US2820331A

US2820331A - Grinding device

Info

Publication number: US2820331A
Application number: US565141A
Authority: US
Inventors: Billeter Henry Robert
Original assignee: Ammco Tools Inc
Current assignee: Ammco Tools Inc
Priority date: 1956-02-13
Filing date: 1956-02-13
Publication date: 1958-01-21
Anticipated expiration: 1975-01-21

Description

Jan. 21, 1958 H. R. BILLETER GRINDING DEVICE 4 Sheets-Sheet 1 Filed Feb. 15, 1956 @mW I WAN RAN IN VEN TOR.

ffsggg Ea Jan; 21, 1958 H. R. BILLETER 2,820,331

v V GRINDING DEVICE Filed Feb. 13, 1956 4 Sheets-Sheet 2 IN VEN TOR.

Jan. 21, 1958 R. BILLETER/ 2,820,331

GRINDING DEvIc I Filed Feb. 13. 1956 4 Sheets-Sheet 4 United States Patent 2,820,331 GRINDING DEVICE Henry Robert Billeter, Deerfield, Ill., assignor to Ammcp Tools, Inc., North Chicago, 111., a corporation of Illinois Application February 13, 1956, Serial No. 565,141

21 Claims. (Cl. 51-96) This invention relates to a grinding device and has to do more particularly with a machine for grinding arcuate contours, such as a grinder employed in dressingdown lined automotive brake shoes, and a new and improved workpiece holder therefor. J

Grinding devices for forming arcuate contours, such as automotive brake shoe grinders, commonly include a rotatable grinding element and a workpiece holder mounted for pivotal movement of the workpiece relative to the grinding element and in contact therewith whereby the grinding element forms an arcuate surface on the workpiece or dresses down an already arcuate surface.

The pivot is adjustable toward and away from the grinding element to determine the radius of the arcuate surface to be formed, but is adapted to be fixed or held in one position of adjustment relative to the grinding element during the grinding operation. In order to permit control over the amount of materialremoved by the grinding operation, the workpiece holder is so constructed as to permit the workpiece to be advanced or fed? toward the grinding element without disturbing the location of the pivot, and therefore without disturbing the pre-set radius of the arcuate surface.

In prior grinders and especially those employed in grinding automotive brake shoes, the workpiece holder has been adapted to hold the workpiece symmetrically and to feed the workpiece into a wheel-type grinding element in such a manner that the surface to be ground is advanced toward the grinding element in a direction perpendicular to the pivot axis and along a line joining that pivot axis and the closest point thereto on the grinding element. As the workpiece, for example, a brake shoe, is fed into the grinding wheel and pivoted while in contact there with so that material is removed from the shoe lining, the lining surface is ground as to be uniformly arcuate about the center of curvature for the brake shoe, this center point coinciding with the pro-set pivot for the workpiece holder when the shoe is symmetrically positioned in that holder. This operation is suitable and effective when dressing down or grinding the lining on a brake shoe adapted to be moved toward and away from a brake drum along a radius bisecting the arc of the lining, and when a lined brake shoe of that type is ground as described, it will properly engage the brake drum simultaneously along all portions of the length of the lining. However, many present brake shoes swing from one end about an anchor fixed within a brake drum, and pivot...

into engagement withthe'drum. For this type of shoe, merely grinding the lining to an arcuate contour does not necessarily insure the simultaneous contact of all portions of the length of the lining with the brake drum, since the brake shoe center of curvature will not always coincide with the brake drum center of curvature at the instant of contact of the brake shoe lining with the brake drum. For this type of brake shoe, the important reference point for the arcuate surface relative t'o'the shoe is not the brake shoe centerof curvature, but rather the fixedanchor or pivot for the shoe, a point which has a fixed position relative to the brake drum center of curvature.

The need for a fixed reference point for the brake shoe relative to the brake drum axis is even more critical when grinding brake shoe linings for used fixed anchor brakes wherein the drums have been machined to remove scorings or to restore true cylindrical contours to the drums. These drums have larger internal diameters than originally, and their brake shoes no longer match those brake drum diameters as well as theydid prior to themachining. Any differential in arcuate contour between the two must be absorbed by the lining, the surface of which must be brought to the arcuate contour of the drum, not the shoe. I Y 1 Since optimum braking efliciency can only be achieved by providing a maximum area of simultaneouscontact between lining and brake drum, a proper arcuate contour must be imparted to the lining in a manner suchthat the contoured surface is properly positioned relative to the brake drum and therefore to the fixed pivot or anchor of the shoe, rather than to the center of curvature of the brake shoe. This proper dressing down of the lining of a fixed anchor brake shoe is best accomplished byadvancing that lined shoe into engagement with a grinding element in a manner which simulates the movement of the brake shoe in a brake assembly.

An object of this invention is to provide a grinding device having a novel holder for pivotally advancing a workpiece into a grinding element, which holder itself is pivotally supported on a carriage having sliding rectilinear adjustment on a base toward and away from the grinding element for exact adjustment of the position of the holder pivot axis relatively to the grinding element.

Another object is to provide a grinding device having a novel mechanism for advancing a workpiece into a grinding element pivotally about an axis which can be positioned to accommodate a standard range of workpiece sizes and configurations.

A further object is to provide an-automotive brake shoe grinder of the turntable type having-a novel work holder for advancing a fixed anchor brake shoe .into a grinding element pivotally about the anchor recess of the; shoe itself, thus assuring a correct positioning of a predetermined a-rcuate contour on the lining of the shoe.

Another object is to provide an automotive brake'shoe grinder having a holder 'for pivotally advancing a brake shoe to be ground into a grinding element, which holder, is so designed and constructed as to easily and accurately accommodate and hold any standard size and 'configuration of brake shoe, and to correctly align the surface ofthe brake shoe lining with the grinding element for .proper dressing down of that surface.

A further object is to provide in a grinding device of the type having a workpiece holder mounted on a turntable for oscillatory movement about a turntable axis adjustably fixed relatively to a grinding element, of a pivotal advance mechanism by which the workpiece may be rapidly advanced to bring the workpiece into grinding relation with the grinding element, and by a simple manipulation secured in that advanced position and advanced In finely-controlled manner therefrom, which holder by another simple manipulation may be rapidly retracted from any position to which it has been advanced.

Yet a further object is to provide an automotive brake shoe grinder having a mechanism for pivotally advancing a fixed anchor brake shoe into engagement witha grinding element in a manner similar to that in which the subject shoe pivots within its brake drum.

.A still further object is to provide a device for grind- Ing arcuate contours, which device has a novel three-way means for associating a workpiece with a grinding element so. that a radius of curvature for the arcuate con- 3 tour can be accurately and positively 'set,'the workpiece pivotally advanced into the grinding element without disturbing the radius of curvature set, and the workpiece swung through an arc of engagement with the grinding element.

Another object is to provide a mechanism for pivotally advancing a workpiece into engagement with a grinding element, which mechanism is simple and sturdy, free from any requirement of delicate adjustment, and which can be easily mounted on a standard grinding device of the sliding carriage and turntable type.

Other objects and advantages of this invention will appear from a detailed description thereof taken in connection with the appended drawings, in which:

Figure 1 is a side elevational view of a brake shoe grinding device constructed in accordancewith the principles of the present invention, certain of the parts being shown as broken away and others sectioned to more clearly reveal the nature of the invention;

Fig. '2 is a perspective view of the brake shoe holder of the present invention mounted-on a turntable;

Fig. 3 is a fragmentary sectional view taken substantially on line 3-3 of Fig. 1;

Fig. 4 is a fragmentary sectional view taken substantially on line 4-4 of Fig. 2;

Fig. 5 is a rear elevational view of the brake shoe holder of Fig. 3, with a fragmentary diagrammatic illustration of the flange of a brake shoe engaged by the chuck;

Fig. 6 is an enlarged fragmentary sectional view taken substantially on line 6-6 of Fig. 3, with broken lines showing somewhat diagrammatically, and in exaggerated position for purposes of illustration, the relative position taken by the brake shoe when pivotally advanced about the anchor pin;

Fig. 7 is a sectional view taken on line 77 of Fig. 6;

Fig. 8 is a top plan view of the gauge of Fig. 6; and

Fig. 9 is a fragmentary top plan View showing the use of a modified form of anchor pin.

The grinding device of the present invention is especially well adapted for grinding to true arcuate contour the surfaces of linings attached to automotive brake shoes of the fixed anchor type, and the device is described here in in connection with such use for the purpose of illustration. It is to be understood that the invention is not limited to such an adaptation or use, and that the principles of this invention may be applied to other uses where generally similar results are desired. 7

It will be understood that the workpiece holder of the present invention is especially well adapted for use in a grinding device embodying a base, adjustable carriage and abrasive or grinding means similar to those disclosed and claimed in my copending application Serial No. 332,310, filed January 21, 1953, now Patent No. 2,734,319, granted February 14, 1956, to which reference may be had for a detailed disclosure of the construction and operation of such elements.

Referring now particularly to Fig. 1 of the drawings, the grinding device includes a base 10 in the form of an elongate, rectilinear casing-like member having a base flange 12 extending therearound from which there extend upwardly and inwardly, preferably at a slight taper, a pair of side walls 14, a front wall 18 and a curved rear wall 20. The top wall of the base constitutes a bed plate 22 upon which are mounted the principal operating elements of the device.

Supported within an opening formed in the top wall of the base 10 is an electric motor 16 which is suitably secured to the base as by means of a mounting bracket 27. and bolts 26. Current is supplied to the motor, as by means of a cable 28, and a conventional switch assembly is provided to control the motor circuit. The motor 16 serves to drive a grinding element 46, preferably in the form of. a cylindrical grinding wheel adapted to' dres's' down the surface of a brake shoe lining.

. A hood having an open front 52 is removably "se cured to the base 10 as by means of wing fastening studs 53, and substantially encloses the grinding element 45. The interior of the hood communicates through a series of passages (not shown) with a suction chamber and a dust collection chamber (not shown) into which air and comminuted products of abrasion are drawn.

A carriage 70 is slidably disposed on the upper surface of the bed plate 22 for adjustable movement toward and away from the grinding element 46. The carriage is substantially fiat in shape, and is formed with a flat circular turntable bed (Figs. -1 and 4) on which there is rotatably disposed a turntable 76 adapted to support a workpiece holder 80. The turntable 76 pivots about a turntable pivot axis established by a pivot pin 78 as explained more in detail hereinafter.

Means for accurately positioning the carriage 70 on the base 10 are provided in the form of indexing and adjusting means, as, for example, the means disclosed and claimed in my heretofore mentioned copending application. The external controls for these means comprise a knob projecting from one side wall 14 of the base and constituting a part of the mechanism by which the car riage is adjustably positionable in predetermined spacedapart index locations on the base, and an adjusting screw 62 fixed to the forward end of the carriage 70 and constituting a part of the mechanism by which the carriage is accurately adjustable onthe base intermediate of the respective index locations.

A reference mark 66 provided on the carriage cooperates with an index scale68 provided, for convenience. on a plate 69 attached to the side wall 14 of the base 10 to indicate to the operator the indexed location of the carriageonthe base, while a series of indicia provide a scale on the circular'periphery of the adjusting screw 62 to cooperatewith reference marks on stationary portions of the carriage, and indicate the distance the carriage has moved along the base from the indexing location in which the carriage'ispositio'ned.

The indexing 'locationsare so arranged as to establish spaced predetermined positions of the carriage on the base, and, accordingly, to establish corresponding predetermined positions of the turntable pivot axis relative to the surface of the grinding element. In the present illustrated embodiment, the indexing locations are spaced one-half inch apart, and are so located as to determine positions ofthe turntable pivot axis spaced progressively from the grinding element, ranging from 4 /2 to 8 inches therefrom. The index scale 68 is arranged and marked as to indicate diameters corresponding to the respective radii which the indexing holes establish between the turntable pivot axis and the grinding element. For example, when the reference mark 66 registers with the indicium 11 (Fig. l) on the index scale 68, and the adjusting screw is at its ier'o point, the pivot axis of the turntable is exactly 5 /2 inches from the surface of the grinding element. Radius-indexing increments one-half inch in length have proved to be satisfactory for the present embodiment, inasmuch as new automotive brake drums are commonly manufactured with diameters in one-inch multiples. In processing a lining on a brake shoe for a drum manufactured with a diameter not a multiple of whole inches, or for a drum which has been machined off a whole-inches diameter, the adjusting means must be used to complement the indexing means for establishing the correct grinding radius. Accordingly, should a brake drum of 'a manufactured diameter of 11" have been machined to remove material .060 inch in depth, the adjusting sc'rew must be manipulated so that the index and adjusting scales together indicate a brake drum diameter of 11.120 inches, or a distance of 5.060 inches between the turntable pivot axis and the surface of the grinding element.

Means are provided for securely locking the carriage to the bed plate 22 in any one of its adjusted positions, and for protecting the indexing and adjusting means from receiving any of the forces developed during a 3 grinding operation. These means may take the form disclosed in my above-mentionladen-pending, application, inwhich a rotatable thrust pin 82 (Fig. '1) constitutes a part of'clamp.v means releasably biasing the carriageand the base together.

Referring now to Fig. 4, theturntable. bed of the carriage 70 is provided with a circular track or rail 90, while the turntable 76 is formed with a circular base 92 having an annular surface 94 corresponding to and adapted to ride on the circular rail. The turntable 76 also is formed with an. annular flange 96 which encompasses the circular rail 90 and provides a seal or protection against ingress of dust or other foreign material between the circular base 92 of the turntable 76 and the turntable bed.

A headed pivot pin 110, in the form of a shoulder bolt, extends through and is secured to the carriage 70 centrally of the circular rail 90 thereof, as by a nut .112, and passesthrough bosses 114 and 116 provided on the carriage 70 and on the turntable 76 respectively. The pivot pin 110 serves to center the turntable 76 on the circular rail 90 while permitting turning movement of the turntable about the axis of the pivot pin, which is the turntable axis.

The turntable 76 includes an upstanding body 100 having a pair of transversely spaced bearings 98 formed therein, each of which preferably consists of longitudinally spaced portions 98a and 98b formed in the forward and rear wall members of the upstanding body respectively.

A workpiece holder 120 is removably mounted on th turntable 76, and includes a holder base 122 comprising a substantially flat shelf 124 having a pair of cylindrical sockets 126 in its forward face 121. The sockets have parallel axes, and are spaced apart transversely to correspond with the bearings 98 in the turntable. The sockets 126 are adapted to receiverespectively, corresponding ends of two elongate guide rods 130 which are fixed to the shelf 124, as by set screws 128, when seated in the sockets. When thus seated, theguide rods extend forwardly of the holder base, and are adapted to be received in the bearings 98 in the turntable body 100.

1 The holder base 122 carries a projection 132 (Figs. 4

and 6) extending from its forward face 121 positioned to abut the head 11% of the turntable pivot pin 110 when the guide rods are projected through the bearings 93. The guide rods are of such length that their forward ends 131 project slightly from the turntable body when the guide rods are inserted through the bearings until the projection 13?. of the holder base abuts the head of the turntable pivot pin.

A keeper bar 134 (Fig. 2) is provided as a means for preventing the guide rods and the holder base from sliding relative to the turntable. The keeper bar substantially takes the shape of a truncated T, and has arms 136 adapted to enter annular grooves 138, one in the projecting forward end 131 of each guide rod 130. A thumb screw 140 is threaded through the keeper bar 134 intermediate the two arms 136 to bear against the forward wall of the turntable body. The force exerted by the thumb screw 140 against the keeper bar 134 and the turntable body forward wall firmly seats the projection 132 of the holder base in abutting relationship with the head 118 of the turntable pivot pin 110.

The holder base shelf 124 has an arm 142 (Figs. and 6) extending laterally therefrom upon which a pivot assembly 144 is adjustably positionable. The arm is provided with an elongate slot 146 extending transversely of the axes of the guide rods, the slot being positioned such that its extended center line intersects the turntable pivot axis. The length of the slot and its lateral location relative to the turntable pivot axis are such as to permit adjustment of the position of the pivot assembly 144 throughout the entire range of movement required to accommodate in the workpiece holder. the standard range of sizes of brake shoes. The workpiece holder simulates-the actual brake assembly in respect to the relative locations of the brake drum center and the fixed anchor for the shoe. A shallow elongate channel 148 concentrically overlies the slot 146 and is of greater length and width than the latter for reasons hereinafter explained.

The pivot assembly 144 (Fig. 7) includes a cylindrical bushing 150 having a hexagonal flange 152 on the upper end thereof. This bushing is disposed vertically in the slot 146 with the hexagonal flange seating in the channel 148 as to be slidable therein along the length of the channel due tothe engagement of two opposed segments 153 of the flange with the upstanding sides of the channel. When the hexagonal flange is properly seated in the channel, the axis, of the cylindrical bushing 150 will be parallel to the turntable pivot axis, while a plane containing both axes will be perpendicular to the axes of the guide rods. "lhe bushing 150 is of sufficient length to project through the slot 146, and is adapted to be firmly fastened in any desired position of ad ustment along the length of the slot by a nut 153 and washer 154, the former being threaded onto the bushing. The bushing contains an axial cylindrical bore 155 within which an anchor pm 156 is slidably and pivotally recelved. The anchor pin has an enlarged head 158 which has a diameter adapted to be received firmly in the anchor guide recess of the brake shoe to be ground, in order to permit accurate positioning of the shoe in the grinding device. in this connection, an anchor pin head .810 inches in diameter will fit the most commonly used brake shoe. However, brake shoes are used which have recesses adapted to accommodate larger anchors. In or der to correctly position such a recess about an undersized anchor pin head, the anchor pin may be modified to provide a symmetrical base for the recesses. Accordingly, a generally rearward facing vertical fiat 300 is formed on the anchor pin head 301, this flat extending longitudinally of the cylindrical pin head to provide two sharp vertical edges against which the arcuate anchor guide recess can be firmly seated as shown in Fig. 9. in order to properly center the recess about the anchor pin, the flat is located such that a radius of the arcuate recess which bisects that recess will lie substantially in a plane extending radially from the cylindrical anchor pin head perpendicularly to the flat. If the recess is either too small for the anchor pin head or is so oversize that the vertical flat will not provide a firm seat therefor, it will be necessary to replace the anchor pin with one having a head of correct diameter.

A workpiece chuck 160 (see Fig. 4) is supported on the holder base for sliding movement relative thereto, and includes a frame 162 having a generally U shape, with the U disposed on its side, extending transversely of the device, and opening toward the grinding element. As thus disposed, the frame has upper and lower horizontal members or

arms

164 and 166. A pair of bosses 168 (Fig. 3) project from the upper surface of the upper member 164 and are spaced apart transversely, the bosses bearing cylindrical bores 169 vertically therethrough in which a pair of identical thrust pins 170 (Fig. 3) are slidably disposed. A pair of workpiece locater buttons 172, in the form of beaded pins, project slightly from the upper face of the lower member 166, these pins being concentric with the thrust pins 170. Overlying the two thrust pins-is a cap 174 which is provided with a recess 179 on its lower face into which are received the upper ends of the thrust pins. Means for attaching the cap to the frame are provided in the form of a threaded stud 173 paralleling the thrust pins and slidably projecting through the cap into threaded engagement with a boss 171 formed on the upper member of the frame 162 intermediate of the bosses 168. The stud carries a manipulating knob 175 at its upper end to facilitate the advance or retraction of the threaded perv.

. 3' tion thereof. Disposed het-ween'the cap'and the-bosses 168 of the frame and on the portions of the thrust pins 170 therebetwe'en, are a'p'airof helical 'springs176. These springs abut the upper surface of the bosses at "one end thereof and abut split Washers 1'77 fastened to the upper portions of the thrust pins at the other ends of saidsp'rings suchthat anyforce tending to'propelthe'thrust'pins downw'ardlyithrbughthe cylindrical bores inthe upper member of the frame is resisted by the springs. It will be seen that a'tu'r'n'ing of the manipulating knob will thread the stud intoth'e'frame andcause the cap to force the thrust pins downwardly toward "the lo'c'a-ter' buttons. A workpiece, 'sucha's 'a'n automotive brak'e shoe BS, can befirm- 1y held inthe chuck by tightening the manipulating knob to'the point where the werkpie'ce is gripped 'between' the thrust pin'sand the locatrbutto r'fs.

Provision is 'rnad'e'torattachi'ng theehu'ck 160'to the holder base shelf 124 for relative sliding movement thereb'e'tween, including an elongate slot 125 formed longit'u'dii'ia'llyin the shelf, 'the 'c'eritf line thereof extending substantially parallel to and intefine'diate the g'uide'rods 130'. A (Sap screv'v 127 of sha'nk diameter substantially less than the width of the'slot 12'5, forreasons hereinafter set forth, is projected 've'r' ieallyupward through the latter 'and'thre'ade'd into the chuck. A Washer 129 is disposed betweefi -the head '133' of the cap screw and the bottofii or the'holderhasie shlf toprvrit the head or the cap screw'rroni assing into" or up through the slot. A spacer in the form of 'a'bushirig"123"of -a length slightly in' excess or the thickness 'dfnie shlfis' telescoped over the shank portion of the" cap screw. Theexternardiameter of this bushing also is substantially smaller 'than'the width of'the slot 125 for reasons explained hereinafter, while the length of the' bushing permits theca s rew to chuck 160 with the anchor pin 156'on'the holder base arm 142. The pivot arm'is rigidly fixed at one end, as by a set secr' ew20'3ywithin 'acyliridricalsocket 202 in thechu'ck, and at the'other end slidably' projects through a bore 204 in the head 158 of the anchorpin. A "clamp screw 206 is threaded into the anchor pi'n axially thereof to bear against the pivot arm portion disposed within the bore, and provides a means whereby the pivot arm can be released so'as to be slidable withinthe bore for adjustment of theetfecti've length thereof, and then firmly secured in that adjusted position. To provide a firm'seating of the clamp screw against the pivot arm, the pivot arm has a flattened portion 201 against which the clamp screw can bear. Once the clamp screw isfirmly screwed down against the pivot arm, the chuck'160 is secused to the holder base 122 for pivotal movement about the anchor pin 156. It can beseen that the pivot arm extending from the chuck serves to support the anchor pin against any movement axially of bushing 150.

The extent of pivotal'movementof the chuck on the holder base is limitedby the length and width of'the longitudinal elongate slot 125 in the holder base shelf 124, for it can be seen that thebushing-surrounded cap screw 12'? can travel only the arcuate path from one face of the slot 125 generally diagonally, relative to its center line, to the other face. It is for the purpose of permitting the dlagonal movement of the bushing-surrounded cap screw across the width of the slot that the cap screw 127 and the bushing 123 are of diameter substantially less than the width of the slot.

Means are provided for attaching a feed screw 180 (Figs. 1 and 4) to the'chuck, and take theform of a projection 182 extending from the forward wall thereof'and having a transverse recess 184'. The feed screw comprises an elongate rod 19'2'terminating' in a substantially ball-shaped rearmost end portion 186, with an annular reces's formed in the rod adjacent and forwardly of the ball portion. The ball portion 186 of the rod is disposed within'the transverse recess 184 of the projection 182 and is retained in that recess by an overlying retaining block 194 fastened to the frame of the chuck by cap screws 196". When the block 194 is in position, the rod is restrained against longitudinal or axial movement by a li'p 185 of the recess.

'The feed screw 180 extends forwardly of the chuck 160 to overlie the forward end of the carriage 70, and is provided with threads 208 throughout the major portiorr ot it's length. A handle 210 is secured on the forward end of the feed screw 180 in order that an operator may impart rotational movements to the feed screw and also to oscillate the same, as well as the turntable, from side to side. The threaded portion 208 is adapted to be received in a half-nut 212pr'ovided on the turntable 76 having a pair of upstanding ears 214 which define thereb'etwe'en a semi-circular'threaded bore 216, the threads of which are designed for cooperation with the threads 208 on the feed screw 180.

A'guid'e arch228 (Figs. 3 and 4) in the shape of an inverted U upstanding from the holder base 122 straddles the feed screw adjacent the 'ball portion 186, and serves the dual purpose of limiting'the movement of the feed screw to a pivoting movement in substantially a vertical plane, and of rigidly'binding the feed screw against transverse movement when the latter'is depressed into threaded engagement with the half-nut 212. To this latter end, a spring-loaded, headed thrust pin 230 is received transversely through a first arm 232 (Fig. 3) of the guide arch 228 and in a countersunk bore 234 therethrough. A hollow plug 236 is threaded into-the major opening 235 of the countersunk bore, and has an internal recess 238 in which is located a helical spring 239 compressed therein and'against the'pin 230 to project the latter within the guide arch. The spring-loaded pin 230 is positioned to bear transversely against the feed screw 180 when the latter is in depressed, thread-engaged position Within the half-nut 212, and serves to bias the feed screw against an opposing elongate boss 240 projecting within the guide arch from the second arm 242 thereof. The boss is of sufficient length in a direction parallel to the axes of the guide rods 1350 to provide a flat surface imparting to the feed screw a corresponding parallelism with the guide rod axes. The elongate boss 240, therefore, constitutes means'for maintaining the threaded portion of the feed screw 180 in vertical alignment with the half-nut 212so that upon angular depression of the feed screw in any position of the turntable the threaded portion 208 will fall into register automatically with the half-nut 2 12.

Since'the feed screw 180,-byvirtue of its reception in the recess 184 and withinthe guide arch 228 is pivoted for movement substantially in a vertical plane, it will be seen that'the operator may at will lift the feed screw out of the half-nut structure to disengage the same therefrom and by applying a thrust or a pull to the feed screw 180, as the casemay be, slide the chuck arcuately relative to the'holder base about the anchor pin 156 in a direction toward and away from the grinding element 47. Such a'sliding movement of the chuck'by the application of a thrust or a pull to the feed screw provides a fast or a coarse adjustment for the purpose of advancing a brake'shoe into initial grinding relation with respect to the grinding element. When the lining of the brake shoe has been brought into close proximity to the surface of the grinding element 47, a fine adjustment may be made by lowering the feed screw 1S0 into'the half-nut '212for engagement between the threads thereof with the threads 208 on the feedserew, after which rotation of the feed sc'r'ew about its longitudinal axis in one direction or the other will feed the chuck 160, together with the brake sho'esupported thereon, toward the grinding element for grinding purposes.

shoe.

Means are provided for locating the pivot assembly 144, and therefore the anchor pin 156, a predetermined distance from the axis of the turntable pivot pin 110 along the slot 146, and for positioning the pivot arm 200 on the anchor pin to establish a predetermined effective length of the pivot arm on which the chuck 160 will pivot about the anchor pin (see Figs. 3 and 6). These means include a first reference pin 246 fixedly upstanding from the holder base arm 142, and a gauge 248 of predetermined shape for each given size and type of brake The first reference pin is centered on the extended center line of the slot 146, and provides a convenient reference point fixed relative to the turntable pivot axis. The gauge 248 (Fig. 8) has a:first cylindrical bore 250 on a first end 245 adapted to receive therethrough the head 247 of the first reference pin 246 and seats itself on 156 is adjusted to a position in the slot 146 wherein the a head 158 isin register with the second bore 252 in the gauge 248. A shoulder 253 of height equal to that of the shoulder 249 on the first reference pin head 247 is provided on the anchor pin head 158 for seating the gauge 248.' The gauge 248 thus provides a means by which the anchorpin 156 is easilylocated in a predetermined position relative to the turntable pivot axis. Once the gauge is seated on both the first reference pin and the anchor pin head 158, the anchor pin may be firmly fastened in place by a tightening of the nut 153 on the bushing 150.

The gauge 248, when seated on both the first reference pin 246 and the anchor pin head 158, serves also to establish a predetermined effective length for the pivot arm 200, in that the other end 251 of the gauge extends beyond the second bore 252 a predetermined distance. This end 251 is of substantial width to provide an abutment edge 255 against which is seated a second reference pin 260 fixedly upstanding from the end of the pivot arm 200. Since the chuck is positioned rearwardly of the turntable axis, and the anchor pinv is positioned transversely thereof, the pivot arm 200 joining the chuck and anchor pin takes an angular direction relativeto both the longitudinal and transverse extents of the device. Accordingly, the abutment end 251 of the gauge 248 may be angularly disposed from the center line direction between the bores 258 and 252. When the second reference pin 260 and the end 251 of the gauge 248 are in contact, and the gauge is otherwise properly seated, on the first reference pin and the anchor pin head, the pivot arm 200 will have a predetermined effective length between the anchor. pin 156 and the chuck 160. Brake drumsmay have varying radii of curvature, and the assemblies therefor may havefixed anchors positioned difierently from one another relativeto their spindles, Accordingly, a different gauge is provided for the shoe of each differently dimensioned and designed assembly, each gauge having apredetermined length between centers of the first reference and the anchor pin bores. The bore-to-bore length is predetermined for each different brake drum so that the total of that length and the distance between the turntable pivot axis and the first reference bore is equal to the distance between the fixed anchor and the spindle of the brake drum whose shoe is to be processed. Theuse of a first reference pin and an elongate anchor pin slot extending radially from the turntable pivot axis thus facilitates the positioning of the anchor pin on the holder base arm.

Referring now to Fig. 6, it will be clear that once the anchor pin is positioned on the holder base arm, the pivotal position for a brake shoe relative to the turntable is also fixed. Adjustment of the effective length of the pivot arm positions the chuck so that it may receive and hold a brake shoe of any radius of curvature in operat ng proximity to the grinding element and substantially symmetrically thereto. Additionally, the force exerted be tween the grinding element and the brake shoe is borne by the chuck, which firmly holds the brake shoe against slipping, chattering or erratic movement while the shoe is in contact with the grinding element.

The lengths of the two elongate slots 146 and (see Fig. 6) limit the range of sizes of brake shoes that can be received by the device, but the slots and the gauge means for positioning the anchor pin relative to the turntable axis as well as for establishing a predetermined effective length of the pivot arm on that anchor pin are adapted to enable processing of all standard sizes of brake shoes.

A projection 178 (Figs. 5 and 6) is provided on the rearward face of each of the

frame members

164 and 166, these projections extending "rearwardly of the chuck frame to provide two seats in a perpendicular plane against which the rim of a workpiece, such as an automotive brake shoe, is positioned, while the ancho'r'pin head 158 provides a third seat for the brakeshoe. These three seats are reference points establishing a very positive and firm means of positioning a brake shoe workpiece in the grinding device.

To illustrate the operation of the device in dressing down the lining L of a standard fixed anchor brake shoe BS it may be assumed that a brake shoe is being processed for an ll-inch brake drum in new condition. Accordingly, it is necessary that an accurate 5 /2 inch pivot radius be set for the turntable in order to grind the lining L to a true are matching that of the brake drum. In order to set the arcuate radius, the operator must first free the carriage 70 for sliding movement longitudinally on the base 10. This is accomplished by the release of the clamp means thrust pin 82, and by the lateral retraction of the knob 60 from locking engagement with the indexing mechanism (not shown). The determination of the location in which the carriage is positioned on the base the correct distance from the grinding element is accomplished by use of the reference mark 66 and the scale 69 on the base. When the mark is in register with the desired indicium, "11 in the present illustration, the knob 60 is depressed to index-lock the carriage on the base. A 5 /2 inch pivot radius for the surface" of the lining L has thus been set, and no movement of the adjusting screw 62 off its zero point should be made for the brake shoe of this illustration since its brake drum is an accurate 11 inches in diameter. The carriage-indexing and adjusting mechanism is next protected from receiving the forces developed during the grinding by actuating the clamp means thrust pin 82 to frictionally lock the carriage onto the base at the correctly established location. These clamp means will thereafter receive any forces developed during the grinding operation, rather than the indexing means or the adjusting screw.'

The correct locating of the pivot assembly 144 on the arm of the holder baseis accomplished by means of a selected gauge 248 corresponding to the particular brake shoe to be ground. The pivot assembly 144 is released for sliding movement on the arm by loosening the nut 153 from the bushing 150. Thereupon the gauge 248 is placed on the first reference pin 246 so that the latter pin penetrates the bore 250 and the gauge seats itself on the shoulder 249 of the pin. The pivot assembly is moved along the slot 146 until the anchor pin head 158 c is in register with and penetrates the second bore 252 in the gauge. Once the gauge is seated on both the shoulder 249 of the first reference pin and the shoulder 253 of the anchor pin head 158, the nut 153 is tightened on the bushing to fasten the pivot assembly firmly on the holder base arm.

The effective length of the pivot arm 200 is properly set for the particular brake shoe to be ground by backing off the clamp'screw 206 from contact with the planar surface 201 of the pivot arm, and by sliding the pivot arm within the'cylindriqal bore 204 in th anchor pin 11 head until the second reference pin 260 abuts the end 251 of the gauge 248. When the pivot arm is so positioned, it is firmly fixed relative to the anchor pin by tightening down the clamp screw 206.

The chuck 168 is prepared for the brake shoe to be ground by backing off the thrust pins 170 from the locater buttons 172. This is accomplished by rotation of the manipulating knob 175, and therefore the stud 173, to effect a raising of the cap 174. This, in turn, permits the helical springs 176 to withdraw the thrust pins away from the workpiece locater buttons. When the thrust pins are sufficiently removed from the workpiece locater buttons, the brakeshoe to be ground is inserted therebetween until the rim R of the brake shoe abuts both of the projections 178 of the chuck 160 and the anchor recess AR accommodates the anchor pin head 158. The brake shoe is fastened in this position by screwing the stud 173 further into the frame 162 until the thrust pins 170 firmly bias the flange F of the brake shoe between them and the locater buttons 172. Due to the vertical alignment of both projections 178, one with the other,

and the horizontal alignment of both locater buttons 172 one with the other, the brake shoe is seated as to have its pivot axis correctly disposed parallel to the axis of the grinding wheel.

The brake shoe is brought into close proximity to the grinding wheel rapidly by the coarse advancing means. This is accomplished by swinging the feed screw 180 upwardly out of engagement with the half nut 214, whereupon a forward thrust on the feed screw will cause the workpiece chuck 160, together with the brake shoe that it holds, to move toward the grinding element pivotally about the anchor pin 156. When the surface of the lining L is in close proximity with the grinding element, the accurate advancing-means are employed to complete the advance of the workpiece into the grinding element. This is accomplished by depressing the feed screw 180 pivotally about its ball portion 186 to cause its threaded portion 208 to engage the threads 216 in the half-nut 214. The feed screw 180 is then firmly held between the halfnut 214 and the guide arch 228, and by its rotation about its longitudinal axis advances the chuck 160 in a finely controlled manner by means of the threaded engagement between the feed screw and the half-nut 214. Inasmuch as the radius of curvature of the arcuate surface to be processed is fixed by the location of the turntable axis and corresponds to the distance between the turntable axis and the closest point thereto on the grinding wheel, the brake shoe is advanced into the grinding wheel until the entire arcuate extent of the lining L will be dressed down upon oscillation of the entire turntable, workpiece holder assembly, and brake shoe as a unit, by oscillatory manipulation of the handle 219.

When a brake drum has been machined to either remove scorings on the inner surface thereof or to bring the inner surface thereof to a true circular shape, the drum will no longer have a diameter of standard whole-inches dimension, such as, for example, 11 inches. The present device is equally well adapted to process the lining of the brake shoe for this enlarged brake drum, the only additional adjustment necessary being that of advancing the adjusting screw so that the turntable radius established between the turntable axis and the surface of the grinding wheel is increased by the difference between the initial or standard radius of the brake drum and its rebored radius. Since the position of the fixed anchor in the brake drum relative to the drum spindle is the same as in the drum when in new condition, no adjustment of the anchor pin on the holder base arm need be made, and the brake shoe can be ground as heretofore described in connection with a brake shoe for a new or standard size brake drum.

'While the present invention is particularly well-adapted to and has been described in connection with grinding linings of brake shoes of the fixed anchor type, the invention is not limited to such a use, for a grinding device incorporating the principles of this invention can accommodate equally well brake shoes of the adjustable anchor type. As when dressing down the linings of a fixed anchor brake shoe, a gauge 248 must be selected for use, which corresponds to the particular brake shoe to be ground. An adjustable anchor shoe is positioned in the chuck in the same manner as a fixed anchor shoe, utilizing the projections 178 of the chuck 160 and the anchor pin head as reference seats for the shoe rim and the brake shoe anchor recess. The shoe is pivotally advanced in the manner of fixed anchor shoes toward the grinding element, and swung through an arc of engagement therewith. It can be seen that the capability of this grinding device of processing both types of brake shoes, adds considerably to the chiciency and convenience of its use, particularly in the herein discussed automotive brake shoe field.

It can be seen that the present invention substantially duplicates the brake drum for a fixed anchor brake shoe being ground. The turntable pivot axis and the workpiece holder anchor pin correspond respectively to the drum spindle and the drum anchor. The grinding element edge closest to the turntable pivot axis corresponds to a line on the drum braking surface, while the circular extent of that drum surface is duplicated, not by rotation of the grinding element edge around the turntable and about the turntable pivot axis, but rather by rotation of the turntable, with its supported workpiece holder and brake shoe, about the turntable pivot axis. The contour of the drum surface is represented by the path the closest edge of the grinding element describes relative to the turntable periphery. It can be further seen that as the shoe is advanced pivotally into that path, the lining of the shoe will be ground to the contour of the brake drum.

The elongate slot 146 in which the anchor pin is slidably positionable extends transversely of the axes of the guide rods 131, and therefore the anchor pin is always located laterally from the axial direction of the application of force by the feed screw 180. Such a structure makes possible the advance of the shoe pivotally about the anchor pin by the application of a feed screw force in substantially the same manner as a braking force pivots the shoe within the drum therefor. The combination of the elongate transverse slot and the first reference pin a fixed distance from the turntable pivot axis provides a novel and convenient means of locating the anchor pin a predetermined distance from the turntable pivot axis, and enables the use of a gauge 248 convenient for that purpose.

The elongate slot extending longitudinally relative to the turntable makes possible not only the arcuate movement of the chuck cap screw 127 therein as the chuck and workpiece are pivoted about the anchor pin, but also the longitudinal adjustment of the chuck and workpiece toward or away from the grinding element as the effective length of the pivot arm 200 is lengthened or shortened. The proper position of the chuck relative to the grinding element is dependent on whether the workpiece is of relatively large or small radius of curvature and therefore of relatively flat or of sharp arcuate contour. It will be apparent that the surface of a workpiece of relatively fiat contour will not project from the chuck to the extent the surface of a workpiece of relatively sharp contour projects, and that the chuck for the workpiece of flat contour must itself be farther advanced to the grinding element to es tablish grinding contact between that element and the workpiece.

The bushing-surrounded chuck cap screw 127 is free to move arcuately in the longitudinal slot 125 (Fig. 6) until the bushing-surrounded cap screw abuts a face of the slot. Since the cap screw is rigidly connected to the chuck, which in turn firmly holds a brake shoe BS, it can be seen that any advancing movement of the cap screw 127 is attended by movement of the brake shoe. The brake shoe is preferably advanced to a position where the lining L of the shoe will be in engagement with the grinding element throughout the entire extent of the lining when the brake shoe is pivoted with the turntable. When the brake shoe is pivoted with the turntable and in contact with the grinding element, material will be ground from the lining tapering from a greatest depth of removal in an area generally intermediate of the lining ends toward areas of least depth of removal adjacent those ends.

The pivot arm 200 is made to be slidably positionable on the anchor pin to provide adjustment of the efiective length of the former. This adjustment is required to accommodate the shoes for drums of varying diameters, for it can be seen that as the distance from the turntable pivot axis to the grinding element is increased to simulate larger diameter drums, and as the anchor pin is positioned laterally farther from the turntable pivot axis to simulate the position of the anchor in the larger drums, so also must the pivot arm, corresponding to a hypotenuse of these two lengths, be increased to correctly position the chuck and workpiece relative to the grinding element.

It will be apparent that this device is simple in construction and can be economically manufactured. At the same time, however, the device is rugged and sturdy, free from any requirement of delicate adjustment, and free from easily broken or deformed parts which might require replacement.

I claim:

1. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base rigidly mounted on the turntable, an arm extending laterally from said holder base, an anchor pin on said arm, a workpiece chuck slidably mounted on said holder base for arcuate movement relative thereto about said anchor pin toward and away from the grinding element, and a pivot arm connecting said chuck and said anchor pin.

2. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base rigidly mounted on the turntable, an anchor pin upstanding from said holder base, a workpiece chuck, a pivot arm connecting said chuck and said anchor pin, and means slidably mounting said chuck on said holder base for arcuate movement of said chuck relative to said holder base toward and away from the grinding element, said mounting means including an elongate slot in said holder base extending generally toward and away from said grinding element, a screw projected through said slot and threaded into said chuck, and a cylindrical spacer on said screw, said spacer being of substantially smaller external diameter than the width of said slot.

3. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base rigidly mounted on the turntable, an arm extending laterally from said holder base, an anchor pin positionable in a plurality of locations on said arm, a workpiece chuck slidably mounted .on said holder base for arcuate movement relative thereto about said anchor pin toward and away from the grinding element, a pivot arm connecting said chuck and said anchor pin, and means for adjusting the efiective length of said pivot arm.

4. A workpiece holder for a grinder of the type having a base, a grinding element rotatably mounted on the base, a carriage mounted on the base for sliding move- I ment toward and away from the grinding element, and

a turntable carrying an open half-nut and rotatably mounted on the carriage on a pivot axis parallel with the axis of rotation of the grinding element, said workpiece holder comprising a holder base rigidly mounted on the turntable, an anchor pin upstanding from said holder base, a workpiece chuck slidably mounted on said holder base for arcuate movement relative thereto about said anchor pin toward and away from the grinding element, a pivot arm connecting said chuck and said anchor pin, and a feed screw attached to said chuck rotatably relative thereto and swingably relative thereto into and out of threaded engagement with the half-nut, said feed screw constituting a thrust rod for manual movement of said chuck relative to said holder base when said feed screw is disengaged from the half-nut and constituting screw means for accurate movement of said chuck relative to said holder base upon rotation of the feed screw when the latter is in threaded engagement with the half-nut.

5. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable carrying an open half-nut and rotatably mounted on said carriage, said workpiece holder comprising a holder base rigidly mounted on said turntable, an anchor pin upstanding from said holder base, a workpiece chuck slidably mounted on said holder base for arcuate movement relative thereto about said anchor pin toward and away from the grinding element, a pivot arm connecting said chuck and said anchor pin, a feed screw attached to said chuck as to be rotatable relative thereto and swingable relative thereto into and out of threaded engagement with the half-nut, and a guide arch upstanding from said holder base and straddling said feed screw, said feed screw constituting a thrust rod for manual movement of said chuck on said holder base when said feed screw is disengaged from the half-nut and constituting screw means for accurate movement of said chuck on said holder base upon rotation of said feed screw when the latter is in threaded engagement with the half-nut, said guide arch holding said feed screw against transverse movement when the latter is in engagement with the halfnut and vertically aligning said feed screw with the halfnut when the feed screw is depressed toward threaded engagement therewith.

6. A workpiece holder for a grinder of the type having a base, a grinding element rotatably mounted on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage on a pivot axes parallel with the axis of rotation of the grinding element, said workpiece holder comprising a holder base rigidly mounted on the turntable, an anchor pin upstanding from said holder base, a workpiece chuck slidably mounted on said holder base for arcuate movement relative thereto about said anchor pin toward and away from the grinding element, a pivot arm connecting said chuck and said anchor pin, a feed screw having a ball-like end portion, and means rotatably and swingably attaching said feed screw to said chuck, said attaching means including a projection extending from said chuck, a recess in said projection for receiving said ball-like end portion, and a retaining block fixed to said chuck and holding said ball-like end portion in said recess, said feed screw constituting a thrust rod for manual movement of said chuck relative to said holder base when said feed screw is disengaged from the half-nut and constituting screw means for accurate movement of said chuck relative to said holder base upon rotation of the feed screw when it is in threaded engagement with the half nut. 7. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding mo ement toward and away from the grinding element, and a turntable rotatably mounted on the carriage and containing a pair of transversely spaced cylindrical bores, said workpiece holder comprising a holder base, means removably mounting said holder base on the turntable, said mounting means including a pair of transversely spaced longitudinally extending guide rods projecting from said holder base and slidably received in the turntable bores, and means for rigidly clamping said guide rods in the bores, an anchor pin upstanding from said holder base, a workpiece chuck slidably mounted on said holder base for arcuate movement relative thereto about said anchor pin toward and away from said grinding element, and a pivot arm connecting said chuck and said anchor pin.

8. The invention of claim 7 wherein said guide rods project through said bores forwardly of said turntable, and said means rigidly clamping said guide rods in the bores include an arcuate groove in the projecting end of each of said guide rods, a keeper bar engaging both of said arcuate grooves, and means acting between said keeper bar and the turntable for holding the guide rods against axial movement relative to the turntable.

9. A workpiece holder for a brake shoe grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base mounted on the turntable, an anchor pin upstanding from said holder base, a workpiece chuck slidably mounted on said holder base for arcuate movement relative thereto about said anchor pin toward and away from the grinding element, and a pivot arm connecting said chuck and said anchor pin, said workpiece chuck including a frame, a pair of transversely spaced pads fixedly supported by said frame and having brake shoe flange-engaging surfaces lying in a plane and disposed to engage one face of the flange of a brake shoe in the holder, a pair of pins slidably projectable through said frame in register with said pads and into abutment with the other face of the flange of the brake shoe in the holder, a cap overlying both of said pins, a stud projected through said cap intermediate of said pins and threaded into said frame, a manipulating knob on the end of said stud, and spring means urging said pins away from said pads.

10. A workpiece holder for a brake shoe grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and

a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base mounted on the turntable, an anchor pin upstanding from said holder base, a workpiece chuck slidably mounted on said holder base for arcuate movement relative thereto about said anchor pin toward and away from the grinding element, and a pivot arm connecting said chuck and said anchor pin, said workpiece chuck including a frame, a pair of transversely spaced pads fixedly supported by said frame and having brake shoe flange-engaging surfaces lying in a plane and disposed to engage one face of the flange of a brake shoe in the holder, a pair of pins slidably projectable through said frame in register with said pads and into abutment with the other face of the flange of the brake shoe ,in the holder, a cap overlying both of said pins, a stud projected through said cap intermediate of said pins and threaded into said frame, a manipulating knob on the end of said stud, spring means urging said pins away from said pads, and a brake shoe rim-engaging abutment projecting from said frame toward the grinding element.

11. A workpiece holder for a brake shoe grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base mounted on the turntable, an anchor pin upstanding from said holder base, a workpiece chuck slidably mounted on said holder base for arcuate movement relative thereto about said anchor pin toward and away from the grinding element, and a pivot arm connecting said chuck and said anchor pin, said workpiece chuck including a frame, a pair of transversely spaced pads fixedly supported by said frame and having brake shoe flange-engaging surfaces lying in a plane and disposed to engage one face of the flange of a brake shoe in the holder, a pair of pins slidably projectable through said frame in register with said pads and into abutment with the other face of the flange of the brake shoe in the holder, a cap overlying both of said pins, a stud projected through said cap intermediate of said pins and threaded into said frame, a manipulating knob on the end of said stub, spring means urging said pins away from said pads, and a pair of vertically spaced abutments projecting from said frame toward the grinding element and having brake shoe rim-engaging surfaces lying in a plane perpendicular to the flange-engaging surfaces of said pads.

12. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base rigidly mounted on the turntable, an anchor pin positionable in a plurality of locations on said holder base along a line perpendicular to the line of movement of the carriage and passing through the axis of rotation of the turntable, a workpiece chuck slidably mounted on said holder base for arcuate movement relatively thereto about said anchor pin toward and away from the grinding element, a pivot arm connecting said chuck and said anchor pin, and means for positioning said anchor pin in any of its said locations on said holder base and for adjusting the effective length of said pivot arm.

13. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base rigidly mounted on the turntable, an anchor pin assembly positionable in a plurality of locations on said holder base, a workpiece chuck slidably mounted on said holder base for arcuate movement relatively thereto about said anchor pin assembly toward and away from the grinding element, a pivot arm connecting said chuck and said anchor pin assembly, and means for positioning said anchor pin assembly in a predetermined location on said holder base and for adjusting the effective length of said pivot arm, said means including an elongate slot in the holder base for guiding the movement of said anchor pin assembly, said anchor pin assembly including a headed and threaded cylindrical bushing slidably projected through said slot, a nut holding said bushing in said slot, an anchor pin slidably carried within said bushing, an enlarged head on said anchor pin, a transverse cylindrical bore in said head for slidably accommodating said pivot arm, said pivot arm supporting the anchor pin against axial movement within said bushing, and means for releasably fastening said pivot arm to said anchor pin head.

14. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base rigidly mounted on the turntable, an anchor pin assembly positionable in a plurality of locations on said holder base, a workpiece chuck slidably mounted on said holder base for arcuate movement relatively thereto about said anchor pin assembly toward and away from the grinding element, a pivot arm connecting said chuck and said anchor pin assembly, and means for positioning said anchor pin assembly in a predetermined location on said holder base and for adjusting the effective length of said pivot arm, said means including an elongate slot in the holder base for guiding the movement of said anchor pin assembly and a shallow channel concentrically overlying said slot, said anchor pin assembly including a threaded cylindrical bushing, a polygonal head on said bushing, said bushing projecting through said slot and said polygonal head slidably supported within said channel, a nut threaded on said bushing to hold said bushing in said slot, an anchor pin slidably carried within said bushing, an enlarged head on said anchor pin, a transverse cylindrical bore in said anchor pin head for slidably accommodating the pivot arm, said pivot arm supporting the anchor pin against axial movement within said bushing, and means for releasably fastening said pivot arm to said anchor pin head.

15. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base rigidly mounted on the turntable, an anchor pin slidably adjustable on said holder base along a line perpendicular to the line of movement of said carriage and passing through the axis of rotation of the turntable, a workpiece chuck slidably mounted on said holder base for arcuate movement relative thereto about said anchor pin toward and away from the grinding element, a pivot arm fixed at one end to said chuck and slidably carried by said anchor pin at another end, means for positioning said anchor pin in any of its said locations on said holder base and for positioning said pivot arm on said anchor pin, said means establishing a predetermined radius of and positioning the center for the arcuate movement of said chuck.

16. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable mounted on the carriage and rotatable about an axis, said workpiece holder comprising a holder base rigidly mounted on the turntable, an anchor pin positionable in a plurality of locations on said holder base, a workpiece chuck slidably mounted on said holder base for arcuate movement relatively thereto about said anchor pin toward and away from the grinding element, a pivot arm connecting said chuck and said anchor pin, and means for establishing a predetermined radius of and positioning the center for the arcuate movement of said chuck, said means including a gauge positioning said anchor pin on said holder base a predetermined distance from said turntable axis and positioning said pivot arm on said anchor pin to establish a predetermined effective length for said pivot arm.

17. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base rigidly mounted on the turntable, an anchor pin positionable in a plurality of locations on said holder base, a workpiece chuck slidably mounted on said holder base for arcuate movement relatively thereto about said anchor pin toward and away from the grinding element, a pivot arm connecting said chuck and said anchor pin, and means for positioning said anchor pin in a predetermined location on said holder base and for adjusting the effective length of said pivot arm, said means including a first reference pin fixedly upstanding from the holder base, a second reference pin fixedly upstanding from the end of the pivot arm adjacent said anchor pin, an elongate slot in the holder base for guiding the move ment of said anchor pin, and a gauge adapted to be mounted on one end thereof on said first reference pin and to be mounted at a central portion thereof on said anchor pin when said anchor pin is moved along the slot to a predetermined distance from said first reference pin, the second end of said gauge providing an abutment for said second reference pin a predetermined distance from said anchor pin.

18. A workpiece holder for a brake shoe grinder of the type having a base, a grinding element supported on the base, a carriage mounted on the base for sliding movement toward and away from the grinding element, and a turntable rotatably mounted on the carriage, said workpiece holder comprising a holder base mounted on the turntable, an arm extending laterally from said holder base, an anchor pin positionable in a plurality of locations on said arm, said anchor pin being adapted to engage the anchor recess of a brake shoe when the latter is positioned in the holder, a workpiece chuck slidably mounted on said holder base for arcuate movement relative thereto about said anchor pin toward and away from the grinding element, a pivot arm adjustable in effective length connecting said chuck and said anchor pin, said workpiece chuck including a frame, a pair of transversely spaced pads fixedly supported by said frame and having brake shoe flange-engaging surfaces lying in a plane and disposed to engage one face of the flange of a brake shoe in the holder, a pair of pins slidably projectable through said frame in register with said pads and into abutment with the other face of the flange of a brake shoe in the holder, a cap bearing against corresponding ends of both of said pins, a stud projected through said cap intermediate of said pins and threaded into said frame, a manipulating knob on the end of said stud, spring means urging said pins away from said pads, and means for positioning said anchor pin in a predetermined location on said holder base arm and for adjusting the effective length of said pivot arm, said means including a first reference pin fixedly upstanding from said holder base arm, a second reference pin fixedly upstanding from the end of said pivot arm adjacent said anchor pin, an elongate slot in said holder base arm for guiding the movement of said anchor pin, and a gauge adapted to be mounted on one end thereof on said first reference pin and to be mounted at a central portion thereof on said anchor pin when said anchor pin is moved along the slot to a predetermined distance from said first reference pin, the second end of said gauge providing an abutment for said second reference pin a predetermined distance from said anchor pin.

19. A workpiece holder for a grinder of the type having a base, grinding element supported on the base, a carriage slidable on the base toward and away from the grinding element and a turnable mounted on the base for pivotal movement about an axis on the axis of movement of the carriage, said holder comprising a holder base rigidly secured to the turntable, a brake shoe clamp slidable in an are on said holder base in a direction toward and away from the grinding element, and adjustable means for locating the position of the center and determining the radius of movement of said clamp including a radius arm rigidly projecting from said clamp, a pin for engagement by the anchor pin recess of a brake shoe in said clamp, said pin being located on a line perpendicular to the axis of movement of said carriage and passing through the pivot axis of said turntable and adjustable along said line toward and away from the axis of said turntable and means for adjustably connecting said arm to said pin at different positions along said arm to thereby vary the effective length of said arm from said clamp to said pin.

20. A workpiece holder for a grinder of the type having a base, a grinding element supported on the base, a carriage slidable on the base toward and away from the grinding element and a turntable mounted on the base for pivotal movement about an axis on the axis of movement of the carriage, said holder comprising a holder base rigidly secured to the turntable, a brake shoe clamp slidable in an are on said holder base in a direction toward and away from the grinding element, and adustable means for locating the position of the center and determining the radius of movement of said clamp including a radius arm rigidly projecting from said clamp, 21 pin for engagement by the anchor pin recess of a brake shoe in said clamp, said pin being located on a line perpendicular to the axis of movement of said carriage and passing through the pivot axis of said turntable and adjustable along said line toward and away from the axis of said turntable, means for adjustably connecting said arm to said pin at different positions along said'arm to thereby vary the effective length of said arm from said clamp to said pin, and a gauge removably disposed on said pin and having portions extending along said perpendicular line and along the axis of said radius arm for determining the position of said pin and the effective length of said radius arm.

21. A workpiece holder for a grinder of the typehaving a base, a grinding element supported on the base, a. carriage slidable on the base toward and away from the grinding element and a turntable mounted on the base for pivotal movement about an axis on the axis of movement of the carriage, said holder comprising a holder base rigidly secured to the turntable, a brake shoe clamp slidable in an are on said holder base in a direction toward and away from the grinding element, and adjustable means for locating the position of the center and --determining the radius of movement of said clamp including a radius arm rigidly .lp'rojecting from said clamp, a pin for engagement by "the anchor pin recess of a brake shoe in said clamp, said pin being located in a line perpendicular to the axis of movement of said carriage and passing through the pivot axis of said turntable and adjustable along said line toward and away from the axis of said turntable, means for adjustably connecting said arm to said pin at different positions along said arm to thereby vary the effective length of said arm from said clamp to said pin, an abutment on said holder base between said pin and said pivot, an abutment on that portion of said arm which extends on the other side of said pin from said clamp, and a gauge removably disposed on said pin'and having a por tion abutting the abutments in said holder base and on said arm respectively for determining the position of said pin and the efiective length of said radius arm.

References Cited in the file of this patent UNITED STATES PATENTS 675,609 Pashl'ey 'June 4, 1901 1,095,338 Mallory May 5, 1914 1,287,091 Pearsen Dec. 10, 1918 2,098,267 Weihampel Nov. 9, 1937 2,289,693 Blazek July 14, 1942 2,325,826 Barrett Aug. 3, 1943 2,715,799 Billeter Aug. 19, 1950