US2257501A - Grinding machine - Google Patents

Description

Sept. 30, 1941. F. J MERsQN 4 GRINDING MACHINE Filed Oct. 22-, 1958 5 Sheets-Sheet aw w g Q .1 6 w, fl 00 74. 4 aw I m 1w 1 oflam w u M o 88 9 0 oh w .31 .5 a 9 2 3 9 E w m4 2 4 w m 1 i 8 3 0 1 0 Wm m W. 9 50 Q aw 4 H T .H. m u/ 0 6 M INVENTOR Francbl efimafl ms ATTORNIEY Sept. 30, 1941. F. A. JIMERSON I GRINDING MACHINE Filed Oct. 22', 1938 5 Sheets-Sheet 2 Fran INVENTOR cg siejl'mersan BY F HIS ATTORNEY Spt. 30, 1941.] 5 "F. A. JIIMERSON GRINDING MACHINE Filed Oct. 22, 1 938 5 Sheets-Sheet 3 INVENTOR I ranawl Jzmerson HIS ATTORNEY Sept. 30, 1941. F. A. JIMERSON I GRINDING MACHEIINE Filed Oct. 22, 1938 5 Sheets-Sheet 4 INVENTOR ancisl ejmzem on HIS ATTORNEY Patented Sept. 30, 1941- GRINDING MACHINE Francis A. Jimerson. Athens, la., a'seignor to Ingersoll-Rand Company, Jersey City, N. corporation of New Jersey Application October 22, 1938, Serial No. 236,518

Claims.

This invention relates to grinding machines, and more particularly to a grinding machine for sharpening and gauging drill bits of the detachable type.

One object of the invention is to facilitate the operations of placing the drill bit von the grinding machine and removing it therefrom.

Another ,object is to enable the grinding machine to be readily adjusted to accommodate drill bits of different sizes.

Still another object is to effect the automatic removal of the drill bit from contact with the grinding wheel upon completion 'of the grinding operation.

Other objects will be ,in part obvious and in part pointed out hereinafter. I

In the drawings accompanying this specification and in which similar reference numerals refer to similar parts,

Figure 1 is a front elevation, partly broken away, of 'a grinding machine constructed in accordance with the practice of the invention,

Figure 2 is an end elevation, partly broken away, of the form grinding wheel and its work holder, I

Figure 3 is an elevation, partly broken away, showing a front view of the profile or form grinding wheel and its work holder,

ing machine comprises a frame 24 upon which is mounted, among other elements, a motor II that drives the grinding machine. On the top of the frame 24 is a tray 24 and a mounting 21 for. the grinding and feeding elements of the machine.

. The mounting 21 comprises a casing 28 having end walls 29 and it in which are apertures 3| and 32, respectively, to accommodate a shaft 33. The ends of the shaft extend exteriorly of the casing 28 and carry grinding wheels .44 and 35. On the portion of the'shaft 33 lying between the walls 29 and 30 is a sheave 38 which Figure 4 is a plan view of the gauge grinding end of the machine,

Figure 5 is an end elevation of the gauge grinding portion of the machine,

Figure 6 is an enlarged longitudinal view, in elevation and partly broken away, of the gauge grinding portion of the machine,

Figure 7 is a transverse view taken through the work gripping element on the line 1-1 in Figure 6, I

Figure 8 is .an elevation. partly inv section, taken through Figure 1 on the line 8-8 and showing a driving connection,

Figure 9 is a transverse view taken through Figure 8 on the line 9-9,

Figure 10 1s a transverse view taken through Figure-5 on the'line Iii-l0, and

Figure 11 is an elevation, partly in section, of a detail.

Referring more'particularly to the drawings, 2! denotes the grinding machine in its entirety and II the work piece shown as being in the form of a detachable drill bit of the cruciform type and ha ving the usual gauge surfaces 22 and cutting edges 23 on its wings which the grinding machine is intended to redress.

is aligned with a sheave 31, on the motor shaft II, and a pair of belts 39 are trained over the" sheaves 38 and 31 to transmit movement from the motor'to the shaft 33. Preferably the apertures II and 12 are of considerably larger diameter than the shaft to accommodate housings 4 0 and 4|, respectively, for bearings 42 of the anti-friction type which are held against-shoulders 43 on the shaft by nuts 44 threadedly engagingthe shaft 33. The hous ing's 4i! and 4! are connected to the casing 28 .by bolts 45.

One of the openings in the casing 28 through which the shaft extends, in this instance the opening 32, is of ample diameter so that whenever a belt requires attention it may be moved or inserted through the opening 32. v

In a more specific sense the grinding wheels l4 and 45 are, respectively, profiling or forming andgauge grinding wheels. The wheel 34 has a substantially V-shaped periphery that corresponds to the notches or spaces between the cutting wings of the drill bit. More specifically,

the periphery of the'wheel 34 hastwo inclined surfaces 46 that converge in the middle of the wheel and the inclination of these surfaces conform with that of the sides of the cutting wings. The degree of inclination of the surfaces 46 de- 7 pends, of course, upon the type of bit for which the wheel 34 is intended and may be variedby suitable dressing apparatus in a manner well understood. The grinding wheel 34 is secured to and held in concentric relaticnship'with the shaft 34' by the usual cheek plates 41, and a spacer 4| acting against the outermost cheek plate 41 serves as a seat for a nut 40 threaded on the end of the shaft 38 to clamp the wheel 34 securely between the cheek plates 41.

'me grinding wheel 44 is enclosed by a ll mountedon theouter side-ofthe wall II of In the form of the invention shown, the grind-, the casing 24 and having an aperture 5| through which the shaft 33 extends. In the opposite end of the guard 56 is an opening 52 to permit of access to the grinding wheel and said opening is normally closed by a cover plate 53. In the front or working side of the guard is an opening through which the work piece, such as the drill bit- 2 I may pass to contact with the grinding tached pivotally thereto by a bolt or rod 51 extending through one lug 56 andthe holder 55 and threaded or otherwise afllxed to the other lug 56. The bolt 51 is longer than the combined 'wldthof the elements through which it extends and on the projecting portion of the bolt is a coil spring 58 which tends to'balance the weight of the work holder 55 in order to prevent a too free pivotal movement of the work holder about the bolt 51.

One end of-the spring 58 is anchored to the work holder and the other end of the spring to a washer 58 that seats against the head 68 of the bolt 51 and held against rotary movement with respect to the bolt in any' well known manner. 4

The'portion of the work holder 55 engaging the bolt 51 constitutes a rocker 6| and has a pair of wings 62 which lie on opposite sides of a hearing block 63 carrying a handle 64 for rocking the work holder about the bolt 51. The block 63 desirable since it is inadvisable to permit of extended period of contact between the work and the wheel because of danger of burning-the work,

or glazing the grinding surfaces. The drill bit is, in consequence, thrust against the grinding wheel for only a brief period and then quickly withdrawn. As will be readily appreciated, this 7 requires a succession of oscillations of the work holder at close intervals and may be accomplished with less fatigue to the operator if both.

the hand and foot are used to actuate the work holder.

Inasmuch as the work holder is mounted upon the guard 58 it is essential that these elements be shiftable relatively to the grinding wheel 34 to make possible the correct position of the work' holder with respect to the grinding face, otherwise the angular relationship of the arbor 65 to the grinding surface of the wheel would change accordingly as the diameterv of the grinding wheel diminshes through wear "or with difl'erent lengths of work pieces. In further'ance of this end, means are provided to enable the guard to be moved laterally of the grinding wheel and comprise a slide 18, of dovetail shape, which may be an integral portion of the guard 58 or formed as a separate member and suitably attached to the guard. The slide 18 is arranged in a guideway I8 in the side of the casing 28 and the guideway thus forms the sole support for the guard. A screw 86 in threaded engagement with a lug-8| on the slide I8 serves to move the slide 18 longitudinally of the guideis bored to receive an arbor 65 of which an end 66 extends into the drill bit 2| to support it for grinding. The arbor 65 may be freely rotatable in the bearing block 63. Ithas a collar 61 that seats against one end. and a knurled knob 68' abuts the other end of the bearing block to prevent endwise movement of the arbor with respect to the bearing block. The knob 68, moreover,

' serves as a convenient grip member for rotating on for clamping the wings 62 securely to the sides of the bearing block. The foregoing arrangement makes possible a quick adjustment of the bearing block in instances where the profile of a working bit requires a-certain-angular position of the arbor 65 with respect to the working face of the grinding wheel 34 in order to avoid the formation of high or low centers on the drill bit. 3 Although the work holder 55 may be oscillated about the pivot bolt 51 by means of the handle 64 it has been found advantageous to provide means whereby the work may be performed in part by pressure of the operators foot. To this end the rocker 6| is provided with a lug. 13 having a depression I4 to receive theend of a rod 15 of which the opposite end rests upon a treadie 16 mounted upon a bar I? on the frame 24.

The handle 64 and the treadle l6 afford a choice of means for applying -force to the work holder to move it, toward the grinding wheel or, as has been found to be a preferred mode of operation, the treadle may serve to move the drill bit toward the grinding wheel and the handle 64 to retract the drill bit. This division of labor is way 18.

The screw 88 is provided with a handle 82 located conveniently near the operator's position for rotating the screw, and a pair of collars 83 attached to the rearmost end of the screw 88 and lying on opposite sides of a rib 84 on the adjacent portion of the casing 28 serve to hold the screw 86 against endwise movement.

Sufllcient clearance exists between the collars 83 and the rib 84 to enable the screw 86 to be rotated freely. Thus, whenever it becomes necessary to move the guard and the work holder 55 to a new position, as for a redressing of the grinding wheel 34 or the replacement of the grinding wheel with one of larger diameter, the

screw is rotated in the required direction to move the guard toward or away from the grinding wheel. a

The wheel 35 differs from the wheel 34 principally in that it has a substantially true cylindrical grinding surface. It is supported and held in concentric relationship with the shaft 33 by 45 securing the bearing housing 4| in position, and in the opposite end of the guard 88 is an opening 88 that is normally closed by a' cover plate 80.

The guard 88 also preferably serves as a I mounting for the devices which support the drill bit during the grinding thereof and effect feeding movement of the drill bit with respect to the grinding wheel. The guard 88 accordingly v has an integral, sleeve 9| which extends longitudinally of the machine, at a lower elevation than the shaft 33, and in the sleeve 8| are a pair of bushings 82 which serve as renewable bearing surfaces for a reciprocatory rod 93.

aes'asoi The rod may be freely rotatable in the bushings 92 and supports a work holder denoted in its entirety by 93. The work holder is mounted on a bracket 93- attached to the rod 93 and comprises, as casing parts, a head 93 and a cap 91 seated on the end of the head 93. On the opposite end of the head 93 is a reduced extension 93 ofwhich the periphery serves as a bearing surface for a collar 99 forming an'integral portion of a bracket I positioned in front of the grinding wheel 33 and above the sleeve 9|. The collar 99 is split and is clamped fixedly to the extension 93 by a pinch bolt IOI.

In its assembled position the bracket I00 lies directly beneath the drill. bit 2I so that when the drill bit is released from the work holder it may drop upon the bracket I00 and thence roll over the upper surface I02 of the bracket which is inclined toward the tray 23.

- confronting the drill bit 2I is a bearing I03 of the anti-friction type in which is inserted a cup I05 having a flange I06 seating against the inner surand has arranged thereon a pair of anti-friction bearings I3I that are held on the stem I by a washer I32 held in position 'by a screw I 33 threaded-into the end of the stem I30.

The outer races of the bearings "I are slidably in the open end of a cup I33, slidable in the cap 91, and containing a spring I 33 that seats against the outer race of the innermost bearing I3I and acts, in the relaxed position of the grip ping elements, to maintain the outer-race of the outermost bearing I3I in abutment with a spring ring I33 arranged in the mouth of the cup I33 to retain the bearings III in the cup.

The spring I33, in effect, is a resilient transmission member and serves the function of transmitting force to the expander for driving the keys II9 against the drill bit and such force is applied to the spring I33 and the train of elements leading to the keys II9 by a toggle I31 attached to the cup I33. V

In order to control the tension of the spring I 33 the cup I33 is adjustable relatively to-the ace of the arm to exclude abrasive matter from the bearing I03. A packing-member I01 between the flange I03 and the bearing I03 serves as further protection for the bearing I03.

In the periphery of the cup, near its innermost end, is a spring ring I03 which seats against the inner race of the bearing I03 to lock the bearing to the cup and thereby make it possible to remove both from the arm as a unit.

The inner race of the bearing I03 may, moreinterior I09 'of the cup-serves as a receptacle for thestem IIO of a center I II having grooves II 2 in its end surface to accommodate the cutting edges 23 of the drill bit. A spring ring I I3 engaging the stem H0 and the wall of the bore I09 holds the center I II against 'endwise movement with respect to the cup I03.

. The center III is freely rotatable with the drill bit 2| which is supported in grinding-position over, be fitted snugly on the cup I03 and the by a chuck I I3 threaded into the end of a hollow spindle II3 extending longitudinally of 'the head the chuck 3 comprises, for example, a stem 93 and into the cap 91. The gripping element of H3 which extends into the socket II1 of the drill bit 2| and hasa series ofnradial slots H3 to accommodate keys "-9 which arecollectively encircled by a garter spring I20 tending to move the keys I I9 toward the axis of the *chuck. The

' inner-surfaces I2I of the keys II9 seat upon the a head I23, at its innermost end, slidable in an enlarged portion I 23 of the bore I23 in the spindle II3. A spring I23 encircling the expander acts against the head I23 with one end and with its other end against the chuck II3 to move the expander for releasing the keys I I9. I

. The remaining portion of the bore I 23 is of reduced diameter and contains a rod I21 slidable therein to actuate the expander I22. On the end of therod I21 adjacent the head I23 is a collar I20 which is slidable in the enlarged portion I23 and is held on the rod by a screw I29,

. the head of which may abut the expander to transmit motion thereto. The opposite end of the toggle. I

'gauge surfaces 22. i the outer race of an anti-friction bearing I31 seated in a lower wall I33 of the head 00 and toggle. A preferred mode of accomplishing this is to thread the cup upon a bolt I30 the head of which ispivotally connected to a pin I 39 seated in'a pair of wings I30 on the toggle I31; A nut m 'on thebolt m seats against the end of the cup I 33 and locks the bolt to the cup.

The-ptlrtions of the wings I30 through which the pin I39 extends constitute one end of the toggle I31. On the other end of the toggle and lying in parallelism with the pin I39 are trunnions I32 that extend pivotally through ends of straps I33 arranged above and below the $088 and having their other ends pivotally connected to pins I33 in the upper and lower surfaces of the cap '91. The straps I33 may be held on the trunnions I32 and the pins I33 in any suitablemanner, as by cotter pins I33 placed in-the ends of the trunnions and the pins. IA grip member I33 on the toggle I31 provides a convenient lever for rocking the toggle about the trunnions I32.

The straps I33 are of suitable length to avoid sharp side thrust of the cup I33 against the wall of the cap 91 and, therefore, excessive'wear upon the cooperative surfaces of these elements as a result of the repeated movement of the cup in the cap 91 incident to the operation of The work holder 93 is pivotally mounted upon the bracket 93 so that it may be angularly adjusted with respect to the-grinding surface of the wheel 33 in accordance with the angle of the In the arrangement shown extending part way into a bore I33 in the bracket f 93 serves to centralize the head 90 with the bracket; On the portion of the head 00 adjacent the bracket 93:are flanges I30 which seat upon flanges .I3I on the bracket 93 and have arcuate slots I52 to receive clamp bolts I33 threaded into the flanges I3I. The slots I32 are of ample tated by different angles of gauge surfaces 22.

The operation of the work holder 1 to the correct angular position with respect to the grinding surface of the wheel 33 may be quickly (accomplished by partly unthrea'dingethe screws I33 and rotating the work holder about its axis until the gauge surface of the drill bit lies flush against the grinding surface of the wheel 33; After the work holder has been thus positioned the flanges I30 and III are again clamped together for holding the work holder immovable with respect to the bracket 95.

The bearing I41 serves its usual function as a I51 to prevent relative rotary movement between.

the two, and the sleeve I51 is supported b'y anti- Y of transmitting the power required for reciprofriction bearings I90 and lil .in the cap91 and a the head 99, respectively. I

Suitable packing members I82 and I93 are placed in the extension 99 to encircle the spindle H5 and the sleeve I51, respectively, for preventing the passage of abrasive matter into the head 99 The lower end of the shaft I54 extends into .a bore I94 in the rod 93 and has a reduced extension I95 carrying; a pinion I99 which abuts an anti-friction bearing I51 in the adjacent portion ofthe bracket 95. A spacer I 99 encircling the shaft I54 abuts the bearings I91 and I41 to prevent endwise movement thereof with respect to the shaft I54.

The shaft I54 and associated gearing constitute parts of a train of driving elements for effecting constant rotary movement of the chuck 'I I4 during the grinding of a drill bit. The power employed for this purpose is also provided by the motor 25 and is transmitted from the shaft 33 by a belt I99 and sheaves I10 and HI secured,"

respectively, to the shaft 93 and a counter-shaft I12 arranged in a gear casing I13 mounted on the frame 24. The shaft I12 is supported by anti friction bearings I14 and I15 in the gear casing I13 and carries a clutch disc I19. mentary disc I11 faced with friction material I19 is mounted upon a longitudinally shiftable shaft I19 disposed slidably in a'sleeve I99 supported by a bearing I9I on the frame 24.

-- supplies cooling liquid to the grinding wheels 34 and 95. The driving connections to=both are located in the gear casing I13and that acting to drive the rod 93 comprises a worm I99, on the shaft I12, meshing with a worm gear 200 attached tov a shaft 29I. 'I'he'shaft 20I is supported by anti-friction bearings 202 in the gear casing I13 and projects exteriorly of the gear easing into a crank 203 to which it is locked by a set screw 204.

In the outer surface of the crank 203 and extending longitudinally thereof is a 'T-slot 205 for the accommodation of a T-bolt 206 serving the function of a crank pin. The bolt 205 is readily adjustable'in the slot 205 and is clamped fixedly to the crank 203 by a nut 201 threaded on the bolt. K The bolt 209 is provided with a bushing 299 lying in the end of a connecting rod 209 of which the opposite end is connected to'a rocker arm 2I0 extending upwardly through the frame 24 and terminating in the longitudinal plane of the rod 93. A pivot 2 supported by the frame 24 extends through an intermediate portion of the rocker arm, and in the upper end of the rocker arm is a pivot 2I2 to which is connected an end of a link 2I3 having its other end connected to th rod 93. V

The link 2I3 is adjustable and comprises a yoke 2| 4 which is attached to the pivot 2| 2 and threadedly connected to a screw 2I5 having a ball head 2I9 which lies in a partly cylindrical socket 2" in the rod- 93 and is held in the socket by a bushing 2I9 threaded into the rod. Thescrew 2I5 carries a knurled flange 2I 9 to enable the screw to be conveniently rotated with respect to the yoke 2, and a. lock nut 220 on the screw and seating against the end of th yoke A comple- The shaft I19-is moved, for separating the clutch discs,'by force applied to'a treadle I92 mounted upon the lower portion of the frame 24. I

.A link- I83 connects the treadle to an arm I 94 of a bell crank I95, and the bell crank rocks upon a pivot I99 on the frame 24 and has an arm I91 to engage a collar I99 on the shaft I19 for moving the clutch disc I11 out of contact with the clutch .disc I19. A spring I99 interposed between the collar I89 and the end of the sleeve I90 acts to move the shaft I19 towardthe shaft I12, and a spring,l90 secured to the frame 24 and to the treadle I92 normally maintains the treadle in- .ment the sheave may at all times remain in alignment with a sheave I92 on a shaft I99 extending longitudinally ofthe bore I94 in the rod 99. A belt I94 trained over thesheaves Ill and I92 transmits motion from the shaft I19 to the shaft I99, and a pinion I95 on the innermost end of theshaft I93 meshes with the pinion I99 for delivering power to the shaft I94 and thus to' the work seated in 'a' sleeve I91 threaded into the end of the rod .3. l An additional service of the shaft I12 is that iiolder. Preferably, the shaft I99 is provided .with anti-friction bearings I99 which are 2 locks 'the screw 2I5 against unauthorized rotation with respect to the yoke 2 I4. 'The link 2I 3 provides a convenient means for adjusting the range of movement of the drill bit with respect. to the grinding surface of the wheel 35. As will be appreciated, it would be undesirable to reciprocate the gauge surfaces of the drill bit to move into and out of the plane of the grinding surface of the wheel. In practice, therefore, the link 2I3'is so adjusted that the gauge surfaces never move entirely out of the plane of the grinding surfac and this may be conveniently accomplished by shortening or lengthening the The pump I99 which, as previously stated is. also driven from the shaft I12, is of the submergible type. It extends into a tank 22I form- 'ing a reservoir for cooling liquid and has a discharge pipe 222 which may lead to the grinding wheels 34 and 35 to' deliver liquid to the grinding surfaces. In the arrangement shown the. pump is supported by the gear casing I13 and connected thereto by a distance piece 223 which houses a pump shaft 224 carrying a pinion 225 that meshes with ,a pinion 229 on the shaft I12. Unlik the work holder 55, which is actuated by manualpressure, the work holder 94 is actuated mechanically for feeding me work toward the wheel 35.. Such movement is heated in stepby-step 1 fashion by means including a ratchet wheel 221 integral with or suitably attached to a cm 229. The ratchet wheel and the cam are mounted-rotatively on a shaft 229 and the ratchet wheel carries a hand-wheel 290 for rotating the ratchet wheel and the cam. 229 manually on the shaft 229. The shaft '229 extendsinto and is amxed, as by means of a set screw 23l, to an arm I grinding surface of the wheel 34.

232 having a bearing portion 233 which encircles the free end of the rod 93 and is held thereon by a'shoulder 234 on the sleeve I91.

The am 232 extends along the side of the grinding m'achine'and carries, at its rearmost end, a pair of rollers 235 which embrace a rod 236 supported by the mounting for holding the arm 232 against rotative movement with respect to the rod 93. The arrangement is such that during the reciprocatory movement of the rod 93 the rollers 235 will roll along the rod 236.

The cam surface 231 of the cam is in the form of an involute and moves or rotates under a camfollower 238 carried by a bell crank 239 attached to the arm 232 by a pivot 249 extending through the angle of the bell crank 239. The high and low points of the cam surface 231 lie directly on opposite sides of a notch I which accommoe dates the cam follower 238 in the non-feeding position of the work holder, and in the periphery of the ratchet wheel 221 and in the same radial plane as the notch 24I is a blank surface 242 which forms'a rest for a pawl 243 adapted to engage the teeth 244 of the ratchet wheel.

The pawl 243 lies in a substantially horizontal plane abovethe ratchet wheel 221 so that it may drop into ngagement with the teeth 244 by. gravity and is pivotally connected to an end of a rocker arm 245. The rocker arm is of V-shape and is secured pivotally to the bearingportion of the bracket 95 by a pin 246. On the intermediate portion of the arm 245 is a button 241 engaging the end of a spring 248 of which the other nd is connected, in the present instance, to a pin 249 on the tray 26. Thus, as the rod 93 moves to and fro the rocker arm 245 will be caused to tilt and in that way shift the pawl 243 to new positions on the ratchet wheel.

The arm 245 is rocked about the pivot 245 by a buffer. 259 lying in the path of the elbow 25I of the rocker arm. The buffer is slidably adjustable in a bore 252 in a casing part of a machine, as for example the sleeve 9 I,- and is locked in the different positions to which itmay be adjusted by a set-screw 255 threaded into the sleeve 9I.

The cam follower 238 is held, with a required degree of firmness, against the cam 228 by a spring 251 attachedto a lug 258 on the bearing portion of the arm 232, said lug being one of a pair that serve as guides for the end of the bell crank 239 carryingthe cam follower 238. The other end of the spring 251 is connected to a clip 259 secured to the free end of the other arm 269 of the bell crank.

To the end that the work holder may be readily adjusted with respect to the grinding wheel 35 for placing it in approximately the correct grinding position for a drill bit of a given diameter the bracket 95 is connected to the arm 259 of the bell crank 239 by an adjusting screw 26L The screw 26I carries a hand-wheel 262 for rotating .it

and is journaled in a bearing 253 having a trunmom 264 rotatable .m the bracket 95. The threaded portion of the screw engages a nut 255 arranged in" a slot 266 in the bell crank and having trunnions 261 extending rotatably into the arm 269. v

In the operation of the device, a drill bit 2i is v placed 'on the arbor 66 and the work holder 55 is 70 then oscillated about the pivot" '51 to place the ,cutting teeth of the bit into contact with the After the contiguous sides of a pair of cuttingwings have been ground the arbor 66 is rotated to a new position to bring other surfaces of the cutting teeth into position for grinding.

This operation may be repeated until all th sides of the cutting wings have been ground. The

5 drill bit 2| is next placed on the chuck H4 and the toggle I31 is then rocked about the trunnions I42 to move the chuck II4 toward the center III.

This movement of the toggle imparts pressure.

through the spring I35 to the rod I21 which will 19 act against the expander I22 and cause the keys I I9 to be pressed outwardly against the skirt of the drill bit for securing the bit to the chuck I I4. The force imparted bythe toggle for actuating the chuck mechanism will also causethel5 wings of the drill bit to, be pressed firmly into the grooves II2 of the center III.

During the placing of the drill bit on the chuck I I4 the treadle I82 is depressed 'to break contact between the clutch discs I and I11 so that the ,2 chuck II4 will remain stationary. After the drill .bit has been securednto' the chuck the treadle I82 is released and the spring I89 will then shift the shaft I19 to reestablish frictional contact benecting train of elements, to the chuck II4 for rotating it. I v a In the event that the spacing of .the work holder 94 with respect to the grinding surface of the wheel is unsuited for a drill bit of a given diameter the screw 28I may be-rotated to tilt the work holder the distance required to bring the gauge surfaces 22 of the drill bit into contact with the wheel. The ratchetwheel 221 35 may then be given a partial turn to move the 'blank surface 242 from beneath the pawl 243 and to -bring a ratchet tooth into position for engagement with the pawl. This movement of the ratchet wheel will also move the low point of the 40 cam surface 231 beneath the follower 238. I

During the ensuing operation of the machine the chuck will be constantly rotated and will reciprocate relatively to the grinding wheel to distribute wear over the entire grinding surface of the wheel. On each inward stroke of the rod 93 the rocker am 245 abutsthe buffer 259 and will be rocked about the pivot 246 and cause the pawl 243 to rotate the ratchet wheel and the cam. Upon each thrustof the pawl 243 the follower 238 is raised slightly by the cam and the work holder is thereby moved toward'the grinding wheel 35 in step-by-step fashion. a

This operation will continue until the ratchet wheel has been rotated to a position in which the blank surface-242 again lies beneath the pawl. The notch 2 will then also reach a position beneath thecam follower 238 which will drop into the notch 24I thus permitting the spring 251, by ,its force exerted on the bell crank 239, to tilt the work holder away from the grinding wheel.

The devices effecting the different movements described herein operate in such manner that the gauge surfaces 22 will be nicely reconditioned during the time required by the ratchet wheel to make a complete revolution, and when the drill bit is completely ground pressure is again applied .to the treadle I82 to disconnect the shaft I19 from the shaft I12. The drill bit may then be removed and another placed on the chuck II4 preparatory to a new grinding operation.

In the event that the grinding wheel 35 be replaced with one of greater or less width the stroke of the rod 93 may be changed by moving the crank pin 296 to adiflerentposition in the e slot Ill. 'This may be quickly and conveniently done by unthreading the nut Ill 'and moving the crank pin toward or away from the shaft Ill and again clamping the crank pin to the crank 203 by means of the nut III. In this way i the stroke of the work may be nicely adjusted to assure utilization of the entire-grinding surface of the wheel and to preventuneven wearing the work holder, a feeding'device for effecting feeding movement of the work holder, means for moving the work holder with respect to the grinding wheel. means for actuating the feeding device in response tomovement of the first said means, and means controlled by'the feeding device fortilting the work holder from the grinding wheel upon completion of a grinding operation. a

2. In a grinding machine, a mounting, a grinding wheel supported by themounting, a work holder adjustable angularly with respect to the grinding wheel to change the axis of the work holder to an inclined position with respect to the axis of the grinding wheel, a reciprocatory member serving both as a support and a pivot for the work holder, a feeding device to rotate the reciprocatory member during alternate strokes of the reciprocatory member for effecting a stepby-step feeding movement of the work holder, and means for automatically'causing actuation of the feeding device during a stroke of the reciprocatory member.

3. In a grinding machine, a mounting, a grind ing wheel supported by the mounting, a work holder, a reciprocatory support for the work holder, a rotary cam for tilting the work holder toward the grinding wheel, a ratchet wheel for the cam, a pawl on the reciprocatory support to engage the teeth of the ratchet wheel.*and an abutment on the mounting to engage the pawl during a stroke of the reciprocatory support and thereby cause the pawl to rotate the ratchet wheel and the cam in step-by-step fashion.

4. In a grinding machine, a mounting, a grinding wheel supported by the mounting, a casing,

a support for the casing, means for effecting reciprocatory movement of the support during the grinding of a work piece, means for rotating the support about its axis to actuate the work holder toward the grinding wheel, a work holder in the casing, a work-centering member in axial alignment with the work holder, a.bracket'affixed to the casing to support the work-centering member, a toggle 'to force the work holder into engagement with a work piece and to press such work piece against the work-centering member, a spring for transmitting force from the toggle to the work holder, and an adjusting dement, a bracket on the casing, a center in the bracket in axial alignment with the work-gripping element, a toggle for forcing the work-gripping element into engagement with a work piece and to force such work piece into engagement;v

with the center, cushioning means for transmitting force from the toggle to the work-gripping element, an adjusting device for the cushioning means to vary. the distance between the work holder-and the center, a feeding device for effecting feeding movement of the work holder,

and a driving connection in the reciprocatory support and the casing for rotating the work holder.

FRANCIS A. JIMERSON.

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