US1772025A - Brake-drum-truing machine - Google Patents

Description

Aug- 5, 1930 H. B. BARRETT 1,772,025

BRAKE DRUM TRUING MACHINE Filed Jan. 22, 1929 3 Sheets-Sheet 1 l /O l l EL Sym Aug. 5, 1930. H. B. BARRE-rr 1,772,025

BRAKE DRUM TRUING MACHINE Filed Jan. 22, 1929 3 Sheets-Sheet 2 wfg. 559

jme/M01" #any Bar/'ett www - tta/wey Aug. 5, 1930. H. B. BARRETT 1,772,025

BRAKE DRUM TRUING MACHINE Filed Jan. 22, 1929 5 Sheets-Sheet 3 mwewg@ I @mw Hf 35 moving parts of the machine. y

It is another purpose of my invention tov i Patented Aug. 5, 1930 UNITED STATES PATENT OFFICE HARRY 1?..v BARRETT, O F Los ANGELES, CALIFORNIA, AssIGNOR To IT. B. BARRETT co., LIMITED, OF Los ANGELES, CALIFORNIA, A CORPORATION or NEVADA 4 BRAKEDRUM-TRUING MACHINE Application led .Tanuary22, 1929. Serial No. 334,315.

My invention relates to and has for a purpose the provision of a sim-ple and durable .machine by which one or more cuts can be y and infact a necessity lin order to obtain'. 1o maximum braking efficiency from the drum when in use. I v

It is a further purpose ofu iny invenftion to provide a compact and portable brake drum truing machine of Acomparatively light, weight, which, with a brake 'drum carrying wheel removed from the vehicle and resting substantially horizontally on .a support, is capable of being appliedk to and supported as 'a unit by the' wheel duringthe truing operation, and insuch manner asto insure the utmost accuracy'in truing the drum so, that the necessity for a .-large and permanently installed expensive machine will be dispensed with, and yet the t-ruing operation performed with accuracy and but aininimum expenditure of time and labor. I

It is a still further purpose of-myginven` tion to providea brake drum truing machine,

embodying means for signaling the completion Vof the truing operation and for-automatically discontinuing the'supply of power tothe machine when the tr'uing operation has been completed so as to prevent a needless consumption ,of power and wear. of the provide a brake drum truing 'machine em bodying a simple and positively acting mechanism by'which the operation of a tool feed- 40 ing carriage can be controlled to either cause a power feed of the carriage or permit a many ual feed as desired, with a means embodied in a feeding means for thecarriage by `which the feeding of the carriage will be automatically discontinued in the event that the sup-4 ply Of power to the machine be continued after a cut upon the drum has been completed, so that damage to the machine as a result of continued feeding of the carriage will be positively prevented.

I will describe only one form of brake drum truing machine embodying my invention and will then point out the novel features lthereof in claims. In the accompanying drawings,

- F1g. 1 1s a vlew showlng 1n front elevation, one form of brakedrum truing machine Y embodying my invention. .Fig 21s ag-view in side elevation ofthe machine shown in the preceding figure.

Fig. 3 is an enlarged vertical 'sectional view takenon the line 3-#3 of Fig. vl andv looking in the direction of the arrows.V

Fig. 4 is a horizontal sectional view taken on the linefl-li of Fig. 1 and looking inthe direction of the arrows.

Referring spec-ically tothedrawingsI in. l

which similar 'reference charactersI designate similar Aparts in each 'of the several views, my invention in its present embodiment comprises an4 arbor A adapted to be detachably l'secured to a conventional form of vehicle .4

wheel W carrying a brake drum D, 1n such g l mannerthat with the wheel removed fromthe vehicle and resting in -a horizontal posi-y tion on suitable supports such as a pair 'of beams B, the arbor will be supported by the wheel in axial alinement with the wheel axisl andwill extend vertically upward from the brake drum 'side of the-wheel. 'In the present instance the arboris in the form vof a shaft of `uniform diameter and is provided at its lower end with a tapered threaded' socket 10 which threadedly receives a threaded shank 11 formed on a mandrel -12 extending through the hub of'the wheel and provided with op-` positely disposed conical sleeves 13 and 14 which co-opera-te with a nut 15 threaded on the lower end of the mandrel, and one or more `washers 16 interposed between the nut and wheel hub, to center and secure the mandrel in the hub. lith the shank' 11 of the manarbor A by means of a key 17 which provides a splined connection between the arbor and carriage operating to prevent rotation of the latter on the arbor yet rendering the carriage free to travel along the arbor. A tool holder H is rotatably mounted on the arbor below the carriage C and is operatively connectedto the carriage for slidingl movement with the latter on the arbor so that in response to rotation of the holder, and with a suitable tool 18 carried by the holder, in engagement with either the inner or outer periphery of the brake drum, a cut will be taken from the drum concentric) with and parallel to the axis of the wheel, thus rendering the peripheral surface of the drum perfectly true, to insure ainaximuln braking effect from the 'drum when 1n use.

To operatively connect the A,holder H to the carrlage C for sliding movement along the arbor by the carriage while rendering the holder free to be rotated on the arbor, lne holder is provided with an axial hub 19 (Fig. 2) having an annular outwardly projecting flange 20 freely entering an axial socket 2l formed in the lower end of the carriage C. Also mounted in the socket 2l on opposite sides of the flange 20 are thrust bearings 22 and. 23; and to retain the bearings and flange against displacement from the socket, a piurality of studs 24 having lock nuts 25, are threaded radially into tne lower end of the carriage and project into the socket immediately below the lower thrust bearing l` he inner ends of the studs 24 are of conical form as indicated at 25a and engage the underside of the thrust bearing 23, so that in the event of any wear occurring on the bearings, the resulting clearance can be removed by screwing the studs inwardly of the socket, the inner conical ends 25@l forming wedges to force the bearing 23 upward in the socket.

The holder H is thus suspended from thez carriage C for sliding movement onthe arbor by the carriage; and assuming that Ithe tool 18 is taking a cut from the drum D during upwardmovement of the carriage on the arbor, the tool will be pulled upwardly by the carriage-and as a result prevent chattering of the tool on the drum.

In the present instance the tool 18 is detachably secured to a bar 26 by a set screw 27, and the bar projects at a right angle from a supporting member 28 slidably mounted in the head 29 of the tool holder at right angles to the length of the arbor and to one `side ofthe latter as clearly shown in Fig. 4.

A key 30 restricts the member 28 to sliding movement in the head; and to provide for adjustment of the tool 18 to accommodate brake drums of different sizes and depths of cuts as well as to lock the tool in a selected position of adjustment, an adjusting screw 31 having a crank handle 32 is journaled in a U shaped frame 33 secured to the head 29,

wardly of the head and will be automatically locked in a selected position of adjustment.

To provide means for rotating the tool holder H, I preferably provide an electric motor M which is supported by a bracket .34 secured to the upper end of the carriage C. To the shaft 35 of the motor is fixed a set of pulleys 36VA of respectively different diameters, over any one of which is adapted to be trained an endless belt 37 also adapted to be trained over any one of a set of pulleys 38 reversely disposed from the pulleys 36 and fixed to a drive shaft 39 journaled in spaced apart brackets 40 secured to the carriage C by studs 4l. To the drive shaft 39 between the brackets 40 is fixed a worin 42 which constantly meshes with a worm wheel 43 fixed to the hub 19 of the tool holder H so that with the motor M in operation the holder will bc rotated on the arbor, and by shifting the position of the belt 37 on the sets of pulleys 36 and 38 the speed of rotation of the holder and hence the tool 18 can be varied.

As the holder is rotated, the carriage C is adapted to be simultaneously fed ulnwardlyv on the arbor A, so as to feed the tool 1S upwardly across the periphery of the drum D; and to this end a second worm wheel 44, constantly meshing with the worm 42 at the opposite side of the latter, is fixed to a shaft 45 journaled vertically in an arm 46, pivoted between the brackets 40 on a pin 47, and having fixed thereto at its upper end, a second worm 48 meshing with a third worm wheel 49 fixed to a stub shaft 50 journaled in a pair of spaced apart brackets 5l secured to the carriage C. Also fixed to the stub shaft 50 is a bevel gear 52 constantly meshing with a similar bevel gear 53 fixed to a feed screw 54 ournaliel vertically at its lower end in a socket 55 against upward endwise displacement from :the soc et by means of an abutment 56 secured fto the carriage and vabutting the hub of the 1bevel gear 53 above the latter.

The feed screw 54 threadedly engages a nut 57 in the form of an arm slidable on the arbor A and adapted to be fixed in a selected position of adjustment along the arbor by a set screw 58. It will thus be clear that when the motor M is in operation the feed screw 54 will be driven and will feed through the nut to cause the carriage C and hence the tool holder H to be fed upwardly along the arbor duringl rotation of the holder on the arbor.

The pivotal mounting of the shaft 45 on the pin 47 permits the shaft to be rocked laterally to either of two eXtreme positions, in one of which the worm 48 meshes with the worm wheel 49 to drive the latter as shown in Fig. 3 and in the other of which it is unrmed in one of the brackets 51, and held lll the carriage andtool holder downwardly on the arbor to their initial ,positions after the completion of a cut upon the drum.

'The shaft 45 is normally urged outwardly from the worm wheel 49 to unmesh the worm 48 from the latter by means of a2 coil spring 60 interposed between and bearing against the arm 46 and an abutment 6l fixed to one of the brackets 40 as shown in Fig. l. The shaft 45 is maintained in either of the positions shown in Figs. 2 and 3 against the normal tendency of the spring 60 to move the shaft away from the worm wheel 49, by means of a pin 6la fixed to a lever 62 pivoted on a pin 63 and adapted to engage within either of two annular grooves 64 and 65 formed in the shaft '45, according as the lever 62 is rocked to the position shown in Fig. 2 or that shown in Fig. 8. The groove 64 being of greater depth than the groove 63 allows further outward movement of the shaft than does the groove 63, v

and the difference inthe depths of the two grooves is suicient to allow unmeshing of the worm 48 and worm wheel 49, with a discontinuance of the power feed of the carriage.

It will be noted that the lower extremity of l the feed screw 54 is provided with a reduced unthreaded portion 66 which is adapted to pass freely within the nut 57 so as to discontinue the upward feed of the carriage after a predetermined amount of travel of the carriage has been effected, so that possible dam` age to the machine is prevented. To further insure the machine against-damage as well as to notify the operator that a cut upon the drum D has been c mplet'ed, means is provided for operating an audible signal in the form of a bell 67 secured to the carriage C, as well as openinga switch 68 supplying current to the motor M and alsosccured to the carriage C.

This means in the present instance comprises a trip member T in the form of a rod having a vertical portion 69 vertically adjustable in the nut 57 and secured in a selected lposition of adjustment by a set screw 70; a

horizontal portion 71 extending outwardly from the lower end of the vertical portion 69 anddisposed in the path of an arm 72 for actuating the hammer 73 of the bell 67; and a second vertical portion 74 depending from the horizontal portion 71 and disposed in the path of the operating arm 75 of the switch 68.

The operation of the machine is as follows:

Assuming that the machine. is supported on the wheel W as shown in the drawings, and l with the worm 48 unmeshed from the worm wheel 49, the tool 18 is adjusted vertically on the arbor by manipulatinr the handle 59 unt-.1,

the tool is positioned at the lower edge of the drum D. The tool is then adjusted horizontally by manipulating'the handle'32 to effect the desired depth of et upon the tool.

The trip member T is adjusted vertically drum by the' will he sounded and the supply of current to the motor Ml discontinued. The lever 62 is then manipulated to mesh the worm 48 with the worm wheel 49 Vafter which the switch 68 is closed. lith the motor in operation, the tool holder H will be rotated and the carriage C fed upwardly on the arbor to accordingly draw the holder upwardly and thereby cause the tool to travel across the periphery of the drum, thus cutting a predetermined thickness of material from the drum and rendering the, latter perfectly concentric with and parallel to the axis of the wheel aXis.

Should the operator not be present when the cut is completed and should the ,bell fail to sound or be heard, or the trip member T fail to open the switch 68, and thuspermit the motor to continue to operate, the reduced unthreaded portion 66 of the feed screw 54, upon entering the nut 57 will automatically discontinue the upward feed ofthe carriage so that damage to the machine will be positively prevented.

From the foregoing description it will be manifest that broadly speaking I have provided a compact and portable machine capable of being supported by a brake drum carrying wheel when removed from the vehicle, and embodying an arbor, a carriage, and a tool carrying holder functionally related and (zo-operating in such manner as to insure that a cut taken upon the periphery of the drum will beabsolutely concentric with and parallel to the wheel aXis, all without the necessityof providing a heavy and expensive permanently installed machine, while affording all the desirable qualities of accuracy in'the results obtained, economy, and a miium expenditure of time and labor in perf mance of the truing operation Furthermore it will be noted from a con.- sideration-of Figures l and 2, that all the elements supported from the arbor A are so positioned with respect to each other as to lsettink up the machine on the work and the maintain the arbor in its upright position and hence the wheel W in its horizontal position, due to the fact that the weights of the various elements aie substantially counterbalancedabout the arbor and'therefore reduce to a minimum the possibility of tilting the arbor from its upright position.

`Although I have herein shown and "described only one form of brake-drum truing machine embodying my invention, it isto be understood that various changes and modifications may be madetherein without departing from the spirit of the invention and the vspirit and scope v.of ,the appended claims.-

I claim:

l. A brake drum truing machine comprising an arbor, means for fixedly securing the arbor to a brake drum carrying wheel in axriage so that with the tool of the holder engaging the periphery of the brake drum, a cut will be taken from the drum concentric with andparallel to the wheel axis, means for feeding the carriage along the shaft, and means for rotating the holder.

2. A brake drum truing'. machine comprising an arbor, means for lixedly securing the' arbor to a brake drum carrying wheel in axial alinement with the wheel axis, a carriage slidably mounted on the arbor and fixed against rotation thereon, a tool carrying holder rotatably mounted on the arbor and operatively connected to the carriage for sliding movement on the arbor by the carriage so that with the tool of the holder engaging the periphery of the brake drum, a cut wil.1 be taken from the drum concentric with and parallel to the Wheelaxis, means for feeding the carriage along the shaft, and means for rotating the holder, said feeding means for the carriage comprising a nut iixel to the arbor, a feed screw threadedly engaging the nut and connected to the carriage to move the latter along the'arbor in one direction or the other according as the feed screw is rotated in one directionor the other, and means for rotating the feed soclrew.

3. A brake drum truing machine comprising an arbor, means for fixedly securing the arbor to a brake drum carrying Wheel in axial alinement with the wheel axis, a carriage slidably mounted on the arbor and fixed against rotation thereon, a tool carrying holder rotatably mounted on the arbor and operatively connected to the carriage fol` sliding movement on the arbor by the carriage so that with the tool of the holder enz gaging the periphery of the brake drum, a

cut will be taken from the drum concentric with and parallel to the wheel axis, :means for feeding the carriage alongthe shaft, and means for rotating the holder, said feeding means for the carriage comprising a nut fixed to the arbor, a feed screw threadedly engagingI the nut and connected to the carriage to move the latter along the arbor in one direction or the other according as thel feed screw is rotated in one direction or the other, and means for rotating the feed screw, the feed screw having a reduced Unthreaded portion capable of passing freely through the ,nut to discontinue feeding of the carriage when the latter has been fed a predetermined distance along the arbor.

4. A brake drum truing machine comprising an arbor; means forfixedly securing the arbor to abrake drum carrying wheel in axial alinement with the wheel axis so that movement of the holder along the arbor by the carriage, yet rendering the holder free 5to rotate on the arbor so that with the tool of the holder engaging vthe periphery of the brake drumv a cut will be taken from the drum concentric with andjparallel to the axis of the wheel; means for feeding the carriage along the arbor; and means for rotating the holder.

5. A brake drum truing machine comprising an arbor; means for tixedly securing the arbor to a brake drum carrying wheel in axial alinement with the wheel axis ro that with the wheel disposed horizontally on a support, the arbor will extend vertically upwardfrom tfe brake drum side of the wheel and will be supported by the latter; a carriage slidably mounted on the arbor and fixed against rotation thereon; a tool carrying holder rotatably mounted on the arbor below the carriage; means for operatively Connecting the hoider to the carriage for sliding movement of the holder along the arbor by the carriage, yet rendering the holder free ,to rotate on the arbor so that with the tool of the holder engaging the periphery of the brake drum a cut will be taken from the drum concentric with and parallel to the axis of the wheel; means for feeding the carriage along the arbor; and means for rotating the holder, said means lfor operatively connecting the holder to the carriage comprising an axial socket in the carriage into which a portion of the holder extends andis rotatable, and means for retaining said portion of the holder against displacement from the socket.

6. A brake drum truing machine comprising van arbor; means for fixedly securing the arbor to a brake drum carrying Wheel in axial alinement with the wheel axis so that with the wheel disposed horizontally on a sup ort, the a'rborwill extend vertically upward fiom the brake drum side of the wheel and will be supported by the latter; a carriage slidably mounted on the arbor and fixed against rotation thereon; a tool carrying holder rotatably mounted on the` arbor below the carriage; means for operatively connecting the holder to the carrageffor sliding vmovement of the holder along the arbor by the carriage, yet rendering the holder free to rotate on the arbor so that with the tool of the holder engaging the periphery of the brake drum a cut will be taken from the drum concentric with and parallel to the axis of the wheel; means for feeding the carriage along the arbor; and means for rotatingthe holder,

said means for operatively connecting thel holder to the carriage comprising an axial socket in the carriage, a hub on the holder having an outwardly projecting annular flange disposed in the socket, thrust'bearings above and below the flange, and a plurality .of retaining elements extending into the socket i and engaging the lower thrust bearing to maintain the holder suspended from the carriage.

7. A brake drum truing machine comprising an arbor; means for fixedly securing'the. arbor to a brake drum carrying wheel in axial alinement with the wheel axis so that' y below the carriage; means lfor operatively connecting the holder to the carriage for sliding movement of the'holder along the arbor by the carriage, yet rendering the holder fi'reeto rotate on the arbor so'that with the tool of the holder engaging the periphery of the brake drum a cut will be taken from the drum concentric with and parallel to the axisv of the wheehmeans for feeding the carriage along the arbor: and means for rotating the holder,'the holder` being suspended from thecarriage so -as to be drawn upwardly on the arbor by the carriage in effecting cutting of the drum by the tool and i thereby prevent'chattering of the tool.

' 8. A brake drum truing machine comprising an arbor, means for fixedly 'securing the arbor toa brake drum carrying wheel in axial alinement with the wheel axis, a carriage slid-l ably mounted on the arbor and fixed against rotation thereon, a tool carrying holder rotatably mounted on the arbor and operatively connected to the carriage for sliding movemention the arbor bythe carriage so that with the tool of the holder engaging the periphery of the vbrake drum, a cut will be taken from the drum concentric with and parallel tothe wheel axis` means for feeding the carriage along the shaft, and means for discontinuing feeding of the carriage when the cut has'been completed. y l

v9. A brake drum truing machine comprising an arbor; means for fixedly securing the arbor to a brake drum carrying wheel in axial alinement` with the Wheel axis so that With the wheel disposed horizontally on a support, the arbor willextend vertically upward from the brake drum side of the wheel and will be supported by the latter; a carriage slidably mounted on the arbor and fixed against rotation thereon; a tool carrying holder rotatably mounted on the arbor below the carriage; means for operatively connecting the holder to the carriage for sliding movement of the holder along the arbor by the carriage, yet rendering the holder free to rotate on the arbor so thatwith the tool of the holder engaging the periphery of the' brake drum, a cut will be taken from the drum contenti-ic with and parallel to the axis of the wheel; a worm` wheel fixed to the holden-a drive shaft journaled in the carriage, a worm fixed to the shaft' and constantly meshing with the worm wheel to effect rotation of the latter and hence the holder, 'and means for driving the shaft.

l0. A brake drum truing machine comprising an arbor means for fixedly securing the arbor to a brake drum carrying wheel in axial alinement with the wheel axis so that with the wheel disposed horizontally on a support, the arbor will extend vertically upward from the brake drum side of the wheel and will be supported by the latter; a 'carriage slidably mounted on the arbor and fixed against rotati`on thereon; a tool carrying holder rotatably mounted on theV arbor below the carriage; means for operatively connecting the holder to the carriage for sliding movement of the holder along the arbor by the carriage, yetk rendering the holder free to rotate on the arbor so that with the tool of the holder engaging the periphery of the ybrake drum a ut will be taken from the drum concentric with and parallel to the axisof the wheel; a worm wheel fixed to the holder7 a drive shaft journaled in the. carriage, a worm fixed tothe shaft and constantly meshing with the Worm wheel to effect rotation of the latter and hence the holder, and means for driving the 'shaft comprising an electric motor supported on the carriage, and a driving connection between the motor and drive shaft.

11'. A brake drum truing machine compris.- ing an arbor; means for fixedly securing the arbor to a brake drum carrying Wheel in axial alinement with the Wheel axis so thatywith the vheel disposed horizontally on a support, the arbor will extend vertically upward from the brake drum side ofthe wheel and will be sup ported by the latter; a carriage slidably mounted on the arbor and fixed againstrotati-on thereon; a. tool carrying holder rotatably bor so that with ,the tool of the holder engaginar the periphery of the brake drum a cut will be taken from the drum concentric with and parallel to the axis of the wheel; a worm wheel fixed to the holder, a drivev shaft journaled in the carriage,-a worm fixed lto the shaft and constantly meshing with the worm wheel to effect rotation'of the latter and' hence the holder, a second shaftjournaled in the carriage, a worm wheel fixed to the second shaft and meshing with said worm, a nut fixed .to the arbor, a feed screw threadedly engaging thenut and connected to the carriage to move the latter along the arbor in response to rotation of the feed screw, means for operatively connecting the second shaft and feed screw for rotation of the latter from the seeond shaft, and an electric motor supported by the carriage for driving the first mentioned shaft. I

12. A brake drum truing machine comprising an arbor; meansfor fixedly securing the arbor to a brake drum carrying wheel in axial alinement with the. `wheel axis so that with the wheel disposed horizontally on a support, the arbor will extend vertically upward from the brake drum side of the wheel and will be supported by the latter; a carriage slidably mounted on the arbor and fixed against rotation thereon: a tool carrying holder rotatably mounted on the arbor below the earriage; means for operativelv conne'fting't-he holder to the carriage for sliding movement of the holder alongthe arbor bv the carriage, yet rendering the holder free to rotate onthe arbor so that with the tool of the holder engaging the periphery yof the brake drum a cut will be talfen from the drum concentric with and parallel to the axis of the wheel: a worm wheel fixed to the holder. a drive shaft journaled in the carriage, a worm fixed to the shaft and constantly meshing with the worm wheel to effect rotation of the latter and hence the holder, a second shaft journaled in the carriage, a worm wheel fixed to the second shaft and meshing with said worm. a worm fixed to the second shaft, a third shaft -iournaled in the carriage. a worm Wheel fixed to the third shaft and meshing with the second mentioned worm. a nut fixed to the arbor, a feed screw threadedly engaging the, nut and connected to the carriage. to move the latter along the arbor in response to rotation of the feed screw, a pair of meshing bevel gears fixed vto the feed screw and third shaft, and an electric motor supported 13. Ina brake drum truing machine having a carriage and means for feeding` the carriage, a disconnectible power feed device comprising a shaft, gears for operatively connecting the shaft with the feeding means to drive the latter in response to rotation of the shaft, means for mounting the shaft for rotation and for rocking movement laterally to occupy one position wherein the gears will mesh and another position wherein the gears will be unmeshed, means for normally urging the shaft to the position wherein the gears will be meshed, and means for retaining the shaft in either of its positions against the action of said urging means.

14. Ina bra-ke drum truing machine having a carriage and means for feeding the carriage, a disconnectible power feed device comprising a shaft, gears for operatively connecting the shaft with the feeding means to drive the latter in response to rotation of the shaft, means for mounting'the shaft for rotation and for rocking movement laterally to occupy one position wherein the gears will mesh and another position wherein the gears will be unmeshed. means for normally urging the shaft to the position wherein the gears will be meshedwand means for retaining the shaft in either of its positions against the action of said urging means. comprising a pair of annular grooves of different depths formed in the shaft, and a. pivoted lever having a pin engaging within one or the other of said grooves according as the lever is moved to one position or another.

15. A brake drum truinfrmafhine comprising an arbor. means for fixedly securing the arbor to a bralre drum carrying wheel in axial alinement with the wheel axis so that with the wheel resting horizontally on a support, the arbor will extend verticallv upward from the brake drum side of the wheel and will be supported in its upright position hv the wheel-a tool carrying holder rotatablv and slidablv mounted on the a-rborfand meansy supported from the arbor for driving the holdcr to effect rotation and sliding movements thereof on the arbor so that with the tool of the holder engaging the periphery of the brake drum a cut will he taken from the peripherv. the elements supported from the arbor being so positioned with respect to each other as to maintain the arbor in its upright position and hence the wheel in its horizontal position.I

16. A brake drum truing machine comprisino: an arbor. means for fixedly` securing the arbor toa brake drum carrying wheel in raxial alinement with the wheel axis so that with the wheel resting horizontally on a support. the arbor will extend vertically upward from the brake drum sideA of the wheel and will be supported in its upright position bv the wheel. a tool carrying holder rotatably and slidablv mounted on the arbor. and means supported from the arbor for driving the holder to effect rotation and sliding movements thereof on the arbor so that with the tool of the holder engaging the periphery of the brake drum a cut will be taken from the periphery. the elements supported from the. arbor being so positioned with respect to each other that their weights will substantially counterbalance each other about the arbor to reduce to a minimum the possibili tvv of tilting thev arbor from its upright position and hence'tilting the"wheel from its horizontalposition. l y

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