when in pobe attained.

sition, the single thumbscrew 100 retains the parts in position as against both of these adexact gravitational balance and precise symmetry of work holding'and grinding process is assured is carried out by means of opposed adjusting screws 180 in the ears 179 of the adjusting head 178 on the main supporting arm 45 (see Figs. .2 and 25). Lever screw 174 being temporarily released letting off on one. screw 180 and taking up correspondingly on the other a fraction of a turn, enables a very fine adjustment to be made, and a substantially perfect balance and distribution to The adjustments of the grinding mechanism G have already been described, except those adjustments which pertain to accessibility. The guide 63 is circular in crosssection and constitutes additionally a hinge pin 191 offthe frame 65. But one ear 190 may be removed to swing the grinding wheel downwardly from frame 65 through movement of the grinding wheel to an inordinate extreme position, as may be done either by disconnecting the connecting rod 80 (Fig. 12), or by swinging cover 36 outwardly, which of course disengages from worm gear 84. On its inner face, opposite the plane of the inner face of the frame 65, the bracket 62 carries the feltlined lubricating channel 192 which lubricates the faces of the two brackets as the reciprocate in sliding engagement.

Not only is my invent-ion adapted to grind straight toothed files of various shapes, but it is also adapted to grind curved toothed files of various shapes. A curved tooth file. is shown in semi-diagrammatic view in Fig. 11. Here, the ends 127 of the pawl 119, when at the upper end of its feed stroke, lie on the are 193 of a circle struck from the center 194 of the driving shaft 71 of the grinding mechanism. They lie, too, on the arc of the arc-shaped tooth root beneath which they engage, this are being struck. from the tooth center 195' located on the vertical gravitational axis 91 of the work (or some other line common to all the teeth). So, the file with curved teeth may be fed according to the method of my invention also in gravitational balance.

. In this grinding of curved teeth I use a.

I modified form of grinding mechanism G,

.inserting it's shaft 71 through the bracket 4.4

and replacing the gear 72. This mechanism consists of a bracket 195 fixed to the shaft 71 and carrying a fore extension 196 adjustably clamped to its under side and carrying the grinding tool 49 in a depending position by. means of a collar 60, and a bearing column 50 and a shaft 51 in all essential respects like the parts of similar numberin.

the othermechanism. By reason of the fixed connection of the supporting brackets 60' to the oscillatingshaft 71, when this shaft is oscillated, thegrinding tool 49 is oscillated, but instead of reciprocating on a straight line path, it oscillates on a curved path of'a radius of the distance of the plane of the grinding "tool 49 below the axis of the oscillating shaft 71.- This distance is adjusted by adjustment of the bearing column in the bracket 196-to make the radius of oscillation equal to the radius of the curved teeth of the file being ground. It -is the radius R in Figure 11. The grinding .wheel is shown in this figure in dotted lines in engagement with the tooth at the end of this radius. The angularity of the plane ofthe grinding tool with respect to the radius R i's'adjusted so that the same' conditions of location of the point of greatest depth 186 and-its path of travel with respect to the toothed edge, parallel to that edge and removed a distance back of it, and the same conditions of angularity of the plane of the grinding Wheel 'with respect to the edge of the tooth, and all the other outlined conditions, pertainhe're in'just the same manner in which they pertain in connection with the grinding of straight teeth. And .since the feeding pawl 119 needs engage below the tooth being ground by one or two teeth, the radius R, defining the are 193, is greater than the radius R, and the points 127 of the branches of the pawl lie at the point of intersection 0am 193 with the arc of the tooth engaged by the pawls. Thus with the substitution of the oscillatable grinding mechanism G for the reciprocable grinding mechanism G, and the adjustment'of the pawl 119, the

' method of my invention may be practiced as fully and completely upon files with curved teeth as upon files with straight teeth.-

.' Reverting to the gearing shown in Fig. 12 for the oscillating of the grinding wheel 49 and of the movement ofthe feeding pawl 119, it may be said that Fig. 22 shows in transverse section the cam 81, its mounting on the *2 cover plate 36, and its removable coupling in' gravitational balance may be substantially wholly by the vertica disposi-- with the worm gear 83. This removable coupling is by means of flat headed pin 196 screw threaded into the cam and securing the connecting rod thereon. The fiat head is entered into a slot 197 formed in the outer face of the worm gear 83. Thereby when the cover plate 36 is swung on its hinges, cam 81 is at once, uncoupled by the movement of the flat head 196' out of its slot 197. Thereupon the grinding mechanism may be freelyoscillated and adjusted, and the feeding.

mechanism may be operated, all by hand, to place everything in working order before turning on the power.

A stub shaft 82 is carried in the boss 198 ofthe hinged'side 36 of the casing 35 by means of a bearing sleeve 199 having a force fit therein. Stub shaft is retained in the sleeve by the knurled head 200 clamped on its outer end, and by means of which the grinding and feeding mechanisms may be manually operated- Lubrication is by means of 011 holes 201 normally closed by a spring ring 202.

Referring to Fig. 23, it will be seen that the micrometer shaft 176 is retained in place by a bearing of an inside collar 177 and a head 175, respectively, upon the opposite ends of a bearing sleeve 203. This sleeve is .of.slightly larger diameter than each the collar 177 and the head 175, and is held inplace within the bore 204 in the vertical branch of the stirrup 34 by means of the set screws 205. By simply removin the set screws this entire micrometer ad ustment may be removed in entirety, along with the shaft whenever desired.

Too, it should be noted that Figs. 6 and 8 pertain particularly to the holding clamp adapted to hold in place straight toothed files. These files usually have parallel side edges, and the right hand edge is held firmly up against the extended guide 105-'B connected with the right hand jaw 104by the .pressure of the steel. spring 105A.

With proper relation ofthe guide 105B and the pressure of spring -105-A, as adjusted by the movement of the jaws 104 toward each other,.the maintenance of the file reserved tion of the ide 105B against which its edge bears uring the entire feeding movement. In such case I have used, and in some cases prefer to use, a feeding pawl having but a single prong 125 instead of a double .just the feeding pawl by means of the adj ustment 124 provided as to locate the single feeding pawl on the gravitational axis llne 91 (see Fig. 11) and thereby'avoid dissymmetry of application of the feeding force which might tend todisturb in any way the continuing'gravitationai balance of the file against the straight edge 105-43.

Figs. 7 and 9 pertain particularly to the holding and feeding ot the curved tooth files shown in diagram in Figs. '11 and .18. In this case, owing to the fact that the teeth are curved, and the fact that a very precise lateral adjustment of the file would have to be carried out in each case in order to insure a grinding parallel at all times to the are shaped edges of the teeth, and owing to the furtherfact that even a slight variation in the width of the file, or any parallelism between its ofiset sides, would result in a variance from this essential parallelism of the arcs of grinding and arcs of the edges of the teeth, I prefer to employ the double pointed pawl 125 illustrated in Fig, 11, and to adhere to the location of this point at the point of intersection of the radius Rf;

and R of the engaged tooth edge, respectively., :I prefer, too, not to use a guide 105-B or even a 5 ring 105 -A, but, instead, to provide the aws 104 with the wearing workifaces 1 09, and to so: adjust them that there is a clearance on each side of the work, as indicated inFig. 11, whereby the work automatically adjusts itself about the points 127, the points 127 defining accurately the 'positiorr of the arc shaped edges of the teeth with respect to the path of rinding, and retaining this definition t roughout the feeding Toperation. The

. K slight play necessary to insure this automatic perfection of the adjustment is insuficient to an extent sufiicient to enable the grinding otherwise, the,

wheel 49 to engage the work freely in a path directly opposite the clamping jaw 111, and approximately centrally of the clamp itself whereby the ap lication of the friction clamping force and t e grinding are both carried eut symmetrically with respect to the central axis of the clamp; or, stated inding is carried out about thecentral axis before application of the clamping friction. The slot designated 206' is in the one case curved and in the other case straight, according to the shape of the path of" movement of the grinding wheel.

'Too, it? should be noted, in closing, that there is especial merit in that feature of my method according to which the file is operated on from a top end down, being engaged first at its top end and fed vertically upward.

Not: only is the gravitational balance the more quickly and eifectively established, and the grmding operation started off in perfect alignment and adjustment, but also any foreign matters between the teeth are promptly dropped since the teeth are pointing downwardly, all dust is prevented from lodgment in the teeth, the teeth more effectively engage the faces of the clamp and hold the work firmly sustained from its frictional engaging faces much more effectively than if the teeth were pointing up, and they might slip: freely past the engaging surfaces without biting into them, and, finally, the entire organization of the machine is rendered decidedly more practical since the main bodies of all of the mechanisms can be located nearer the base of the machine, giving a low center of gravity, and since, when the grindingoperation takes place at the top of the machine, the

operation and all of the immediately associated mechanisms is. the more open for ful inspection and adjustment.

There are, as usual, advantages of my in 'vention which I have not taken the opportun:

ity to mention'for the sake ofv brevity, and still others which are so obvious asfnot to need mention. The outstanding advantages are so great, however, as to ma e going into the auxiliary or lesser advantages of little moment in connection with the exposition of the method at large, and this preferred form of machine for carrying it out. The machine has proven so very useful and the work of such a high order and the saving of file renewals, through its use, so great that it; is probable an unusual number of ways and means may be 'devised to modify it to meet special conditions, or to meet competition, and for various other unusual ends. Without doubt the invention is susceptible of a large number of modifications with the same and perhaps with attendant advantages. All modifications not diverging from the generic: spirit of my invention I shall endeavor to cover in the annexed claims. Particularly do I wish it understood that while I hate described and claimed my invention with particular reference to file grinding,the applicability of the prior art as respects machines for grinding toothed work of other'description and of a great variety indicates it is probably applicable in some phases to the grinding of other varieties of toothed work. The claims should, therefore, not be limited by their circumstantial terminology to the application of .the invention to the grinding of files, except in so far as the prior art anticipates the generic spirit of the invention. I

I claim: L1. The method of grinding files having non-rectilinear edges which consists maintaining the filevertically in gravitational balance before the grinding tool throughout grinding member.

the grinding operation, and avoiding general lateral guiding.

2. The method of grindingfiles having a substantial axis of symmetry which consists in maintaining the article before the grinding tool gravitationally balanced vertically about said axis of symmetry, applying 'a feeding force substantially parallel to said axis and symmetrically distributed with respect thereto, and avoiding general lateral guiding.

3. A file grinding machine comprising a grinding tool, a friction clamp arranged to hold the'work before saidtool, a feeding member adapted to engage the teeth of the work and feed it forward through the holder which feeding member has a reciprocatory movement comprising forward and back strokes, positive means for carrying the feeding member through variable back strokes of alength unequal to the distance between teeth, and impositive means for carrying the feeding member through its forward strokes, together with means fixing in space the end of the forward stroke of said member, the grinding tool being arranged to operate upon a-file tooth directly engaged by the feeding means.

4. A file grinding machine comprising a grinding tool, a friction clamp work holder to hold the work before the tool, a reciprocable feeding member to carry the work forward tooth by tooth through said friction holder, a stop establishing a fixed point for the extreme forward movement of said feeding member, positive driving means for said feeding member on its back stroke and impositive' driving means therefor on its forward stroke, the grinding tool being arranged to operate upon a file tooth directly engagedby the feeding means.

'5. A machine for grinding files comprising a trav'ersable grinding member and a 'universally adjustably supported file-supporting member, means for traversing said grinding member, means for obtaining rough and fine adjustment of said supporting member in various directions, and power operated means adaptable to said adjustment forfeeding a file tooth by tooth through said supporting member at each traverse of said 6. A machine for grinding files comprising a" clamping member for frictionally holding a file and a grinding member traversable .yrelative thereto, means for causing traverse of said grinding member, means for feeding a file through said clamping member relatively to said grinding member, said means being operatively supported in a casing car- ..rying said grinding member, part of said means being carried on a hinged cover of said casing. Y

7. In a file grinding machine comprising a traversable rotaryfgrindin member and a clamping member for frictlonall-y retaining a file to .be ground, common means for traversing said grinding 'member and for feeding said file through said clamping member to present successive teeth to said-grinding member, said means being normally 'actuated by means which drive said rotary grinding member, but disconnectible theretoothat each traverse of said wheel thereover, both of said means and the wheel being actuated from a common source.

9. In a machine for grinding flat faced milled files, means to support a fiat face of a file to be ground in a determined plane, a grinding wheel oscillatable about an axis transverse to said plane with the periphery of-the grinding wheel tangent to said Plane, means to relatively feed the support and the wheel, and means to relatively adjust both tllle support and the axis parallel to said ane. p 10. In a machine for grinding flat faced milled files, a grinding wheel reciprocable parallel to a determinate plane which is tangent to the periphery of the grinding wheel,

and on a determinate path, means to support vthe flat face of a file to be ground in said and on a determinate path, means permanently secured to the machine to support a file with its face in said plane, means to relatively feed the support and the wheel, and means to relatively laterally adjust said support and path of movement with respect to each other parallel to said plane without disturbing the permanent securement of the support to the machine.

12. In a machine for grinding fiat faced milled files, a grinding wheel reciprocable parallel to a determinate plane which is tangent to the periphery of the grinding wheel and on a determinate path of tangency, means to support a file with its face in said plane, a feeding device for feeding the file, and means to relatively laterally ad-'