US3795077A

US3795077A - Segmental cut-off grinding wheel

Info

Publication number: US3795077A
Application number: US00311467A
Authority: US
Inventors: R Bosma; G Pettee
Original assignee: Norton Co
Current assignee: Saint Gobain Abrasives Inc
Priority date: 1972-12-04
Filing date: 1972-12-04
Publication date: 1974-03-05
Anticipated expiration: 1991-03-05

Abstract

A high speed segmental cut-off grinding wheel has a reusable drive center with either one or a plurality of angularly spaced narrow segment aligning grooves of predetermined radial depth in its circumferential surface and a plurality of identical interchangeable, replaceable and detachable composite abrasive segments equally spaced around the center. Each abrasive segment has a segment support member, including resilient members extending into the aligning groove, engaging the center, and displacing the segment radially outward into a precise position and engagement with a plurality of quickly and easily removable segment locating and retaining members, each with a locking groove therein, inserted into axially aligned mating apertures in the center and extending through non-aligned locating apertures in the displaced segment support member. Sufficiently displacing each abrasive segment inwardly relative to the center deflects and preloads the resilient members and aligns the previously nonaligned locating apertures with the axially aligned apertures in the center for either inserting or removing the locating and retaining member to replace a segment. The resilient members bias the released composite abrasive segment outwardly with sufficient force to maintain the segment support member engaged with precision locating surfaces within the locking grooves of the locating and retaining members and thereby prevent axial displacement of the segment locating and retaining members.

Description

Patent 1 osma et al.

1 Mar. 5, W741 l l SEGMENTAL CUT-OFF GRINDING WHEEL [75] Inventors: Robert W. Bosma, Whitinsville;

George H. Pette'e, Sterling, both of Mass.

Primary Examiner0thell M. Simpson Assistant Examiner-Marc R. Davidson Attorney, Agent, or Firm-Walter Fred {57] ABSTRACT A high speed segmental cut-off grinding wheel has a reusable drive center with either one or a plurality of angularly spaced narrow segment aligning grooves of predetermined radial depth in its circumferential surface and a plurality of identical interchangeable, replaceable and detachable composite abrasive segments equally spaced around the center. Each abrasive segment has a segment support member, including resilient members extending into the aligning groove, engaging the center, and displacing the segment radially outward into a precise position and engagement with a pluralityof quickly and easily removable segment locating and retaining members, each with a locking groove therein, inserted into axially aligned mating apertures in the center and extending through non-aligned locating apertures in the displaced segment support member. Slufi'iciently displacing each abrasive segment inwardly relative to the center deflects and preloacls the resilient members and aligns the previously non-aligned locating apertures with the axially aligned apertures in the center for either inserting or removing the locating and retaining member to replace a segment. The resilient members bias the released composite abrasive segment outwardly with sufficient force to maintain the segment support member engaged with precision locating surfaces within the locking grooves of the locating and retaining members and thereby prevent axial displacement of the segment locating and retaining members.

17 Claims, 9 Drawing Figures PATENTEU 5 4 SHEET 1 BF 2 1 SEGMENTAL CUT-OFF GRINDING WHEEL BACKGROUND OF THE INVENTION 1. Field of Invention The invention relates to relatively large high speed segmental cut-off grinding wheels with unique means for attaching and detaching a plurality of identical easily and quickly detachable, and interchangeable composite abrasive segments thereon.

2. Description of the Prior Art Heretofore, abrasive segments have been attached to relatively small diameter and seldom reused drive hubs or centers by riveting, bolting, brazing and adhesively bonding them to the center. Thus, a great deal of time and effort. is required to replace worn out segments with new ones. The applicants segmental cut-off wheel differs from the prior art in that the abrasive segments can be replaced quickly, and are continually biased outwardly, by preload resilient members into a precise position determined by engagement with a plurality of easily and quickly removable segment locating and retaining members locked to and unlocked from a reusable center by radially displacing the abrasive segment and its support member situated within a peripheral groove in the center respectively into and out ofa locking groove in the segment locating and retaining members.

1 Similar segmental cut-off grinding wheels are disclosed in copending applications of Joseph J. Patemo, Ser. No. 294,083 filed Oct. 2, I972 and Loring Coes, Jr. Ser. No. 302,662 filed Nov. 1, 1972 and to which reference may be had for details not disclosed herein.

Also, in US. Pat. Nos. 23,7,472 issued to Blackburn,

Feb. 8, 188 l; 3, l 62,187 issued to ChristensomDec. 22, 1964; 2,092,591 issued to Sohlstrom, Sept. 7, 1937; German PatfNos. 530,792 issued to Krug, July 23, 1931', and 1,652,883 issued to Berstecheron Mar 11, I971 there are disclosed various prior art grinding wheels of which the applicants are aware that are similar to but clearly distinguishable from the invention disclosed hcreinbelow.

SUMMARY OF THE INVENTION The invention relates to a high speed segmental cutoff grinding wheel of relatively large diameter with a thin reusable drive center or hub adapted with suitable means by which it'ean be mounted on an arbor and rotatably driven about an axis in the conventional man ner. The thin drive center may have one or more narrow peripheral slots or grooves spaced circumferentially around the center and recessed radially inward from a peripheral surface extending between opposite sides of the center, a predetermined radial depth to a bottom surface, at the bottom of the groove, extending axially between opposed spaced flange portions of the center. There are a plurality of identical groups of axially aligned apertures of identical size and shape equally spaced around and extending axially through the opposed spaced flange portions with the axes of the apertures situated on a first base circle ofpredetermined radius from the axis of the center. A plurality of identical interchangeable, displaceable, replaceable, and detachable arcuate composite abrasive segments are equally spaced around and resiliently displaced radially outward relative to the center, each having, a thin segment base or support member with a perforated outer radial portion embedded in, interlocked with and 2 resin bonded to a thicker arcuate resin bonded abrasive portion or member and an inner radial portion or tongue portion projecting symmetrically therefrom into the groove between the opposed spaced flange portions of the center, The tongue portion has a plurality of identical segment locating apertures substantially identical in size, shape and spacing between their axes to the apertures in the flange portions and which have axes radially displaced to position situated and spaced on a second base circle of greater radius from the axis than the first mentioned base circle of predetermined radius when in the final grinding or cutting position.

There are preloaded resilient means engaging the bottom surface and biasing the segmcnts radially outward relative to the center into engagement with a plurality of segment locating and retaining members of identical size and shape extending axially through the nonaligned segment locating apertures in the thin segment base member into'the axially aligned apertures in the spaced side flange portions of the center. Each segment locating and retaining member has intermediate its ends, a locking groove, including a segment locating surface therein, of predetermined depth and of substantially the sameaxial, width as the groove between the flanges.

The composite abrasive segments are either removed from or attached to the center by forcing and displacing the composite segment radially inward toward the axis to further deflect or compress and preload the resilient means against the bottom surface until the segment locating aperture in the segment base member is aligned with the apertures in the flange portions after which the segment locating and retaining members are shifted axiallysufflciently to remove and attach a segment to the center. A composite abrasive segment is locked to and precisely located relative to the center upon releasing the segment which allows the preloaded resilient means to bias the segment base member outwardly into the lockinggroove and engagement with the locating surface within the locking groove on the segment locating and retaining members which as a result are trapped or locked in place and prevented from being displaced axially by engagement with the segment base member engaging the center. The resilient means are preferably an integral part of a segment base member with inclined diverging inner surfaces of the tongue portion engaging the surface at the bottomof the groove. A slot extends a predetermined depth from each radial end of the tongue portion and adjacent to each of the diverging inner surfaces whereby a pair of defleetable elongated cantilever springs are provided for and resiliently engaging the bottom surface of the groove in the center.

Therefore, it is the primary object of the invention to provide a segmental cut-off grinding wheel having a thin reusable center including one or more peripheral segment aligning grooves into which extend support members ofa plurality of identical interchangeable, replaceable and detachable reinforced composite abrasive segments continually forced radially outward, by resilient members, into locking engagement with segment locating and retaining members quickly unlocked and easily removed from the center by radially displacing the abrasive segme nts inwardly to attach and detach the abrasive segments to and from the center.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view of an assembled segmental cut-off grinding wheel of the invention,

FIG. 2 is an enlarged cross sectional view taken on line 2-2 of FIG. 1, through one of the abrasive segments and a portion of the center to show how the abrasive segment is constructed and attached to the drive center,

FIG. 3 is a fragmentary cross sectional view through a side portion of one .embodiment of the cut-off grinding wheel of the invention showing .a side of one embodiment of the arcuate abrasive segments resiliently mounted around a center with a continuous groove therein,

FIG. 4 is an enlarged cross sectional view through the locking groove in one of the segment locating and retaining members and showing the engaging locking portion of a segment support member located around and displaced radially into the locking groove to prevent axial displacement of the retaining member,

FIG. 5 is a fragmentary cross sectional view of a seg mental cut-off grinding wheel showing another embodiment of the invention wherein there are a plurality of grooves angularly spaced in the'center and abrasive segments with segment support members inserted therein of another configuration adapted thereto, v

FIG. 6 is a fragmentary cross sectional View showing another embodiment of a segment locating and retaining member with chamfered aligning surfaces on opposite sides of the locking groove engaged and aligned by the segment support member,

FIG. 7 is a fragmentary cross sectional view showing another embodiment of .a segment support member with a double chamfered segment locating aperturefor aligning a generally U-shaped rectangular locking groove in the segment locating and retaining member therewith,

FIG. 8 is a fragmentary cross sectional view showing another embodiment of a segment locating and retaining member with V-shaped segment locating surfaces and locking grooves aligned by the engaging double chamfered surfaces of a segment support member with a double chamfered locating hole, and

FIG: 9 is a fragmentary cross sectional view showing another embodiment of a segment locating and retaining member with a modified form of a substantially V- shape locking groove and locating surfaces engaged and aligned by a segment support member with straight non-beveled locating apertures.-

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) Referring to FIGS. 1, 2 and 6 there is shown a segmental cut-off grinding wheel 10 of relatively large diameter which may be anywhere between 2 to 6 feet and have an axial thickness of between one/fourth to three/fourths of an inch. The wheel 10 comprises a thin rotatable, reusable, drive cylinder, center, disc or hub 12 with suitable means, such as, a center hole 12a, for mounting the wheel 10 on a suitable rotatably driven spindle of a cut-off machine. As shown, the reusable drive center 12 is generally of circular shape and has opposite sides or surfaces 12!) and 120 extending radially outward from the center hole, about the axis of the center, to a peripheral or circumferential surface 12d of the center. Extending radially inward from the peripheral surface 12d there may be one or more narrow segment aligning grooves 122 of predetermined substantially uniform axial width of between 0.040 0.375 of an inch located between and at substantially equal distance from the opposite sides. As shown in FIGS. 3 and 6, the narrow aligning groove 126 may be one which extends either continuously around or one of a plurality of identical grooves angularly spaced around the center and extending a predetermined substantially uniform radial depth ofbet'ween l 4 inches to a circular or straight bottom surface 1211 of predetermined diameter or radius, from the axis at the bottom of the groove ,which separates and provides a pair or set of axially spaced opposed. side flange portions 12f and 12g on the center. Preferably, the center is a steel disc which may be made out of conventional saw steel and pretensioned in the conventional way as by' rolling or peening to stiffen and increase its rigidity. Through the

side flange portions

12f and 12;; are a plurality of equally spaced groups of axially aligned apertures 12] and segment locating and retaining members 14 slideably-mounted therein of substantial identical size and shape with the axes of each group of members and apertures spaced on a first base circle be of predetermined radius or diameter.

The segment locating and retaining member 14 has an axial thickness or length no greater than that of the center 12, and a locking groove 14a and segment locating surface 14b therein of predetermined radial depth and axial width, substantially the same as the narrow aligning groove 122. The locking groove 14a is located substantially equal distances from its opposite ends and between opposing sides of spaced flange or

end portions

14c and 14d of the member 14 engaging the center 12 within the apertures 12]. The members 14 have peripheral edges at its opposite ends and opposing sides of the groove 14a smoothed and slightly rounded off for guiding them into proper engagement with the other cooperating elements of the wheel.

Mounted on, equally spaced around and secured to the reusable hub or drive center 12 are a plurality of identical interchangeable and replaceable composite resin bonded abrasive segments 30 inserted into one or more grooves l2e. Each composite segment 30 comprises a thin segment base member or shoe 32 with an outer or upper radial portion 32a embedded in, interlocked with and resin bonded to the lower central portion of an abrasive portion, member or element 34. In some instances the abrasive segments are strong enough and do not require additional reinforcement. However, if necessary or preferred at least one layer of reinforcing material 36 may be bonded to a side of the base member and extends radially through the abrasive portion 34 bonded thereto, to the outer circular peripheral or circumferential surface of the composite segments 34 and grinding-wheel 10. The segment base member 32 may be either a one piece or-a laminated structure of suitable high strength material, for example, metal, plastic, reinforced plastic, and fiber glass.

The segment base member as shown in FIG. 2 and 3 is an arcuate or fan shape piece ofmetal selected from a group consisting of spring steel but may be a laminated structure made of resin bonded layers of either open or closed mesh fiber glass cloth or fiber glass woven roving as disclosed in the above mentioned copending application to which reference may be had for details not disclosed herein. The metal segment base member 32 has on its upper radial portion 32a means for interlocking the abrasive portion or member 34 thereto comprising a plurality of apertures or holes 32b through which the resin bonded abrasive material extends'and interconnects opposite sides of the abrasive member 34. Projecting radially inward from the under side or inner side and smallest radius of the arcuate abrasive portion 34 is a lower segment mounting porequal distances fromthe opposite radial end surfaces or edges of the tongue portion but displaced radially to positions at a greater radial distance from the axis and onto a second base circle of larger diameter than the first base circle on which the equallyspaced groups of apertures ll2j are situated.

Resilient means are provided for biasing the segment base member and the abrasive portionfix'ed thereto radially outward relative to the center 12 to the second base circle po'sition.- Preferably the resilient means comprises a plurality of 'deflectable cantilever type springs or resilient'members 32g and 32hintegral with and formed in the lower portion of the tongue, portion 320 on which there is a pair of inclined inner surfaces or diverging inner surfaces or edges for engaging the circular or bottom surface 12h at the bottom of the groove 12e in the center. There are'also a pair of elongated slots 321. and 32m, situated a predetermined distance from the diverging surfaces to provide a cantilever spring member of sufficient width and strength which upon being deflected and preloaded thereby will force and maintain the abrasive segment base member I in locking engagement with the locating surface 14b in thelocking groove 14a and side surfaces of the flange. 14c and 14d of the segment locating and retaining.

member 14. The slots 32L and 32m must also be of sufficient predetermined width to provide enough room for deflecting the springs 32 sufficiently to axially align the locating aperture 32din the segment base member 32 with the apertures 12j..When aligned, the. tongue portion 320 of member .32 is out ofthelocking groove 6 merits in a precise position anddriving engagement with the segment locating and retaining members 14.

The force exerted by the cantilever springsmust be greater than the weight of the segments so that the apertures cannot align and allow the escape of the members 14 when the wheel 10 is at rest.

Alternatively, more than two segment locating members 14 can be used to attach an abrasive segment and the geometrical shape of the member 14 and apertures l2j and. 32a'can be varied. For example, triangular, square, hexagonal, octan'gular and other non-circular cross sections can be used and would be more resistant to turning than the more economic easily formed circular or cylindrical shape disclosed.

A number of ways of providing resilient members integral with the segment member as well as those which are separate therefrom or integral with the center are possible. For example, the integral diverging cantilever v springs .could be separated from the segment support 7 member by cutting throughthe section connecting the slots 32L and 32m and thereby provide a separate preloaded leaf spring between the surface 12h andtongue of the segment support member 32c. Abrasive portion 34 of the segment can be made by molding it to the desired shape or preforming and bonding together suitable layers of an abrasive mix or mixture containing at least abrasive particles and a rcsinoid bonding material springs-32g and Big/tan amount greater than the depth of the locking groove 14. As a result, the displacement preloads the resilient springs sufficiently toprovide a sufficient amount of reserve force which upon releasing the segment 30, displaces the segment base member outwardly into the locking groove 14a and precise locating engagement with the segment locating surface 14!; and prevent axial displacement of the member 14. During high speed rotation and grinding or cutting with the wheel 10, centrifugal force being greater than the opposing grinding forces continues to maintain the'segsuch as a thermosetting phenolic resin. The abrasive particles may be natural or synthetic diamond, metal oxide, and carbide materials such as alumina, aluminazirconia, silicon carbide, boron carbide, tungsten car bide, and mixtures thereof."

The composite segment 30 can be made in various ways but. the preferred method is to simultaneously 'moldand bond the abrasive mix, the layer or layers of reinforcing material, and the upper portion 32a of a preformed segment base member. together to the desired size and shape determined by the mold. For example, a typical conventional mold may have a mold cavity of the desired arcuate shape, depth and thickness of the abrasive portion 34 and means to precisely position and support the preformed segment base member 32 with or without the locating holes 32d predrilled therein so the outer radial portion 32a projects the desired distance into the cavity. First an outer layer of the abrasive mix of predetermining depth to form an outer side portion of the abrasive porno-n34 is spread upon the bottom of the mold cavityflf two pieces of reinforcement are desired, one preformed piece of reinforcing material cut-out of a sheet of Lewcott No. 35 open mesh woven roving fiber glasscloth precoated wth like resinoid bonding material commercially available from Lewcott Chemical and Plastic Corporation,

Millbury, Mass, is placed on the loose layer of mix.

space and form the central or inner layer between the outer edge of the segment base member and the mold wall and the interlocking holes 32b if present. Thereafter, either a final outer layer of abrasive mix is spread thereoverv or a second piece of preformed reinforcing glass cloth is first laid over the central or inner layer and a side of .portion 32a followed by spreading a final outer layer of the abrasive mix thereover. The mold cavity is then closed with a suitable mold pressing plate and the mold placed between heatable platens ofa conventional hot press, where the abrasive mix, including the resin bond, the reinforcement and the segment base member are not pressed and resin bonded into a unitary composite segment of the desired size and shape at a pressure of /2 to 1 ton per square inch and temperature of 165C for 15 minutes.

The hot pressed composite segment is then stripped or removed from the mold and placed in an oven for a predetermined period of time at a predetermined temperature to thoroughly cure the thermosetting resin bond. The locating holes 32d may be machined in the preformed segment support 32 before molding or after the molded segment is cured, by placing it in a suitable precision drill jig or fixture for locating and drilling the segment locating holes 32d. When the holes 32d are predrilled the mold obviously has means, such as, locating pins to properly position the holes 32d.

Alternatively, the abrasive segment 30 may have lam inated fiber glass segment support members 32 and made by either hot or cold pressing the components together and curing the resin in the manner disclosed in the above mentioned copending applications to which reference may be had for details including an example of a suitable abrasive mixture not disclosed herein.

Another embodiment of the invention is disclosed in FIG. 5 which is a partial cross sectional view through a portion of a segmental cut-off wheel comprising a circular drive center 12 with a plurality ofidentical narrow segment aligning grooves, pockets or slots 12a of relatively short arcuate length angularly spaced, substantially equally around the peripheral or circumferential surface 12a. Between and separating the narrow grooves l2e are a plurality of ties, spacers or connecting webs 12w which may be separate elements fixed to but preferably formed integrally with the center 12 extending axially between the opposite sides 12b and 126 and a plurality of sets or pairs of opposed spaced side flange portions 12g and 12f angularly spaced thereby around the center 12. In this embodiment each of the grooves 126 extend a predetermined radial depth from the peripheral surface 121] to the bottom surface 1211 of predetermined radial distance from the axis of the center. The bottom surface 1212 is substantially straight, extends between and connected to two opposite concave or curved radial end surfaces 12y of adjacent spacers or webs 12w at the angularly spaced ends of the groove. Each curved side or end surface 12y has a portion with a curvature of predetermined radius determined by the diameter of the rotary cutter used to machine the slots in the center and extend from'the bottom surface 12h to the peripheral surface 12d.

Inserted into each of the spaced grooves 120 is an abrasive segment 30 which differs from the segment 30 shown in FIG. 3 only in the configuration of the tongue portion 320. As shown the tongue portion 320 of the segment support member 32 has a configuration similar to and adapted to fit the groove, and convex or curved shaped radial end surfaces 32r spaced from the concave surfaces 12y of the webs 12w, engaging cantilever springs 32g and 32h ofshorter length than those shown in FIG. 3. In effect each of the opposite radial end corner portions of the tongue portion 32c of the segment shown in FIG. 3 has been removed and rounded off to provide the abrasive segment 30 shown in FIG. 5. As a result the cantilever springs are slightly stiffer and thereby displaces the segment support member with slightly greater force radially into engagement with the locating surface 141) of the segment locating and retaining members 14. However, it is obvious that the dimension of the cantilever springs can be modified to either increase or decrease the amount of force exerted thereby.

Except for the modifications described above the abrasive segments 30 and center 12 shown in FIG. 5 are identical in every other respect to the segment 30 and center 12 shown in FIG. 3 and attached and detached to and from the center 12 in the same manner described above.

Various embodiments of aligning guide means for the segment locating and retaining means 14 are shown in FIG. 6 through 9 inclusive and which guide means provide for more positively aligning the locking groove with the segment support member and the center.

In FIG. 6 there is shown a modified form ofa segment locating and retaining member 14 which differs from the one shown in FIG. 2 in that it has a tapered, beveled or chamfered surface 14! extending between each of the side surfaces 14c and 14d and the peripheral surface instead of and replacing the corner formerly at the junction thereof. The chamfers, tapers or bevels 141 of a misaligned member 14 may be engaged by corners of the segment support member at opposite ends of the locating aperture 32d and thereby axially shift the member 14 sufficiently to allow the segment support member 32 into the generally U-shaped rectangular locking groove 14a, locating engagement with the locating surface 14h, locking engagement with the side surfaces 140 and 14d, and to positively align and/or center the retaining member 14 with the center 12.

In FIG. 7 there is shown a portion of the tongue portion 32c ofa segment support member modified to provide tapered, chamfered or beveled surfaces 321 at opposite ends of the locating aperture 32d. The chamfers or bevels or tapers 32; extend from the internal locating surface of the aperture 32d to each opposite side or surface of the segment support member 32 and replace corners formerly at the junction thereof. In this instant the incline surface of the chamfers 32; may engage the corners at thejunction of the

sides

14c and 14d with the peripheral surface thereon and thereby axially shift a misaligned locking groove and member 14 into alignment with the segment support member 32 and the center 12.

Another version 'of a segment locating and retaining member 14 is shown in FIG. 8 having both a V-shape locking groove and locating surfaces 14v adapted for mating locating and locking engagement with the mating inclined surfaces, tapers, bevels or chamfers 32! at opposite ends of the locating aperture 32d. The locating V-shape groove 14v is of substantially the same axial width as the groove 12: and a misaligned member 14 is axially shifted by the forceful engagement of the surfaces of the taper or chamfer 32t with the \/-shape locking surfaces 14v.

Another generally V-shape segment locking groove and locating surfaces 141: connected by a concave surface at the bottom of the groove and of greater axial width than the groove 12e in the center 12 and thickness of the engaging tongue portion 320 of a segment support member 32 with a straight non-chamfered locating aperture and internal surface 32d therein extending between the opposite sides thereof.

- As used herein, a'generally U-shape rectangular locking groove, is intended to also include and define a groove formed by removing a portion of substantially square or rectangular cross section from the member 14 and with the

sides

14c, 14d at substantially right angles to the locating surface 14b.

The preloaded cantilever springs force the corners or edges at opposite ends of the apertures 32d in the tongue into engagement'with the V-shape surface l4u and thereby axially shifts the member 14, precisely locates the segment support member 32 relative to the center and locks the member 14 against any further axial displacement.

Identical arcuate composite abrasive segments 30 with segment support members made from C-1075 hard cold rolled spring steel with a hardness of between C22 and C33 measured on the Rockwell scale embedded approximately 1 inch into the abrasive portions 34 and with'precise dimensions necessary to make them 'engage a bottom surface 12h 9% inches in radius from the axis of a stainless steel center 1 1-15/32 inches in radius. The abrasive section 34 being /4 of an inch in axial thickness X 4 inches in radial width or depth and the tongue portion 32c 0.050 of an inch thick and varying to approximately 2 inches in radial depth with the abrasive section 34 overhanging the sides of the tongue equally, approximately 0.100 of an inch and with included angle of approximately 35 between the radial ends or edges.

Excess cured thermosetting phenolic resin flash or material is removed from the precisely formed composite segment. Each segment member 32 has two 0.625 of an inch diameter segment locating apertures machined therein with their axes spaced 3.375 of an inch between centers measured on a chord 10.494 inches from the axis ofa base circle or are with a radius of ap proxirriately -11/16 inches (21% inch in diameter) with the axes of the end holes substantially equal distances from the radial ends or edges of the segment and from each of .a pair of radial planes spaced 36 apart passing between adjacent segments 30 of the grinding wheel 10. Both of the opposite edges, corners, or end surfaces of theapertures 32d and l2j are smoothed or rounded off to remove any burrs which prevent insertion of the retaining member The composite segments 30 are preferably of shorter arcuate length than the length of an are extending between each pair of radial planes spaced at, predetermined equal angles of 36 around the axis of the hub 12. Thus when mounted on the hub 12 the segments 30 will be spaced'from one another and have a space in this specific embodiment of about one/fourth of an inch.

Ten interchangeable composite abrasive segments 30 of the dimensions given above are then mounted on a one piece reusable steel drive center or hub 12 with the following approximate dimensions: outside diameter of 22-15/16 inches, axial thickness of 0.200 of an inch, a center hole 4 inches in diameter, one or a plurality of angularly spaced segment aligning grooves 0.053 of an inch wide by 1-31/32 inches in radial depth either to a circular surface or bottom surface 9 /2 inches in radius from the axis at bottom of the groove. There are 10 equally spaced identical groups of two apertures each or a total of 20 apertures 0.626 of an inch in diameter and 20 segment locating and retaining member 0.621 of an inch in diameter by 0.200 of an inch long with a central locking groove 0.053 of an inch wide by 0.032 of an inch deep in the apertures with the axes of each group of apertures spaced 3.375 inches measured on a chord 10.494 inches from the axis ofa base or bolt circle be approximately 10-1 1/16 inches in radius and 21% inches in diameter.

When the composite abrasive segments 32 are assembled on the hub of the dimensions described above, by example only, and radially displaced outwardly one thirty-second of an inch relative thereto by the pre' loaded resilient springs, they produce a segmental cutoff grinding wheel with an outside diameter of 3 l -l/l 6 inches, 10 equally spaced abrasive: segments 0.250 of an inch thick with sides lying in a single plane about and normal to its axis of rotation and with a center hole 4 inches in diameter. The axes of each group of segment locating apertures in the tongue portions are like wise displaced 0.032 of an inch'or the amount equal to the depth of the locking groove from the axes of the group of apertures in the center spaced 3.375 inches apart measured on a chord 10.494 inches from the axis of a base circle be approximately 10-1 1/1, 6 inches in radius. Hence, the new or displaced positions of the apertures place their axes to lie 3.375 inches apart measured on a chord 10.526 inches from the axis of the center and on a base circle be of a greater radius of approximately 10-23/32 inches from the axis of the center. When the segments 30 have but one reinforcing member 36, the segments are preferably assembled so that the reinforcing'members of adjacent segments are staggered and alternately shifted from a position adjacent one side of the wheel to a position adjacent the opposite side. Hence all the reinforcement, does not lie in a single non abrading plane but is interrupted by at least one but preferably by a plurality of abrading portions of adjacent segments.

During rotation and forcing the segmental cutoff wheel to cut or grind through material, centrifugal force greatly exceeds the applied cutting or grinding forces required by an order of magnitude of approximately 10 to 1. Therefore, the greater outward force prevents the abrasive segments from being displaced inwardly, thereby maintaining the segment support member 32 within the locking groove and locking the members 14 to the center 12.

Obviously, larger segmental cut-off wheels than the specific examples of the invention given above can be made by modifying the dimensions of the segments and the hub to accommodate greaternumbers of composite segments required to complete the wheel of greater diameter and circumference. Also, the number and diameter of the segment locating and retaining member may be varied so long as there is sufficient strength in the total sectional area thereof to effectively oppose the calculated centrifugal load or force exerted by each abrasive segment rotating at the desired predetermined number of surface feet per minute.

Although the invention has been illustrated and described in specific embodiments, it is to be understood that many variations of and changes may be made therein without departing from the invention set forth in the following claims.

What is claimed is: 1. A relatively large segmental cut-off grinding wheel comprising:

a relatively large,- thin reusable drive center rotatable about its axis having a peripheral surface, opposite sides extending to the peripheral surface, at least one narrow segment aligning groove of predetermined axial width extending inwardly from the peripheral surface a predetermined radial depth to a bottom surface extending axially between opposing inner sides of opposed'spaeed side flangeportions of the center, a plurality of axially aligned apertures of predetermined size and shape extending axially through the side flange portions with axes situated and spaced on a first base circle of predetermined radius from the axis; I I a plurality of interchangeable and replaceable composite abrasive segments mounted around',--attached to, and displaceable radially relative to the center, each'having a bonded abrasive portion of predetermined axial thickness, a segment base member having an outer radial portion fixed to an innerradial portion of the abrasive portion, a tongue portion, radially displaceable relative to the center, extending radially inwardly from the abrasive portion and slideably into the narrow seg-* ment aligning groove, a plurality of segment locating apertures, in the tongue portion of substantially the predetermined size. shape and spacing between their axes the axially aligned apertures in the'opposed spaced side flange portions and displaced radially so their axes lie substantially on a second base circle of greater radius than the first base circle of predetermined radius from the axis of the center; I

a pl urality of axially movable segment locating and retaining members slideably mounted within the axially aligned apertures in the side flange portions of the center and extending axially through the locating apertures in the segment support member radially displaced into engagement thcrewithand each having v a locking groove, including a segment locating surface engaged by the displaced segment support member therein, of predetermined depth between opposing inner side of spaced end portions of the segment locating and retaining member; and resilient means engaging the center for biasing and displacing each of the segment support members radially outward relative to the center into engagement with the segment locating surface in the locking groove and maintaining the abrasive segments in a precise radial position on the center, whereby the segment locating and retaining members are engaged, locked in place, and prevented from shifting axially by engaging portions of the segment support members biased into the locking groove and the abrasive segments may be quickly attached and detached from the center by radially displacing them inwardly against the resilient means sufficiently to shift the axes of the locating aperture from positions on the second base circle into axial alignment with the axes of the apertures in the side flange portions situated on the first base circle, and the segment support member out of the locking groove therein and sufficiently displacing the segment locating and retaining members axially relative to the center.

2;A segmental cut-off grinding wheel according to claim 1 wherein the resilient means comprises:

a pair of cantiliver spring members on the tongue portion of the segment support member each having an end portion anchored to a lower portion of the tongue portion; and

'an'elongated deflectable portion extending longitudinally from the anchored end portion, displaced into forceful engagement with the center within the narrow aligning groove sufficiently to exert a force necessary to displace and maintain the segment'support member radially outward against 1 the segment locating and retaining members.

3. 'A segmental cut-off grinding wheel according to claim'2 wherein the cantilever spring members are an integral part of each segment support member comprisa pair of the narrow elongated deflectablc portions lextending longitudinally in opposite directions from a central lower anchor portion of the tongue portionalong and including the lower inner edge of the tongue portion toward opposite radial ends of E the*tongue portion and displaced into engagement -With the center within the narrow groove; and

apair of elongated slots adjoining the deflectable portions and extending a predetermined depth from'the opposite radial ends of the tongue por tion.

4. A segmental cut-off grinding wheel according to claim 1 wherein the center has one continuous narrow segment aligning groove extending circumferentially around the center and into whicheach of the segment support members are slideably mounted, and wherein the plurality of axially aligned apertures are arranged into a pluralityof groups equally spaced around the center, each group having aligned apertures with their axes situated and spaced on the first base circle, extending axially through the spaced opposed side flange portions.

5. A segmental cut-off grinding wheel according to claim 1 wherein the center has a plurality of narrow segment aligning grooves of pre determined arcuate length angularly spaced around the center and extending radially inward from the peripheral surface a predetermined radial depth to bottom surfaces extending axially between opposing inner sides of a plurality of angularly spaced sets of spaced opposed side flange portions of the center;

a plurality of spacers extending radially between and separating the plurality of narrow segment aligning grooves and sets of the spaced opposed side flange portions; and

an identical number of at least two of the axially the tongue portion have wherein the plurality of axially aligned apertures are arranged into a plurality of groups equally spaced around the center, each group having an identical number of at least two of the axially aligned apertures, with their axes situated and spaced on the first basecircle, extending axially through each set of the plurality of angular spaced sets of the spaced opposed side flange portions of the center. 6. A relatively large segmental cut-off grinding wheel according to claim wherein the spacers between the segment aligning grooves are an integral part of the center and have curved, side surfaces of predetermined curvature at opposite angularly spaced radial ends of the narrow aligning grooves extending from the bottom sur faces to the peripheral surface of the center and defining the configuration of the narrow segment aligning groove; and I wherein the tongue portion of the segment support members have curved radial edges spaced from and corresponding substantially to the curvature of the curved side surfaces; and

a configuration corresponding substantially to the configuration of the narrow aligning grooves.

7. A relatively large segmental cut-off grinding wheel according to claim 1 wherein the locating aperturesin substantially straight internal locating surfaces extending between opposite ends and edges thereof at opposite sides of the tongue portion; and wherein the segment locating. and retaining member may selectively have generally U-shape rectangular locking grooves and V-shape locking grooves and locating surfaces for selectively engaging the straight internal locating surfaces and the edges of the locating apertures.

8. A relatively large segmental cut-off grinding wheel according to claim 1 further comprising guide means, including portions of the tongue portion at opposite ends of the locating apertures and portions of opposing inner sides of the locking groove, for engaging one another and aligning the locking groove in the segment locating and retaining members with the tongue portion.

9. A relatively large segmental cutoff grinding wheel according to claim 8 wherein the guide means comprises: r

beveled surfaces in the portion of the tongue portion at opposite ends of the locating apertures in the tongue portion.

10. A relatively large segmental cut-off wheel according to claim 9 wherein the segment locating and retaining members have V-shape locking grooves and locating surfaces adapted for mating locating and locking engagement with the beveled surfaces at opposite ends of the locating apertures in the tongue portion.

ll. An interchangeable and replaceable composite abrasive segment adapted to be mounted around, attached to, and displaceable radially relative to a relatively large thin reusable rotatable drive center having an axis, at least one narrow segment aligning groove of predetermined axial width extending inwardly from a peripheral surface a predetermined radial depth to a bottom surface extending axially between opposing inner sides of opposed spaced side flange portions of the center, a plurality of axially movable segment locating and retaining members, each with a segment locking groove and locating surfaces therein between opposing inner sides of spaced end portions thereon slideably mounted within axially aligned apertures in the side flange portions of the center with axes situated and spaced on a first base circle of predetermined radius from the axis and the composite abrasive segment com prising:

a bonded abrasive portion of predetermined axial thickness;

a segment base member having an outer radial portion fixed to an inner radial portion of the abrasive portion, a tongue portion ex tending radially inwardly from the abrasive portion adapted to be inserted and slideable into both the segment aligning groove and the locking groove and displaced radially into locking and locating engagementwith the locating surface in the segment locating and retaining members in the center, a plurality of segment locating aper tures and locating surfaces in the tongue portion of substantially the size, shape and spacing between their axes on the first circle the axially aligned apertures in the opposed spaced side flange portions and through which the segment locating and retaining members and engage the locating surfaces in the tongue portion; and resilient means, on the tongue portion, for forcefully engaging the center within the segment aligning groove preloaded by displacing the abrasive segment sufficiently to align the locating and axially aligned apertures and inserting the segment locating and retaining members therein and upon releasing the abrasive segments for biasing and radially displacing the tongue portion outwardly relative to the center into the locking groove to maintain the locating surface of the tongue. portion in locating engagement with the locating surface of the segment locating and retaining members which are thereby locked in place against axial movement relative to the center and shift the axes of the locating apertures to positions on a second base circle of greater radius from the axis of the center.

12. An interchangeable and replaceable composite abrasive segment according to claim 11 wherein the resilient means comprises:

a pair of cantilever spring members on the tongue portion of the segment support member each having an end portion anchored to a lower portion of the tongue portion; and

an elongated deflectable portion extending longitua pair of narrow elongated deflectable portions ex-' tending longitudinally in opposite directions from a central lower anchor portion of the tongue portongue portion further comprises:

tion along and including the lower inner edge of the tongue portion toward opposite radial ends of the tongue portion and displaced into engagement with the center within the narrow groove; and a pair of elongated slots adjoining the deflectable portion and extending a predetermined depth from the opbeveled locating and locking surfaces at opposite ends of the locating apertures adapted for mating engagement with V-shaped locking grooves and surfaces in the segment locating and retaining members.

16. An interchangeable and replaceable composite posite radial ends of the tongue portion. 14. An interchangeable and replaceable composite abrasive segment according to claim 11 wherein locat- 0 ing apertures in the tongue portion have:

abrasive segment according to claim 11 wherein the tongue portion further comprises:

guide means at opposite ends of the locating apertures for engaging portions of opposing inner sides abrasive segment according to claim 11 wherein the of the locking groove and aligning the locking grooves in the segment locating and retaining members therewith.

17. An interchangeable and replaceable composite abrasive segment according to claim 16 wherein the guide means comprises:

beveled surfaces at opposite ends of the locating holes in the tongue portion.

l= l l:

Claims

1. A relatively large segmental cut-off grinding wheel comprising: a relatively large, thin reusable drive center rotatable about its axis having a peripheral surface, opposite sides extending to the peripheral surface, at least one narrow segment aligning groove of predetermined axial width extending inwardly from the peripheral surface a predetermined radial depth to a bottom surface extending axially between opposing inner sides of opposed spaced side flange portions of the center, a plurality of axially aligned apertures of predetermined size and shape extending axially through the side flange portions with axes situated and spaced on a first base circle of predetermined radius from the axis; a plurality of interchangeable and replaceable composite abrasive segments mounted around, attached to, and displaceable radially relative to the center, each having a bonded abrasive portion of predetermined axial thickness, a segment base member having an outer radial portion fixed to an inner radial portion of the abrasive portion, a tongue portion, radially displaceable relative to the center, extending radially inwardly from the abrasive portion and slideably into the narrow segment aligning groove, a plurality of segment locating apertures, in the tongue portion of substantially the predetermined size, shape and spacing between their axes as the axially aligned apertures in the opposed spaced side flange portions and displaced radially so their axes lie substantially on a second base circle of greater radius than the first base circle of predetermined radius from the axis of the center; a plurality of axially movable segment locating and retaining members slideably mounted within the axially aligned apertures in the side flange portions of the center and extending axially through the locating apertures in the segment support member radially displaced into engagement therewith and each having a locking groove, including a segment locating surface engaged by the displaced segment support member therein, of predetermined depth between opposing inner side of spaced end portions of the segment locating and retaining member; and resilient means engaging the center for biasing and displacing each of the segment support members radially outward relative to the center into engagement with the segment locating surface in the locking groove and maintaining the abrasive segments in a precise radial position on the center, whereby the segment locating and retaining members are engaged, locked in place, and prevented from shifting axially by engaging portions of the segment support members biased into the locking groove and the abrasive segments may be quickly attached and detached from the center by radially displacing them inwardly against the resilient means sufficiently to shift the axes of the locating aperture from positions on the second base circle into axial alignment with the axes of the apertures in the side flange portions situated on the first base circle, and the segment support member out of the locking groove therein and sufficiently displacing the segment locating and retaining members axially relative to the center.

2. A segmental cut-off grinding wheel according to claim 1 wherein the resilient means comprises: a pair of cantiliver spring members on the tongue portion of the segment support member each having an end portion anchored to a lower portion of the tongue portion; and an elongated deflectable portion extending longitudinally from the anchored end portion, displaced into forceful engagement with the center within the narrow aligning groove sufficiently to exert a force necessary to displace and maintain the segment support member radially outward against the segment locating and retaining members.

3. A segmental cut-off grinding wheel according to claim 2 wherein the cantilever spring members are an integral part of each segment support member comprising: a pair of the narrow elongated deflectable portions extending longitudinally in opposite directions from a central lower anchor portion of the tongue portion along and including the lower inner edge of the tongue portion toward opposite radial ends of the tongue portion and displaced into engagement with the center within the narrow groove; and a pair of elongated slots adjoining the deflectable portions and extending a predetermined depth from the opposite radial ends of the tongue portion.

4. A segmental cut-off grinding wheel according to claim 1 wherein the center has one continuous narrow segment aligning groove extending circumferentially around the center and into which each of the segment support members are slideably mounted, and wherein the plurality of axially aligned apertures are arranged into a plurality of groups equally spaced around the center, each group having an identical number of at least two of the axially aligned apertures with their axes situated and spaced on the first base circle, extending axially through the spaced opposed side flange portions.

5. A segmental cut-off grinding wheel according to claim 1 wherein the center has a plurality of narrow segment aligning grooves of predetermined arcuate length angularly spaced around the center and extending radially inward from the peripheral surface a predetermined radial depth to bottom surfaces extending axially between opposing inner sides of a plurality of angularly spaced sets of spaced opposed side flange portions of the center; a plurality of spacers extending radially between and separating the plurality of narrow segment aligning grooves and sets of the spaced opposed side flange portions; and wherein the plurality of axially aligned apertures are arranged into a plurality of groups equally spaced around the center, each group having an identical number of at least two of the axially aligned apertures, with their axes situated and spaced on the first base circle, extending axially through each set of the plurality of angUlar spaced sets of the spaced opposed side flange portions of the center.

6. A relatively large segmental cut-off grinding wheel according to claim 5 wherein the spacers between the segment aligning grooves are an integral part of the center and have curved side surfaces of predetermined curvature at opposite angularly spaced radial ends of the narrow aligning grooves extending from the bottom surfaces to the peripheral surface of the center and defining the configuration of the narrow segment aligning groove; and wherein the tongue portion of the segment support members have curved radial edges spaced from and corresponding substantially to the curvature of the curved side surfaces; and a configuration corresponding substantially to the configuration of the narrow aligning grooves.

7. A relatively large segmental cut-off grinding wheel according to claim 1 wherein the locating apertures in the tongue portion have substantially straight internal locating surfaces extending between opposite ends and edges thereof at opposite sides of the tongue portion; and wherein the segment locating and retaining member may selectively have generally U-shape rectangular locking grooves and V-shape locking grooves and locating surfaces for selectively engaging the straight internal locating surfaces and the edges of the locating apertures.

9. A relatively large segmental cut-off grinding wheel according to claim 8 wherein the guide means comprises: beveled surfaces in the portion of the tongue portion at opposite ends of the locating apertures in the tongue portion.

11. An interchangeable and replaceable composite abrasive segment adapted to be mounted around, attached to, and displaceable radially relative to a relatively large thin reusable rotatable drive center having an axis, at least one narrow segment aligning groove of predetermined axial width extending inwardly from a peripheral surface a predetermined radial depth to a bottom surface extending axially between opposing inner sides of opposed spaced side flange portions of the center, a plurality of axially movable segment locating and retaining members, each with a segment locking groove and locating surfaces therein between opposing inner sides of spaced end portions thereon slideably mounted within axially aligned apertures in the side flange portions of the center with axes situated and spaced on a first base circle of predetermined radius from the axis and the composite abrasive segment comprising: a bonded abrasive portion of predetermined axial thickness; a segment base member having an outer radial portion fixed to an inner radial portion of the abrasive portion, a tongue portion extending radially inwardly from the abrasive portion adapted to be inserted and slideable into both the segment aligning groove and the locking groove and displaced radially into locking and locating engagement with the locating surface in the segment locating and retaining members in the center, a plurality of segment locating apertures and locating surfaces in the tongue portion of substantially the size, shape and spacing between their axes on the first circle as the axially aligned apertures in the opposed spaced side flange portions and through which the segment locatIng and retaining members pass and engage the locating surfaces in the tongue portion; and resilient means, on the tongue portion, for forcefully engaging the center within the segment aligning groove preloaded by displacing the abrasive segment sufficiently to align the locating and axially aligned apertures and inserting the segment locating and retaining members therein and upon releasing the abrasive segments for biasing and radially displacing the tongue portion outwardly relative to the center into the locking groove to maintain the locating surface of the tongue portion in locating engagement with the locating surface of the segment locating and retaining members which are thereby locked in place against axial movement relative to the center and shift the axes of the locating apertures to positions on a second base circle of greater radius from the axis of the center.

12. An interchangeable and replaceable composite abrasive segment according to claim 11 wherein the resilient means comprises: a pair of cantilever spring members on the tongue portion of the segment support member each having an end portion anchored to a lower portion of the tongue portion; and an elongated deflectable portion extending longitudinally from the anchored end portion displaced into engagement with the center within the narrow aligning groove and deflected sufficiently to exert a force necessary to displace the segment support member radially outward against the segment locating and retaining members.

13. An interchangeable and replaceable composite abrasive segment according to claim 12 wherein the cantilever spring members are an integral part of each segment support member comprising: a pair of narrow elongated deflectable portions extending longitudinally in opposite directions from a central lower anchor portion of the tongue portion along and including the lower inner edge of the tongue portion toward opposite radial ends of the tongue portion and displaced into engagement with the center within the narrow groove; and a pair of elongated slots adjoining the deflectable portion and extending a predetermined depth from the opposite radial ends of the tongue portion.

14. An interchangeable and replaceable composite abrasive segment according to claim 11 wherein locating apertures in the tongue portion have: substantially straight internal locating surfaces extending between ends and edges thereof at opposite sides of the tongue portion for selectively engaging the locating surfaces in both generally U-shape rectangular locking grooves and V-shape locking grooves in the segment locating and retaining members selected for use therewith.

15. An interchangeable and replaceable composite abrasive segment according to claim 11 wherein the tongue portion further comprises: beveled locating and locking surfaces at opposite ends of the locating apertures adapted for mating engagement with V-shaped locking grooves and surfaces in the segment locating and retaining members.

16. An interchangeable and replaceable composite abrasive segment according to claim 11 wherein the tongue portion further comprises: guide means at opposite ends of the locating apertures for engaging portions of opposing inner sides of the locking groove and aligning the locking grooves in the segment locating and retaining members therewith.

17. An interchangeable and replaceable composite abrasive segment according to claim 16 wherein the guide means comprises: beveled surfaces at opposite ends of the locating holes in the tongue portion.