US2716312A - Truing device for face-type diamond abrasive wheels - Google Patents

Description

Aug. 30, 1955 TRUING DEVICE FOR FACE-TYPE DIAMOND ABRASIVE WHEELS E. W. SPEICHER Filed March 9, 1955 IN V EN TOR. 5L MEI? M/ 5P5! c1452 ATTORNEY United States Patent TRUING DEVICE FOR FACE-TYPE DIAMOND ABRASIVE WHEELS Elmer W. Speicher, Birmingham, Mich.

Application March 9, 1953, Serial No. 341,060

14 Claims. (Cl. 51-168) This invention relates to a face-type cup-shaped diamond abrasive wheel truing device and more particularly to a device in which a somewhat yielding and compressible backing member is interposed between the abrasive wheel and a relatively non-yielding and non-compressible wheel mounting plate rotatable upon a driving spindle, whereby the abrasive face surface is arranged to lie in a single plane at right angles to the axis of rotation.

Most cup-shaped face-type diamond abrasive wheels are arranged with a center bore, a counterbore and an outer annular peripherally adjacent face, on one or both sides of the wheel, containing the abrasive diamond particles. Diamond abrasive wheels are used in industry where tungsten-carbide tipped tools are required. Such wheels are very expensive in comparison with other abrasive wheels.

However, the process of manufacturing these diamond faced wheels does not always produce perfectly trued wheels. Or if true, the means upon which they are mounted may not lie in a plane normal to the axis of the rotating driving spindle. In order to make the most economical use of such expensive abrasive wheels, it has been found that truing the face of the wheel to run in a single plane at right angles to the axis of rotation results in longer wheel life, better tool grinding and sharpening, and longer spindle life. The diamond covered face of the wheel is not gouged out in spots, as happens when the face is not trued up to rotate in a single plane. The high spots which then result occasion spot wear of the diamond face, accompanied by chatter marks on the tool. Vibration effects are also noted in the abrasive wheel face, the tool edges and the driving spindle.

Diamond abrasive wheels, other than true periphery wheels, may also be trued by the inventive device here described and claimed. Such wheels would include diamond abrasive surfaces at an angle to the axis of rotation, radius dressing wheels, or combinations of angles and radii.

To avoid the defects and failures above referred to, the novel and inventive face-type diamond abrasive wheel truing device here described may be employed. Reference is made to my earlier United States Patents Nos. 2,546,529 issued Mar. 27, 1951 and 2,577,042 issued December 4, 1951, in which other wheel truing devices are disclosed and claimed.

It is an object of this invention to combine a cup shaped face-type diamond abrasive wheel with a backing member being somewhat yielding and compressible in character upon a relatively non-yielding wheel mounting plate which is rotatable upon a driving spindle.

it is another object to provide a device for truing a diamond faced abrasive wheel without modifying the Wheel or the mounting plate as they are normally produced and used at the present time.

Another object of the invention is the provision of such a diamond abrasive wheel, backing member and mounting plate with openings therethrough to receive and hold wheel mounting screws, or other fastening 2,716,312 Patented Aug. 30, 1955 means, which will combine these elements into a unit, and at the same time permit the truing of the face of the wheel to cause it to run or rotate in a single plane.

Still another object is the provision of a truing device in which vibration effects of the diamond abrasive wheel will be held to a minimum, and absorption of grinding shocks due to the cushioning effect of a somewhat yielding and compressible backing member behind the wheel will materially lengthen the life of the trued wheel.

A further object is to provide an extremely simple means of truing a facetyp'e, cup-shaped diamond abrasive wheel arranged to be mounted on standard abrasive wheel mounting plates aflixed to rotatable driving spindles, by interposing a somewhat yielding and compressir ble backing member between the back of the wheel and the mounting plate, so that upon tightening of the wheel to the mounting plate, the face of the wheel is brought into a single plane, normal to its axis of rotation, simply through selective adjustment and tightening of the Wheel mounting screws.

Still another object of the invention is to provide for a combination of certain elements of the device into a more desirable manufacturing and sales structure, as for instance unitizing the abrasive wheel and the resilient backing member, or where a steel support plate is used for a composition bakelite wheel unitizing the abrasive wheel to the steel support plate and to the resilient backing member.

Additional objects will become apparent from the description of the invention given below.

The description together with the appended drawing is a disclosure of some forms which the invention may take, and is not intended to be a limitation of the forms or variations which persons skilled in the art may make. The terms are used for purposes of description and not of limitation.

Referring now to .the drawing annexed hereto and forming an integral part of this specification,

Fig. 1 is a vertical sectional view of the inventive device on the line 11 of Fig. 2.

Fig. 2 is a side elevation of the inventive device.

Fig. 3 is a vertical fragmentary sectional view similar to Fig. 1, showing the diamond abrasive face at an angle other than a right angle, to the axis of rotation.

Fig. 4 is a vertical fragmentary sectional view, similar to Fig. 1, showing a modification of the inventive structure.

As shown in Fig. 1, a cup-shaped face-type diamond abrasive wheel 10 is arranged over a rubber or plastic type disc shaped backing member 12, the wheel 10 being mounted on the rotatable spindle mounting flange plate 1.4 by means of screws 16. A rotatable driving spindle 17, having a forwardly projecting pilot 13, supports the inventive device as shown.

The diamond abrasive grinding wheel 10 is of standard cup-shaped construction, consisting of a counterbored body 19 containing a center spindle pilot opening 20. In the body 19 are several countersunk holes 21, arranged in a suitable bolt circle. Most diamond abrasive wheels 10 range from 6" to 10" in diameter, the 6" wheels having 4 mounting screws 16, and the 10" wheels having 6 screws. The diamond coated face 22 of the wheel 10 is generally arranged to face outwardly of the machine spindle 1'7, and is caused to rotate substantially in a single plane at right angles to the axis of rotation of the spindle. The rear side 23 of the wheel 10 is generally fiat and square with the axis of rotation of the wheel.

The backing member disc 12, which is shown in the drawing as composed of a rubber or plastic material, may also be formed from such materials as felt, leather, or textile fabrics. Or it may be fashioned from any other materialwhich is somewhat yielding, resilient and comthe wheel of Fig. 1.

pressible in nature, and yet which does not shatter or physically decompose under the adjustment pressures required. The member 12 should have sufficient body to absorb and yet resist the adjustment pressures to be described and grinding shocks of tool grinding and sharpening. Hard, substantially non'yielding materials would not appear to be suitable for this application as a backing member, because the selective adjustment pressure applied by screw tension in turning mounting screws 16 might warp or distort the wheel 10 more than the intermediate backing member 12. The backing member 12 is arranged with non-threaded holes 24, through which screws 16 are passed to the spindle mounting flange plate 14. A central pilot opening 26 in member 12 permits the spindle pilot 18 to pass therethrough. The mounting screws holes 24 of backing member 12 are arranged on the same bolt circle as for the diamond abrasive wheel 10. The fiat sides 27 of the resilient compressible backing member 12 are substantially parallel to each other.

The mounting flange plate 14 is arranged with threaded holes 28 to take and receive the threaded shanks of mounting screws 16. The bolt circle and spacing of the holes 28 in flange plate 14 is the same as for holes 21 in diamond wheel counterborecl body 19. Mounting flange plate 14 is generally made of steel and welded, integrally formed, or otherwise fixedly mounted on rotatable driving spindle 17, and transmits rotation to the diamond faced abrasive wheel 10. Spindle pilot 18 is provided for centering the backing member 12 and wheel 10, though it may be dispensed with if desired.

A dial type indicating device 30 is used to indicate the out of plane portions of the wheel face 22 while it is being trued up, and to indicate when the truing operation has been completed.

In Fig. 3, the diamond flat abrasive face 32 is at an angle other than 90 to the axis of rotation. Such a Wheel may also be trued, and by the same means as for However, the indicator 30 should be positioned with its stem normal to the plane of the face 32, a frusto-conic form, in order to properly determine trueness of the abrasive surface in its rotation.

Except for diamond abrasive surface 32, the remaining elements of the wheel 10 of Fig. 3 bear the same reference numerals as those given in Fig. 1.

As shown in Fig. 4, diamond abrasive wheel 10a has a body 34 of a hard composition material such as bakelite, with the diamond abrasive face 22 thereon as in Wheel 10. As additional support for such a wheel 111a, and in order to prevent cracking of the Wheel when the mount ing screws 16 are drawn up with selective adjustment pressure, a backing plate or disc 36 of steel or other suitable material is placed directly behind wheel 111a. Plate 36 has holes 38 therein on the bolt circle of wheel 10a to receive and pass the screws 16 therethrough. Central pilot opening 39 permits the spindle pilot 18 to pass through plate 36. The sides 4-0 of the plate 36 are flat and parallel.

It should be noted here that another preferred construction of the inventive device is the combination of wheel 10 and backing member 12 into a unit structure. This is accomplished by cementing one side 27 of the rubber type resilient backing member 12 to the back side 23 of wheel 10. The cementing process may be any one of those well known in the art. Sometimes a layer of cement (not shown) is applied to the wheel side 23 for bonding backing member 12 to it. Or there may be other processes more desirable or suitable for achieving this result. A backing member 12 bonded or cemented to wheel 10 does, moreover, represent a simple and efficient way of embodying the inventive device into a satisfactory marketable construction.

In the case where steel plate 36 is employed to strengthen wheel 10a against cracking under undue selective adjustment pressures of mounting screws 16, it is also preferred to combine the three elements into a 4 unit, or to combine two of them into a unit. The rear side 23 of wheel 10a can be cemented or bonded to one side 40 of steel plate 36, and side 27 of backing member 12 can be cemented or bonded to the other side 40 of steel plate 36, forming a complete unitized combination embodying the inventive construction.

Or, the side 40 of steel plate 36 which is continguous to backing member 12 can be cemented or bonded to a side 27 of member 12, the wheel 10a remaining as a separate element of the combination.

In operation, the inventive device consisting essentially of diamond faced abrasive wheel 10, backing member 12, spindle mounting flange plate 14 and driving spindle 17 is combined into unit device by wheel mounting screws 16, which not only hold the wheel 10 to the plate 14, but also true the face 22 of the wheel by selective adjustment and tightening. As screw pressure is applied in each quadrant or segment of the wheel 10, that portion of the wheel face 22 therein contained is aligned with the other segments, as indicated by the dial indicator 30. As the screw pressure is applied, the backing member 12, which is yielding, resilient and compressible, though not destructible under the quantum of screw pressure normally applied, will yield and com v press to permit the wheel quadrant or segment to move toward the spindle mounting flange plate 14.

Because a diamond abrassive wheel face 22 out of plane, with high and low spots, would set up certain deleterious vibrations and effects in the work and in the wheel face, as well as in the driving spindle, it is very important that any diamond face distortions be corrected. This is done by selectively adjusting the mounting screws 16 which hold the wheel 10 to the mounting flange plate 14. As the adjusted mounting screws 16 apply pressure to the wheel 10 and against the backing member 12, the dial indicator 3t) will show when the diamond face 22 has been brought into a single plane. This plane will be at right angles to the axis of rotation of the driving spindle 17, for the wheel 1% of Fig. 1.

The several distinct advantages in truing the wheel face 22 by simply adjusting the tightness of the mounting screws 16 as required, are readily apparent. The inclusion of a backing member 12 of the type described eliminates the need for special mountings, or additional adjusting screws with their complementary threaded or non-threaded holes, or other means, while providing a suitable means for properly truing the wheel face 22.

The method of accomplishing this important operation is simple, and requires no modification of either the wheel 10 or the spindle mounting plate 14. Simply by interposing a backing member 12 of suitable rubber, plastic, felt, leather or textile material, the important wheel truing operation is caused to be accomplished with ease and facility, and without any substantial expense.

The steel backing plate 36 for Wheel 10a, shown in Fig. 4, is provided to diminish possible cracking of the Bakelite body 34 in such a wheel. Some wheel mounting operators are more careful than others, and in many cases wheels 1011 are cracked due to careless mounting. Although the rubber type resilient backing member 12 will assist materially in reducing the incidence of such cracking, it is considered desirable to insert a steel backing member 36, having a high-non-distortable characteristic, when Bakelite body wheels 10a are used.

So far as the operation and functioning of the in ventive device is concerned, it makes little difference whether the elements of wheel 10, backing member 12 and mounting flange plate 14 are single members, or whether backing member 12 is bonded or cemented to wheel 10 as described above. Functionally, they will operate and achieve the desired purpose in the same manner. The same is true in those cases where wheel 1901 steel plate 36, and backing member 12 are unitized.

The ease and facility of manufacturlng thesecornb1nations provides a customer forabrasive wheel .10 or "a the opportunity to purchase a complete unit, and does not require'him to goout and buy steel plate 36 or back ing member 12 separately. Theinconvenience and additional cost involved in so doingis eliminated by manufacturing the elements in combinations as above described.

Grinding shocks caused by .a tungsten-carbide tipped tool being thrust roughly into the abrasive face 22 of a diamond wheel 10, are the bane of the wheel owners existence. If the tool isnotproperly prepared by rough grinding and is not handled carefully in its application to wheel 10, the wheel can be -gouged out, will break down and be destroyed in a very short space of time, with considerable loss. The-rubber type shock absorbing backing member 12here described,-in additionto yielding under pressure from the mounting screws 16, also :provides an excellent shock absorber for the tool grinding operation itself, thus materially increasing wheel life and efficiency.

A modification of the mounting screw 16, as shown, is the use of screws and nuts, wherein all of the holes through the wheel 10, backing member .12 and mounting flange plate 14 become true bores, nonthreaded, and the units are combined by means of flat headscrews and nuts arranged over lock washers. Such means, of course, are well known in the art.

It is recommended as a preferredspecification, where rubber is employed as a backing member material, that it be oil resistant, as is neoprene rubber. Where plastic materials are used, vinyl chloride compositions are .preferred. These preferences are variable, depending upon the peculiar circumstances of each application.

For 6" diameter wheels, a A" thick neoprene rubber backing member 12 will serve satisfactorily. The same thickness is suitable for a 10 wheel as well. The body afforded by a good rubber or plastic material in the backing member 12 provides an important factor in properly backing the wheel.

In diamond face-typeabrasive wheel construction, it is important to make the abrasive face 22 and the rear side 23 of wheel 10 square with the pilot bore 20. However, for the wheel 10 of Fig. 3, the relationship of the frusto-conic face 32 to the axis of revolution and the pliot bore '20 is of very great importance. It can easily embodied in the wheel when the user gets it, theproblem of wheel truing proceeds as above described, and a line on the abrasive surface related to the axis of revolution or of rotation can be indicated withdial indicator to show when wheel 10 is running true and square with the axis of rotation.

In some cases, hard materials other than diamonds may be employed as abrasive on these wheels, and it is to be understood that the inventive device-here described and claimed is extendable also to such abrasive coated wheels.

It is also tobe understood that the details of the foregoing specification may be changed and varied ingreater or lesser degree without departing from the essence of my invention.

I claim:

1. The combination of a face-type cup-shaped diamond abrasive wheel having an annularflat abrasive surface normal to the axis of rotation, a rotatable driving spindle having a wheel mounting flange .plate fixedly attached thereon at its outer end, said mounting flange plate being arranged at right angles to its axis-of rotation, a com- ,pressible flatdisc-type wheel supporting backing member intermediate said wheel and said mounting flange plate, said wheel, backing member and flange plate being in close contiguous lateral contact with each other in that order, and mounting screws securing said wheel over said backing member to said mounting flange plate in adjusted position so that said flat abrasive wheel surface lies in a plane at right angles to the axis of rotation of said driving spindle, said backing member adapted to support said wheel surface in said plane.

2. In combination, a cup-shaped diamond abrasive wheel having anannular flat abrasive surface normal to the axis of rotation, a rotatable driving spindle having a mounting flange plate fixedly arranged thereon at its outer end, and at right angles to its axis of rotation, a wheel supporting compressible flat disc-type backing member intermediate said wheel and said mountingtflange plate, said wheel, backing member and flange plate being in close contiguous lateral contact with each other in that order, andmounting screws securing said wheel oversaid backing member to said mounting plate: in such a way that saidwheel flat abrasive surface is disposed in alplane at right angles to the axis of rotation of said driving spindle, said backing member adapted to support said Wheel surface in said disposed plane.

3. In combination, a rotatable spindle having a mountting flange plate fixedly attached on its outer end and at right angles totheaxis of rotation of said spindle, a diamond abrasive Wheel having an annular fiat abrasive surface of diamond particles adjacent the periphery of said wheel, on one side thereof and at right angles to the axis of rotation, a wheel supporting compressible fiat disc-type backing member of a resilient material intermediate the backofsaid wheel and said mounting flange plate,.said wheel, backing member and flange plate being in close contiguous lateral contact with each otherlin that order, andmounting screws circularly spaced apart within openings in said wheel, said backing member and said mounting flange plate securing said wheel over said backing member to said mounting flange plate so that said wheel flat abrasive surface lies in a plane at right angles to .the axis of rotation, said backing member adapted to support said wheel surface in said plane.

4. The combination of a cup-shaped face-type diamond abrasive wheelhaving an annular flat abrasive surface at right angles to its axis of rotation, a rotatable driving spindle having .a wheel mounting flange plate normal tothe axis of rotation and fixedly attached to said spindle at the outer end thereof, said mounting flange ,plate having threaded screwengaging openings circularly spaced .apart therein axially parallel to the axis of said spindle, a wheel supporting fiat disc-type backing member of a resilient material intermediate the back of said wheel and said mounting flange plate and threadedly engaged in said screw engaging openings of said mounting flange plate so that said wheel flat abrasive surface lies in a plane at right angles to the axis of rotation of said spindle, said wheel, backing member and flange plate being in close contiguous lateral contact with each other in that order, said backing member adapted to support said wheel surface in said plane.

5. In combination, a rotatable spindle havinga mountingplate at one end thereof arranged atright angles to the axis of rotation, a diamond cup-shaped face-type abrasive wheel having an annular flat surface at right angles to the axis of rotation, a wheel supporting compressible resilient flat disc-type backing member intermediate said wheel and said mounting plate, said wheel, backing member and mounting plate being in close, contiguous lateral contact with each other in that order, and pressure applyingmounting screws securing said wheel to said mounting plate over said backing member so that said flat abrasive surface is disposed in a single plane at right angles to its axis of rotation, said backing member adapted to support said wheel surface insaid single plane.

6. In combination, a diamond cup-shaped face-type abrasive wheel having an annular flat surface adjacent its peripheral edge and at right angles to its axis of rotation, a rotatable driving spindle having a mounting flange plate at one end thereof arranged normal to the axis of rotation, a wheel supporting resilient flat disc-type backing member intermediate said wheel and said mounting plate, said wheel, backing member and flange plate being in close contiguous lateral contact with each other in that order, said wheel having a counterbored face centrally disposed therein with circularly arranged spaced apart screw receiving openings therein, and pressure applying mounting screws in said screw receiving openings securing said wheel to said mounting plate over said backing member so that said flat abrasive surface is disposed in a single plane at right angles to its axis of rotation, said backing member adapted to support said wheel surface in said single plane.

7. In combination, a diamond cup-shaped face-type abrasive wheel having an annular flat surface at right angles to its axis of rotation, a rotatable spindle having a mounting flange plate at one end thereof arranged normal to the axis of rotation, a pilot portion axially projecting from said spindle, a wheel supporting resilient rubber flat disc-type backing member intermediate said wheel and said mounting flange plate having an opening therethrough for said spindle pilot portion, said wheel, backing member and flange plate being in close contiguous lateral contact with each other in that order, and adjustment pressure applying mounting screws securing said wheel to said mounting plate over said backing member, said screws being circularly spaced about said wheel parallel to the axis of rotation and operatively bearing upon said wheel against said backing member in selective pressure adjustment of said wheel so that said wheel flat abrasive surface lies in a plane at right angles to its axis of rotation, said backing member adapted to support said wheel surface in said plane.

8. In combination, a rotatable face-type abrasive wheel having an annular flat abrasive surface at right angles to its axis of rotation, a rotatable driving spindle having a wheel mounting flange at one end thereof arranged normal to its axis of rotation, a wheel supporting compressible, resilient flat disc-type backing member intermediate said Wheel and said mounting flange, said Wheel, backing member and mounting flange being in close contiguous lateral contact with each other and in that order, and pressure applying wheel mounting means securing said wheel to said mounting flange over said resilient backing member,

said pressure applying means operatively bearing upon said wheel against said backing member in selective pressure adjustment so that said flat abrasive surface lies in a plane normal to its axis of rotation, said backing member adapted to support said wheel surface in said plane.

9. In combination, a rotatable face-type cup-shaped abrasive wheel having an annular flat abrasive surface on the front side of said Wheel at right angles to its axis of rotation, a rotatable driving spindle having a Wheel mounting flange at one end thereof arranged normal to its axis of rotation, a wheel supporting compressible resilient flat disc-type backing member cemented to the back side of said wheel and disposed between said wheel and said mounting flange, said wheel, backing member and mounting flange being in close contiguous lateral contact with each other in that order, and pressure applying wheel mounting means securing said wheel to said mounting flange, said pressure applying means operatively bearing upon said Wheel against said backing member in selective pressure adjustment so that said flat abrasive surface lies in a plane normal to its axis of rotation,

said backing member being adapted to support said wheel surface in said normal plane.

10. In combination, a rotatable face-type cup-shaped abrasive wheel having an annular flat abrasive surface at right angles to its axis of rotation, a rotatable driving spindle having a wheel mounting flange at one end thereof arranged normal to its axis of rotation, a relatively nonyielding and non-compressible metal wheel support, a compressible resilient flat disc-type backing member intermediate said wheel support member and said mounting flange, said wheel, wheel support, backing member and mounting flange being in close contiguous lateral contact with each other in that order, and pressure applying wheel mounting means securing said wheel to said mounting flange over said support member and said backing member in that order, said pressure applying means operatively bearing upon said wheel against said support member and said backing member in selective pressure adjustment so that said flat abrasive surface lies in a plane normal to its axis of rotation, said backing member being adapted to support said wheel surface in said normal plane.

ll. In combination, a face-type cup-shaped abrasive wheel having an annular flat abrasive surface on the front side of said wheel at right angles to its axis of rotation, a rotatable driving spindle having a wheel mounting flange at one end thereof arranged normal to its axis of rotation, a relatively rigid, hard metal wheel support member bonded to the back side of said wheel, a compressible resilient flat disc-type backing member intermediate said wheel support member and said mounting flange, said wheel, support member, backing member and mounting flange being in close contiguous lateral contact with each other in that order, and pressure applying wheel mounting means securing said wheel to said mounting flange over said support member and said backing member in that order, said pressure applying means operatively bearing upon said wheel against said support member and said backing member in selective pressure adjustment so that said flat abrasive surface lies in a plane normal to its axis of rotation, said backing member being adapted to support said wheel surface in said normal plane.

12. In combination, a face-type cup-shaped diamond abrasive wheel having an annular flat abrasive surface on the front side of said wheel at right angles to its axis of rotation, a rotatable driving spindle having a wheel mounting flange at one end thereof arranged normal to its axis of rotation, a wheel supporting compressible flat disc-type backing member bondedto the rear side of said wheel and disposed between said wheel and said mounting flange, said wheel, backing member and mounting flange being in close contiguous lateral contact with each other in that order, and pressure applying Wheel mounting means securing said wheel to said mounting flange, said pressure applying means operatively bearing upon said wheel against said backing member in selective pressure adjustment so that said flat abrasive surface lies in a plane normal to its axis of rotation, said backing member being adapted to support said wheel surface in said normal plane.

13. In combination, a face-type cup-shaped diamond abrasive wheel having an annular flat abrasive surface on the front side of said wheel at right angles to its axis of rotation, a rotatable driving spindle having a wheel mounting flange at one end thereof arranged normal to its axis of rotation, a relatively rigid, hard metal Wheel sup port member contiguous to the rear side of said wheel, a compressible resilient flat disc-type backing member intermediate said wheel support member and said mounting flange, said wheel, support member, backing member and mounting flange being in close contiguous lateral contact with each other in that order, and pressure applying wheel mounting means securing said wheel to said mounting flange over said support member and said backing member in that order, said pressure applying means operatively bearing upon said wheel against said support member and said backing member in selective pressure adjustment so that said flat abrasive surface lies in a plane normal to its axis of rotation, said backing member being adapted to support said wheel surface in said normal plane.

14. In combination, a face-type cup-shaped diamondabrasive Wheel having an annular flat abrasive surface on the front side of said wheel at right angles to its axis of rotation, a rotatable driving spindle having a wheel mounting flange at one end thereof arranged normal to its axis of rotation, a relatively rigid hard metal wheel support member bonded to the rear side of said wheel, a compressible resilient fiat disc-type backing member intermediate said Wheel support member and said mounting flange, said wheel, support member, backing member and mounting flange being in close contiguous lateral contact with each other in that order, and pressure applying wheel mounting means securing said wheel to said mounting flange over said support member and said backing member in that order, said pressure applying means operatively bearing upon said wheel against said support member and said backing member in selective pressure adjustment so that said flat abrasive surface lies in a plane normal to its axis of rotation, said backing member being adapted to support said wheel surface in said normal plane.

References Cited in the file of this patent UNITED STATES PATENTS

Images