US3120084A

US3120084A - Abrasive finishing tool

Info

Publication number: US3120084A
Application number: US232417A
Authority: US
Inventors: James M Phillips
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-10-23
Filing date: 1962-10-23
Publication date: 1964-02-04
Anticipated expiration: 1981-02-04

Description

Feb. 4, 1964 J. M. PHILLIPS 3,120,034

ABRASIVE FINISHING TOOL Filed 001;. 25, 1962 2 Sheets-Sheet 1 15 m ll'JFllllllllI y z7 INVENTOR.

BY W zwxmfm AT TOKNE Y5 Feb. 4, 1964 J. M. PHILLIPS 3,120,084

ABRASIVE FINISHING TOOL Filed Oct. 23, 1962 2 Sheets-Sheet 2 ATTORNE Y5.

United States Patent 3,120,084 ABRASWE FINISHING TOGL James M. Phillips, R0. Box 102, Stanford, Ky. Filed Oct. 23, 1962, Ser. No. 232,417 6 Claims. (1. 51-205) This invention relates to a hand tool for use in finishing the surface of a workpiece and is particularly directed to a tool of this nature utilizing a plurality of demountable abrasive blocks or the like which are adapted to accommodate workpieces having various surface profiles.

One of the primary objectives of the invention has been to provide a holder, combined with a plurality of abrasive blocks, the holder being provided with a handle and with a releasable clamping mechanism, adapting the several abrasive blocks to be interchangeably mounted in the holder in a rapid, convenient manner.

Described briefly, the abrasive block holder is generally U-shaped as viewed from the side, comprising a horizontal handle, a fixed clamping bracket depending downwardly from one end portion of the handle, and a pivotally mounted shiftable clamping bracket depending downwardly from the opposite end portion of the holder. The handle includes a spring-loaded detent mechanism engageable with the shiftable bracket and adapted to releasably latch the shiftable bracket in a clamping position, with a selected abrasive block clamped endwisely between the two brackets.

In accordance with the present invention, the interchangeable abrasive blocks are formed of wood, plastic or other appropriate material, each block having several abrasive surface profiles which may be presented selectively to the work surface. By way of example, the several abrasive surfaces of the abrasive block may be flat, convex or concave, or a combination of such contours extending longitudinally thereof to suit the surface profile of the workpiece which is to be finished. The blocks may also be provided with abrasive particles of various commercial grades in the range of fine to coarse, depending upon the requirements of different finishing operations.

A further objective of the present invention has been to provide the combination of a block holder and a plurality of abrasive blocks, each which may be rotated or indexed about its longitudinal axis and clamped in a selected position in the holder to present a selected abrasive surface to the work surface.

According to this aspect of the invention, the opposite end portion of each abrasive block is slotted to form an indexing keyway, the keyway being related to the several surfaces of the block for indexing purposes. The fixed and shiftable mounting brackets of the holder are each provided with a transverse key adapted to interfit the indexing keyways at opposite ends of the block. By way of example, an abrasive block having four longitudinal abrasive surfaces may be provided at opposite ends with two bisecting keyways or slots dimensioned to be en aged by the transverse keys of the brackets. In order to index the block with reference to the holder, the shiftable bracket is unclarnped, then the block is rotated about its axis to bring the selected abrasive surface to its working position. Thereafter, the shiftable bracket is again latched in its clamping position, such that the block is rigidly keyed or clamped against rotary and longitudinal motion relative to the holder.

A further objective of the invention has been to provide a self-locking arrangement, whereby the shiftable bracket of the holder is pivoted in an automatic manner under pressure to its clamping position to facilitate the indexing or interchanging of the abrasive blocks.

Described briefly, the shiftable bracket is provided with an aperture below its pivotally mounted end, combined with a leaf spring having one end connected to the 3,120,084 Patented Feb. 4, 1964 handle and having its outer end passing through the aperture of the bracket. The projecting end of the leaf spring is bent to the form of a generally triangular detent which is normally spring urged by the leaf spring in an upward direction toward the handle. The detent provides a wedging surface which engages the upper edge of the aperture and creates a wedging action which forces the bracket under pressure toward the fixed bracket.

In order to release the abrasive block, the springloaded detent is forced downwardly with the thumb or finger, adapting the bracket to pivot outwardly to its release position, with its transverse key disengaged from the indexing keyway of the block for replacement or indexing. After the abrasive block is indexed or replaced, the shiftable bracket is swung toward the end of the block to engage its transverse key with the keyway. This causes the spring-loaded detent to snap upwardly, whereby its wedging surface forces the bracket automatically to its clamping position thus clamping the abrasive block in place in a rapid convenient manner.

The various features and advantages of the invention will be more clearly apparent to those skilled in the art from the following detailed description, taken in conjunction with the drawings.

In the drawings:

FIGURE 1 is a perspective view of a hand tool constructed according to the invention, showing one of the abrasive blocks clamped in the holder and ready for use.

FIGURE 2 is a side elevation taken from FIGURE 1, with parts of the abrasive block broken away to illustrate more clearly the arrangement of slots in the block which are engaged by the opposed clamping brackets of the holder. This view shows in broken lines, the position of the shiftable bracket in its released position for removal or replacement of the abrasive block.

FIGURE 3 is an enlarged cross sectional view taken along line 3-3 of FIGURE 2 detailing the shiftable bracket and latching device with reference to the handle.

FIGURE 4 is a fragmentary top plan view of the shiftable clamping bracket and its latching detent in the clamping position corresponding to FIGURE 2.

FIGURE 5 is an enlarged fragmentary view of the shiftable bracket with the detent in the unclamping position, and with the bracket swung to its block release position.

FIGURE 6 is a fragmentary view, generally similar to FIGURE 5, showing the motion of the shifta'ble bracket toward the clamping position and the wedging motion of the detent toward its latching position.

FIGURE 7 is a fragmentary view similar to FIGURE 6, showing the parts in the clamping position corresponding to FIGURES l and 2. I

FIGURES 8 to 13 inclusive illustrate a series of abrasive blocks adapted to be mounted in the hand tool showing a number of typical cross sectional contours for finishing corresponding workpiece surfaces.

General Arrangement Described generally with reference to FIGURES 1 and 2, the abrasive hand tool comprises a holder, indicated generally at \1, adapted to clampingly engage the interchangeable abrasive blocks, one of which is indicated generally at 2 in these views. As viewed from the side (FIGURE '2) the holder is generally U-shaped and comprises a handle 3 (FIGURES 1 and 2) having a fixed clamping bracket 4 at one end and a shirftable clamping bracket 5 at its opposite end. The shiftable bracket 5 is latched in clamping position by a spring-loaded releasable detent, which is indicated generally at 6.

The spring loaded detent 6 permits the abrasive block to be unclamped for replacement by gripping the handle with one hand so as to facilitate the operation of inter- 3 changing the blocks 2 with the other hand. Thus, as indicated in the broken line in FIGURE 1, the handle 3 is gripped with the fingers and the detent 6 is shifted downwardly with the thumb from the position of FIGURE 1 to the position shown in FIGURE 5. As described later in detail, upon being shifted downwardly, the detent permits the shiftable bracket to be pivoted outwardly to the position shown in broken lines in FIGURE 2 and in full lines in FIGURE 5 to unclamp the abrasive block 2.

Holder Construction Described in detail, the handle of the holder 1 preferably is fabricated from wood, although other materials may be utilized. The clamping brackets 4 and 5, in the example selected to illustrate the invention, are formed of sheet metal configurated to impart stifiness to the brackets.

The fixed bracket 4 (FIGURES 1 and 2), comprises a vertical limb 7 having a pair of spaced side flanges 88 which form a mounting head 9 straddling the handle 3. The bracket is attached rigidly to the handle 3 by a pair of rivets 101(l passing through the head 9 and through the end portion of the handle. Toward the lower end portion of the limb 7, the flanges 88 (FIGURE 1), are bent inwardly to overlie the internal surface of the limb, as indicated at 11, thus providing a double metal thickness. The lower end portion of the limb, including the inturned flanges, is bent at right angles to form a transverse key 12, which is engageable with the slotted end portion of the abrasive block 2, as described in detail later.

The shiftable clamping bracket 5 is generally similar to the fixed bracket 4, being formed from sheet metal and providing a vertical limb 13 (FIGURES 1 and 2) having side flanges 14-14. The side flanges of the upper portion of the bracket 5 provide a pivotal mounting head 15, the flanges of the head 15 straddling the flattened end portion 16 of the handle 3. The flanges at the lower portion of the limb 13 are folded inwardly as at 17 to reinforce the limb 13, as explained with reference to the fixed bracket 4. The lower end portion of the limb 13 is bent inwardly at right angles to provide a transverse key 18 which is engageable with the slotted end portion of the abrasive block 2, such that the block is clamped between the opposed keys 1 2 and 18, which project toward one another.

The mounting head portion 15 of the shittable bracket 5 is pivotally connected to the handle 3 by a rivet 19, which passes through the flanges of the head and through the flattened end portion 16 of the handle. This arrangement permits the shiftable bracket 5 to swing from the clamping position shown in full lines (FIGURE 2) to the unclamping position shown in broken lines in this view.

As noted above, the releasable latching detent previously indicated at 6, latches the shiftable bracket 5 in its clamping position and permits the bracket to be shifted to the unclamping position upon shifting the detent 6 downwardly. In the present disclosure, the latching detent 6 for-ms a part of a leaf spring 20. As viewed in FIGURE 2, the leaf spring is disposed beneath the handle 3 and its inner end portion is secured to the handle 3 by the wood screw 21, which is threaded into the handle.

The detent is generally triangular in shape, as viewed from the side (FIGURES 5-7) being formed by bending the end portion of the leaf spring 20 to the required angles. As shown in these views, the base of the triangular detent is formed by the leaf spring itself, and its upper inclined leg 22 is formed by bending an end portion of the leaf spring upwardly, at an angle. This provides the top surface of the detent, which is engaged by the thumb when the detent is shifted downwardly to its release position. The latching portion or leg of the detent is formed by bending the end portion of the inclined leg 22 downwardly, so as to provide the vertical leg 23 which is disposed at right angles to the leaf spring. In order to provide a camming action, the apex of the triangular detent, that is, the portion joining the

legs

22 and 23, is curved as at 24 to form a cam. As explained later, the curved cam 24 projects through an aperture formed in the shiftable bracket 5 for shifting the bracket to its clamping or unclarnping position.

As best shown in FIGURES 1, 3 and 4, the shiftablc bracket 5, immediately below its head portion 15, is provided with a rectangular aperture 25 which coacts with the releasable detent 6. The width of the aperture 25 is slightly greater than the width of the leaf spring 29 to provide clearance, adapting the left spring to shift vertically with respect to the aperture.

The detent 6 is somewhat wider than the aperture 25 to limit the outward pivotal motion of the shiftable bracket 5 to its unclamped position. Thus, as viewed in FIG- URES 4 and 5, the wider body portion of the detent 6 is delineated by the

shoulders

26 and 27 at opposite sides, which overhang the opposite sides of the aperture 25 and engage the outer surface of the link portion 13 of the shiftable bracket 5. The

shoulders

26 and 27 thus limit the outward motion of bracket 5 in the unclamping direction, with the detent depressed to the position indicated in FIGURE 5.

When one of the abrasive blocks is to be mounted in the holder 1, the detent 6 is first pressed downwardly to the position of FIGURE 5, allowing the clamping bracket 5 to be pivoted outwardly to its unclamping position. It will be noted in FIGURE 5, that the curved cam portion 24 seats against the upper edge 31 of the aperture 25, thereby frictionally holding the shiftable bracket 5 in its unclamped position. With the bracket 5 thus held in the unclamping position, the indexing keyway at the rearward end of the block 2, indicated generally at 28 in FIGURE 2 is engaged with the transverse key 12 of the fixed bracket 4. The forward end of the block 2 is then swung upwardly, as indicated by the broken lines in FIG- URE 2, to bring the indexing keyway of the forward end of the block, indicated generally at 38, into registry with the transverse key 18 of the shiftable bracket 5. At this point, the shiftable bracket is pivoted inwardly to bring its key 13 into engagement with the keyway 30.

It will be understood at this point, that the springloaded detent 6 acts automatically to apply clamping pressure to the shiftable bracket 5 by a wed ging action when the bracket is swung toward its clamping position, such that the block 2 is clamped under pressure by the shiftable bracket 5. During the initial pivotal motion of bracket 5 toward clamping position, as indicated by the arrows in FIGURE 6, the upper edge 31 of aperture 25 begins to slide across the curved cam surface 24 of the spring-loaded detent 6, thus adapting the detent to begin its upward motion toward the latching position. As the camming action progresses, the vertical leg 23 of the detent, which at this point is angularly related to the upper edge 31, begins to exert a wedging action with respect to the edge 31, as indicated by the broken lines in FIGURE 6. This wedging force increases progressively as the leg or latching portion 23 progressively shifts toward a vertical position during upward motion of the spring-loaded detent 6.

At the upper limit of travel of the detent, the latching portion or leg 23 reaches a vertical position parallel with the shiftable bracket 5, at which point maximum wedging action is imposed upon the bracket 5, thereby clamping the block 2 firmly between the fixed bracket 4 and shiftable bracket 5.

Abrasive Blocks As noted earlier, the several abrasive blocks illustrated in FIGURE 1 and FIGURES 8-13 are intended to be mounted in the tool holder to accommodate the contour of various work profiles which are to be finished or sanded by hand. Thus the abrasive block 2, shown in FIGURES 1, 2 and 11, is generally triangular in cross section, providing three flat abrasive surfaces 32, with a curved contour 33 joining the two adjacent sides of the triangular block. As explained later, the several abrasive surfaces may be presented to the work surface by indexing the abrasive block with respect to the holder.

In the example shown in FIGURE 8, the longitudinal abrasive surfaces of the block 34 consist of a combination of concave longitudinal grooves 35 and V-shaped grooves 36. The longitudinal contours of the block shown in FIGURE 9 include concave grooves 37-37 adapted to be utilized in finishing externally curved workpiece surfaces. The contours of the blocks shown in FIGURES 10, 12 and 13 also accommodate various work surfaces, the several contours being selectively shifted to the working position by indexing the block about its longitudinal axis with respect to the tool holder.

The abrasive blocks may be formed of wood or they may be formed of plastic or other appropriate material. The abrasive surface 38 of the blocks may consist of abrasive particles deposited directly upon the external surface of the block or it may be in the form of emery cloth or sand paper adhesively secured to the surface of the block. It will be understood that the blocks are furnished with various grades of abrasives, ranging from fine to coarse, depending upon the type of work for which any given block is designed.

In the several forms of abrasive blocks illustrated in the drawings, the indexing keyways, previously indicated at 28 and 30, comprise cross slots adapting the block to be indexed to four positions about its longitudinal axis with respect to the holder. Thus, as shown in FIGURES 813, each forward keyway 3t) comprises a horizontal slot til, bisected by a vertical slot 41. The rearward keyway 28 of each block is identical to the forward keyway 30.

As viewed in FIGURE 2, the

slots

40 and 41 are of equal depth, the depth of the slots being slightly less than the length of the

transverse keys

12 and 18 of the clamping brackets. Accordingly, the outer end of the keys l2 and 18 seat in pressure engagement against the inner ends 42-42 of the slots at opposite ends of the block. The slots preferably are dimensioned to interfit accurately the transverse keys l2 and 18 of the clamping brackets. This prevents any motion of the block about its horizontal axis with respect to the holder; moreover, the clamping pressure applied by the brackets aids in clamping the block rigidly with respect to the holder.

It will be understood that the horizontal and vertical slots 4i? and 41 are angularly related to the several abrasive surfaces 58 of the blocks, such that the selected surfaces are presented downwardly to the workpiece when the block is indexed with respect to the holder. It will also be understood that in the case of an abrasive block having but two abrasive surfaces, a single slot is formed in the opposite ends of the block to present the surfaces to the workpiece. It is also contemplated to provide abrasive blocks having a greater number of abrasive surfaces than those disclosed in the drawings, in which case the block will be provided with a number of indexing slots appropriate to the multiple abrasive surfaces of the block.

Having described my invention I claim:

1. An abrasive hand tool comprising, an abrasive block holder having a handle adapted to be gripped by the user, a fixed bracket attached to and extending downwardly from one end portion of the said handle, a shiftable bracket pivotally mounted upon and extending downwardly from the opposite end portion of the handle, said shiftable bracket adapted to be pivoted relative to the fixed bracket to a clamping or unclamping position, the outer end of each bracket including a key element, the key elements of said brackets projecting toward one another, latching means adapted to urge the said shiftable bracket toward the fixed bracket to a clamping position, and an abrasive block adapted to be mounted in said holder between said brackets, said abrasive block having v a plurality of abrasive surfaces and having respective indexing keyways at opposite ends related to the abrasive surfaces, said keyways adapted to be engaged by the key elements of the fixed and shiftable brackets, whereby the abrasive block is clampingly engaged between said brackets when the shiftable bracket is forced by said latching means to said clamping position toward the fixed bracket, said latching means being shiftable to a release position adapting the shiftable bracket to be moved to its unclamping position, the indexing keyways of the abrasive block adapting the block to be removed from said holder or to be indexed about the longitudinal axis thereof, whereby a selected abrasive surface of said block may be presented to a workpiece with the block clamped in said holder.

2. An abrasive hand tool comprising, an abrasive block holder having a handle adapted to be gripped by the user, a fixed bracket attached to and extending downwardly from one end portion of the said handle, a shiftable bracket having an upper end pivotally connected to said handle and extending downwardly from the opposite end portion of the handle and adapted to be pivoted relative to the fixed bracket to a clamping or unclarnping position, the outer end of each bracket including a key element, said key elements projecting toward one another, spring-loaded self-latching detent means connected to said handle, said detent means engageable with the shiftable bracket and adapted to latch the said shiftable bracket in a clamping position relative to the fixed bracket, and an abrasive block adapted to be releasably mounted in said holder between said brackets, said abrasive block having a plurality of abrasive surfaces and having respective indexing keyways at opposite ends related to the abrasive surfaces, said keyways adapted to be engaged by the key elements of the fixed and shiftable brackets, whereby the abrasive block is clampingly engaged between said brackets when the shiftable bracket is forced by said detent means to said clamping position toward the fixed bracket, said detent means being shiftable to a release position, adapting the shiftable bracket to be moved to its unclamping position, the indexing keyways of the abrasive block adapting the block to be removed from said holder or to be indexed about the longitudinal axis thereof upon being unclamped, whereby a selected abrasive surface of said block may be presented to a workpiece with the block clamped in said holder.

3. An abrasive hand tool comprising, an abrasive block holder having a handle adapted to be gripped by the user, a fixed bracket attached to and extending downwardly from one end portion of the said handle, a shiftable bracket pivotally mounted upon and extending downwardly from the opposite end portion of the handle and adapted to be pivoted relative to the fixed bracket to a clamping or unclamping position, the outer end of each bracket including a transverse key element, spring-loaded self-latching detent means connected to said handle, said detent means including a wedging surface engageable with the forward surface of the shiftable bracket, spring means adapted to urge the detent means in a wedging direction, whereby the detent means is adapted to urge the said shiftable bracket toward the fixed bracket in an automatic manner, and an abrasive block adapted to be releasably mounted in said holder between said brackets, said abrasive block having a plurality of abrasive surfaces and having respective indexing keyways at opposite ends related to the abrasive surfaces, said keyways adapted to be engaged by the transverse key elements of the fixed and shiftable brackets, whereby the abrasive block is clampingly engaged between said brackets when the shiftable bracket is wedged by said detent means to said clamping position toward the fixed bracket, said detent means being shiftable manually to a release position, adapting the shiftable bracket to be pivoted to its unclamping position, the indexing keyways of the abrasive block adapting the block to be released from said holder or to be in- 7 dexed about the longitudinal axis thereof upon being unclamped, whereby a selected abrasive surface of said block may be presented to a workpiece with the block clamped in said holder.

4. A holder for releasably clamping a series of interchangeable abrasive blocks in a working position relative to said holder, said abrasive blocks including keyways formed in the opposite ends thereof, said holder comprising, a handle adapted to be gripped by the user, a fixed bracket attached to and extending downwardly from one end portion of said handle, a shiftable bracket pivotally mounted upon and extending downwardly from the opposite end portion of the handle and adapted to be pivoted relative to the fixed bracket to a clamping or unclarnping position, a key element mounted on the lower end portion of each bracket and adapted to engage the keyways formed in the opposite ends of said interchangeable abrasive blocks, said shiftable bracket having an aperture formed therein including a transverse upper edge, a leaf spring having an inner end portion secured to said handle and having an outer end portion projecting through said aperture, a detent element mounted upon the outer end portion of the leaf spring, said detent element having a wedging surface which engages the transverse upper edge of said aperture, said leaf spring normally biasing said detent element upwardly with respect to said handle, whereby the wedging surface of the detent element engages the said upper edge and forces the shiftable bracket by wedging action toward the fixed bracket, thereby to provide a clamping engagement with the opposite ends of an abrasive block which is disposed between the fixed and movable brackets, said detent element adapted to be forced downwardly relative to the shiftable bracket counter to the leaf spring, adapting the bracket to pivot to an unclamping position, thereby to disengage the abrasive block with respect to said holder.

5. A holder for releasably clamping a series of interchangeable abrasive blocks in a working position relative to said holder, said abrasive blocks including keyways formed in the opposite ends thereof, said holder comprising, a handle adapted to be gripped by the user, a fixed bracket attached to and extending downwardly from one end portion of said handle, a shiftable bracket pivotally mounted upon and extending downwardly from the opposite end portion of the handle and adapted to be pivoted relative to the fixed bracket to a clamping or unclamping position, a key element mounted on the lower end portion of each bracket and adapted to engage the keyways formed in the opposite ends of said interchangeable abrasive blocks, said shiftable bracket having an aperture formed therein including a transverse upper edge, a leaf spring having an inner end portion secured to said handle and having an outer end portion projecting through said aperture, said leaf spring normally springing upwardly relative to said handle, the outer end portion of the leaf spring, which projects through the said aperture being bent to form an integral detent element, said detent element having a latching leg disposed generally at right angles to the plane of the leaf spring and providing a wedging surface with respect to the path of motion of the shiftable detent in response to the upward force imposed by said leaf spring, whereby said latching leg is adapted to provide a wedging engagement with respect to the transverse upper edge of the aperture, thereby to pivot the shiftable bracket toward said clamping position in an automatic manner.

6. A holder for releasably clamping a series of interchangeable abrasive blocks in a working position relative to said holder, said abrasive blocks including keyways formed in the opposite ends thereof, said holder comprising, a handle adapted to be gripped by the user, a fixed racket attached to and extending downwardly from one end portion of said handle, a shiftable bracket pivotally mounted upon and extending downwardly from the opposite end portion of the handle and adapted to be pivoted relative to the fixed bracket to a clamping or unclamping position, a key element mounted on the lower end portion of each bracket and adapted to engage the keyways formed in the opposite ends of said interchangeable abra sive blocks, said shiftable bracket having an aperture formed therein including a transverse upper edge, a leaf spring having an inner end portion secured to said handle and having an outer end portion projecting through said aperture, said leaf spring normally springing upwardly relative to said handle, the outer end portion of the leaf spring, which projects through the said aperture, being bent to form an integral detent element, said detent elcment having an outer leg extending upwardly from the outer end of the leaf spring and being inclined toward the outer surface of the shiftable bracket, the upper por tion of said outer leg being bent downwardly and forming a latching leg, said latching leg providing a wedging surface with respect to the path of motion of the shiftable detent in response to the upward force imposed by said leaf spring, whereby said latching leg is adapted to provide a wedging engagement with the transverse upper edge of said aperture, thereby to pivot the shiftable bracket toward said clamping position in an automatic manner.

References Cited in the file of this patent UNITED STATES PATENTS 199,261 Caden et a1 Ian. 15, 1878 219,391 Neal Sept. 9, 1879 2,529,434 Walker Nov. 7, 1950

Claims

1. AN ABRASIVE HAND TOOL COMPRISING, AN ABRASIVE BLOCK HOLDER HAVING A HANDLE ADAPTED TO BE GRIPPED BY THE USER, A FIXED BRACKET ATTACHED TO AND EXTENDING DOWNWARDLY FROM ONE END PORTION OF THE SAID HANDLE, A SHIFTABLE BRACKET PIVOTALLY MOUNTED UPON AND EXTENDING DOWNWARDLY FROM THE OPPOSITE END PORTION OF THE HANDLE, SAID SHIFTABLE BRACKET ADAPTED TO BE PIVOTED RELATIVE TO THE FIXED BRACKET TO A CLAMPING OR UNCLAMPING POSITION, THE OUTER END OF EACH BRACKET INCLUDING A KEY ELEMENT, THE KEY ELEMENTS OF SAID BRACKETS PROJECTING TOWARD ONE ANOTHER, LATCHING MEANS ADAPTED TO URGE THE SAID SHIFTABLE BRACKET TOWARD THE FIXED BRACKET TO A CLAMPING POSITION, AND AN ABRASIVE BLOCK ADAPTED TO BE MOUNTED IN SAID HOLDER BETWEEN SAID BRACKETS, SAID ABRASIVE BLOCK HAVING A PLURALITY OF ABRASIVE SURFACES AND HAVING RESPECTIVE INDEXING KEYWAYS AT OPPOSITE ENDS RELATED TO THE ABRASIVE SURFACES, SAID KEYWAYS ADAPTED TO BE ENGAGED BY THE KEY ELEMENTS OF THE FIXED AND SHIFTABLE BRACKETS, WHEREBY THE ABRASIVE BLOCK IS CLAMPINGLY ENGAGED BETWEEN SAID BRACKETS WHEN THE SHIFTABLE BRACKET IS FORCED BY SAID LATCHING MEANS TO SAID CLAMPING POSITION TOWARD THE FIXED BRACKET, SAID LATCHING MEANS BEING SHIFTABLE TO A RELEASE POSITION ADAPTING THE SHIFTABLE BRACKET TO BE MOVED TO ITS UNCLAMPING POSITION, THE INDEXING KEYWAYS OF THE ABRASIVE BLOCK ADAPTING THE BLOCK TO BE REMOVED FROM SAID HOLDER OR TO BE INDEXED ABOUT THE LONGITUDINAL AXIS THEREOF, WHEREBY A SELECTED ABRASIVE SURFACE OF SAID BLOCK MAY BE PRESENTED TO A WORKPIECE WITH THE BLOCK CLAMPED IN SAID HOLDER.