US2383519A - Manufacture of abrasive articles - Google Patents

Description

Aug. 28,1'945. D. B. ISHARPE 2,383519 INVE DONALD Jxmepe BY I Patented Aug. 28, 1945 MANUFACTURE OF ABRASIVE ARTICLES Donald B. Sharpe, North Tonawanda, N. Y. as-

signor to The Carborundum Company, Nlagara Falls, N. Y. a corporatlon o! Delaware Appllcatlon June 27, 1944, Serial N0. 542,320

s Claims (C1. 51-297) 'I'hls lnverxtion relates to the manufacture cf abresive articles. More particularly, lt relates to the marmfacture of bonded reslllent abrasive articlesof a cyllndrlcal shape, mounted or unmoun'ted. h aving a. mild or soft abrading action and Iormed 013 a. composite of felted flbrous sheets having abraslve grains and usually an adhesive binder therefor, included internally of the fibrous sheets. The inventlon especially pertains to improved methods of ma.king such abrasive artlcles from plurality of adheslvely combined flexible flbrous, abrasive-containing sheets or web material, und especially articles of relatively smal1 s1ze, whereby large numbers of the articles can be more facilelyand quickly formed and in which the res111tant products are characterlzed by a more uniform density lind hardness grade throughout, a. treedom Kram defects, und a mild or soft abrasive actiou whlch combines an efiective cuttin8 rate with an eflicient and 'satisfactory polishing actlon.

There ha.s alwaYs'been a. need for abraslve articles cf the bondea type which' would combine an efl'ectlve cutting action with satisfactory finishing or polishing whereby a reasonable amount 01' materia.l would be removed from the work bein8 abraded and at the same time thearticle would be 1eft with a desirajble surface finish or. .po11sh. F01 a. lang tlme abrasive articles provided for such dual purposes failed to be completely satisfiwtonr in accomplishing both goals and have been Iound to be defectlve in one respect or another. Among the reasons for their unsatisfactoriness have been the failure to conibine an appreciable degree 01 cuttlng abillty with a resllience or "softness o! cutting acti on n0n-homogeneity o: the abrasive artlc1e, 1ack cf permanency cf the abrasive coutent (l. e. fallure 015 the abra5ive wheel struc ture to retain the abinsive particles within the abrad- Ing body) non-uniformity ot abrasive action, inflexibility, etc. Provision of satisfactory propertles in one respect has usually been at a sacrifice 01 one or more 01 the other characterlstics deshable in such products.

Ordinary bonded abrasive artlcles of me prior art consisting ot abrasive grains arm a blnder therel'or in which var1ous flbers have kgeen incor- D0rted for reinforcing means or for'other purposes, an account of their harsh, hard cuttlng behavior, have never been found suitable for the purposes herein sei; forth. They du not; provide an actlon equivalent. or comparable to the comblned sott" cutting und. polishlng actlon of the present artlcles.

Recently, abrasiive articles havlng a comblned cuttlng am! polishing fl ctlon have been made from a. plurality 01 felted flbrous abrasive-containing sheets superlmposed one on the other and adheslvely or otherwise secuxed in position for grinding and polishing use. Such artlcles and methods o1 makingthexn have been set forth and fully described in copending application Serial N0. 408,936, filed August 30, 1941, which has issued as Patent 2355667 August 15, 1944. According to the procedure described therein, abrasive wheels and shapes are iormed by cutting pieces of the abraslve-containlng fibrous sheet materlal of the size und shape of the desired amc1e from a roll cf the abrasive web'mate'rial und assembling the pleces directly to form the desired aiticle. While the resultant articles have sho wn a resilient cutting action of the deslred type the methods cf maklng them have been fraught with numerous procedural difliculties when applied to a carrying out 01 the inventl0n an a large or commercial anale. The making of abrasive wheels and bodies 01 relatively small size having a. cylindrical shape, that is an abrasive body in which the thickness tramsversely of the cyli ndrical 01' peripheral grindin: surface is in excess, und usually as much as twice er more, of the dlame'ter cf the cylindrical shape. has posed numerous problems. The difficulties 01 handling large numbers of small indiv1dua.l pieces for making such small aylindricai have shown a. resllient cutting action of the deslred type they have retained a. defect; of the canbers oi abrasive articles can be fabrlcated efficiently anal efiectiyely with an ease and simpllcity of manufacture not heretofore attained. By my impr oved process the need fr molds is eliminated and the material requires but a single pressing operation. Furthermore, the peripberal cutting faces of the resulting cyllndrical bodles as herein made have animproved uniformity and are retentive of all the soft cutting an d polishins characteristics so d'esirable in such articles. 'I'he herein-described methods, by reason of the 1x1- creased rate 01 production made possible and the improved unlformity' of products obtained thereby, result in economlc savings es we1l es the' cc'rual of other advantages, all of which will become apparent as the descriptlon proceeds.

In accordance with the present lnverltlon,

sheets of felted fibrous abrasive-conteixflng web material are initially formed in'to a relatively large slab of compacted and matured materialwhich is cut into rectangular sections each of whlch has a thickness and width equal to or slightly greater than the diameter of the cyllndrical shape desired, and the rectangular sections are finally dressed 01' trimmecl, as on a. lathe, so a cylindrica! shape and, ifnecessary, cut to"length. In

forming cylindrical wheels pi*ovided with a cen-' tral arbor hole, the arbor hole may be formed in each rectangular segmei1t at' the time the entire slab ls formed by the insertion of metal or similar rigid rods midwayand es part cf the assembly 01 sl1eet material in the manner described in detail later. Mounted cylindriwl shapes are sim'llarly formed in which the cylindrical body is provided with a mounting spindle, as will also be described.

' and similar substances. 'I'he size of the abrasive imposed upon the preceding membranes until a web cf loosely felted flbrous material of the deslred thickness is built up on the travellng support. A number of abrasive grain hoppers are also disposed between the carding assemblies und above the tra.veling conveyor. Abrasive grain is fed from the hoppers onto the fibrous membranes at varlous stages in the bullding up of the final web, sothat, a.s a result, the abrasive material is applied between the lndividual membranes making up the web and so is internally distributed throughout the fibrous web or sheet. A suitable adhesive binder ls then lncorporated within the fibrdus-abrasive web and the web is consolidated to a desired density and passed to a. curlng zone, where the--adhesive is matured or set. The included-abrasive web is then wound into rolls for use es a source material for the manufacture of the prbdudts herein described.

In practicing the invention, any of the abrasive materials in comm0n use may be employed. such es silicon carbid e, diamonds. boron carbide, tused aluminum oxide, fiint, corundum, emery, rouge particlesmay vary from the finest; pdlishlng or bufllng powders to the eoarser grlt slzes usedln grlriding. Other-miathods o1 incorporatih3 abraslve material inte rnally of the flbrous sheet material dur- 1ng its manufa.cture may be employed. For exemple, the abrasive blnder andthe mixture applied to the uncompacted web by the 'usual adheslve-applying -rolls. 'Ihis method has' been In order to better understand the natura of the invention, reference is made 120 the accompanying drawing in which: v

Figure 1 is a perspective view of a compacted ahd matureci slab, composed of a number ofsuperlmposed sheets of felted fibrous abrasivecontalning webmaterial; the slab depicted is marked to show the manner in Which a number 0f abrasive cylinders can be obtained therefrom;

Figure 2 is a perspective view of a slab similar in composition to the sla.b shown in Figure 1 but which 1's adapted to the making of cylindrical abra sive wheels having centrally located arbor' holes formed by the pr0vision in the slab of a number of rigid metal rods suitably positioned therein;

.Figure 3 is a perspective viewof an abra.sive

foundto be particularly satisfactory for the inclusion of'the finer abrasive materlals of the slze employed in bufllng and polishing operatlbns.

- Another method is to project the abrasive material into the web or sheet' after lt has' been built up to the de'sired thickness and lmmediately' 'prlor to consolidating the web. 'I'he projectlon of graln is sitably carried Gut by means of a blast o1 air or gas against one or both surfaces of the fibrous web, the air stream being laden wl'th the abrasive material to be included i'nternally-of. the web. The' other steps in the formation and consolidation of the web are carx -ried out in a manner similar to that used in the cylinder represencative of those to be obtained from a slab such as that shown inFigure 1;

Figure 4 is a perspective view of an abrasive wheel of the type obtained from -t;he slab shown in Figure 2; anal Figure 5 is a perspective view 015 a. cylindrical mounted abrasive point such as is madefrom a sleb of the type shown in Figure 1.

'1ne abrasive-includeci fibrous web material usecl in making the products of the present invention can be manufactured in several ways. The abrasive and adhesive content 015 the fibxous material is incorporatedand distributed throughout the fibrous web at the time of its manuiacture and constitutes an integral part thereof. A very satisfactory method of maklng in'cluded abrasive sheet materlal of the herein required type is that sei: forth and fully described in U. S. Patents Nos. 2284,715 and 2,284,716. Briefiythe felted fibrous web is formed by feeding a plurality aerodynamic weaving" v (Ehe Web. F01 a more of thin carded fibrous membranes from a number previ0us -procedures.

- Felted fibrouswebs having abrasive material lncluded within the web and which are suitable for use in the fabrication 015 the herein-described products can alsobe made by a modification o! the above processes in which the individual fibers are interwoven und interlocked by a geniale an or gaseous agitation of the thln carded membranes during their deposition. 'I'his process ls termed and is used to promote -the strength and eliminate any laminations from complete descrlption o! such a process and product, reference is made to U. S. Patents Nos; 2;284738 and 2284,739 in which further details a.re also given of the above procedures forincluding abrasive materials wlthin the fibrous structures.

Abrasive-included sheet material- 01 the hereinrequired type can also be mde by certain feltlng proc edures employrlng the various types cf paperstock fibetg and including abrasive therein at the time of making the sheet materials. One satisfactory method of making the abrasive-included s heet materlal by wet 'feltingprocedure is that set forth and fully described in cbpending application Serial N0(461139, filed October 7, 1942.

Briefiy, the felte'd fibrous paper-stock material having abrgsive grain incorporated internally thereof is made by first forming a, liquid, usual1y equeous, 'suspension of flbrous material, the ber content of the suspension being very 10W and in the ntighborhood =of 0.5 to 5% of the suspension, collecting' the fibrous suspension on.a suitable suppoxt, introducingabrasive grains with or without an adhesive binder into the fibrous web while it is in a highly aqueous, or fluid, conditi on' extractihg the wa.ter er other liquid medium from the weblzmd further drying and compacting the web to the dcesired density. Optionally, the abrasive grains can be given a preliminary eoating of a. suitable adhesiye, which is preferably solubleor softenable in -the liquid suspending mediumor a component the1eof, -to assist in holding the fibrous. abrasive-containing web in exampacted form after it has been compressed. The process can be carried 'out in a number of ways.

In one such modification the fibrous suspenslon oi paper stock'is deposited upon a. foraminous support in one step and the abrasive grain is deposited in several increments while the web is still in a highly aqueous or fiuid condition. Tht portion 015 abrgsive applied first penetrates deepest into the web structure, and theabrasive 01 eaeh succeeding deposition penetrates the web to a lessep degree by reason of the continually de'- creasing amount of water present and the consequent thickening of the fibrous body. The distribution of abrasive within the web can th\1s be controlled by Variation cf the amounts anal places of deposition dring the dewatering of, the web so as to obtain any desired efiect.

In a modified form of the process a fiuidfibrous suspension is collected upon a pluralityofmvolv 'ing foraminous supports, such as cylinders, which a;re partially immersed in the fibrous suspension. The thin fibrou membraneg collected uponthe foraniinous supports are theh suc ces:

sively transferred 130 a common earrier, usually a moving endless fe1t blanket or belt, in superimposed relationship 120 form a fibrous web structure. Abrasive grain is incorporated into the fibrous web structure by deposition or projectlon between ai.nd into the various individual Inem branes as they are deposited on the carrier support. This method ha.s the advantage that since the fibrous suspensions can be varied, the composition or structure of varlous portions of the web ean be varied if desired. Aclhesive binders can be incorporated in the fibrous web, rega.rclless df the procedure used, at various stages in the process, such as by inclusion in the fibrous suspension, introduction during dewatering o1 the web, with the abrasive grains as a coating thereon, o;- after the web has been substantially dewatered and prior 120 the final compacting and thin fibrous membrane is conveyed overone er more suetion boxes to remove a portion cf the water and passed between a pair of pressure rolls. As the fibrous material passes between i;he pressure rolle it is transferred 110 the upper pressure roll upon which lt is wound in a series of successive layers until the desired thickness of fibrous material is obtained, whereupon the material is removed by hand or by a suitable knife or doetor b1ade. Abrasive grain is fed onto the flbrous sheet previous to its passage between the pressure rol.sand is thereby incorporatzd within the fibrous strueture.

Another satisfactory -methoci of making included abrasive paper-stock web materialiS that set forth and fully described in copending application Seriell N0. 461,140;fi1ed October 7, 1942.

In accordance with the process therein Set forth, fibrous paper stock abrasive she'et material is made from an aqueous suspension 0f arouncl 3% flber content in which the bers are distributed in the suspension as -substantially individua lly separated bers. This fibrous'suspension is agitated, beaten or otherwise mech:micaliy treated, with suflicient vigorio render the fibers partially.gelatineus abra'sive grain be ing incorporated in the suspension to the desird extent.

A sufficient amount of abrasive grain is 'added to.

provide an abrasive grairi content of over 40%,

.and preferably (SO-770% or more' by weight, 015

the final product after the weiter has been extracted. The agitation of the fibrous suspenslon previous -to and/er during the addition of abrasive grain is veryimportant in preparing a liquid in which the abrasive particles will rema.in uniformly in susp'en'sien. The stability of suspen Si0l1 is believed- 159 be due, als least i'11' part, t-o the adherence oi"phe abrasi ve particleS;t0 the partiallygelatinized'fibers. The amo1irit of agitation or beating.of-th fibrous suspension'necessary to provide z.psuitable stable mixt1 1re cf a.brasive and fiber"of the proper consistency depends upon the'=size of the abrasive part'icles. For example. a; yery slighb agitation' serVes the purpose when the flnest abrasive polishin'gpow ders are usedwhexyeas with the use of or g1'it abrasive grains, it'is desirable to subject the suspension to a much loner and/or more vigorous agitation. Suspension of the abrasive particles may be-assisted by in corlaqrating an adhesive in the flu'id mass, either inthe form of a preliminary coating ofithe abrasive particles o1 by the addition e f the adhesive to tlie'liq uid. In either case, the 'f adlxesive should pref erably be soluble in theliquidfimedium of the suspension 0r at least softenab le or solublein a comp'onent thereof. 4

After a fiber-abrasive suspensiqn of 'suitable consisteney has been prepared as above outlined, it is flowed or otherwise deposited on-a suitable Ioraminous support in the form of a. continuous, highly aqueoug layer fromwhich the Wafcer or other liquid suspending medii1m is extracted, and the resulting film is further dried and compacted to the desired density. These operatlons can be performed by floWing the suspension onto a moving endless wire screen 0; by collecting a plural- 1ty of thin membranes ontocylindey molds and transferring them to a suitable fel1; blanket in superimposed relation to form a web'f'the desired thickness Whi1e it is usually desiralble to proceed in the described manner of fqrmin Centinuo1is fibrous webs by this particular method, the process can be practiced in modified form by using the sam e thin suspension of fibers an'd abrasive to form individual abrasive-ineluded sheets by a seiies of discontinuous steps. Adhesive binders can be incorporated in the fibrous web regardless o1 the procedure used;at various st'age in the process such as by inclusion in the fibrous suspension, introduction during dewatering of the web, a5 a coating on the abrasivg grains, 01 alter the web has been substantially dewatereci and prlor the final compacting anti drying of the web.

the material.

Modifying agents such as waterprooflng compounds, antl-friction agents, flexlbillzers, plasticizers and other flllers may be incorporated in the web als the time o1- making lrrespectiVe o! the particular procedure followed, in order to render the web resistent to water or lmpact other speclfic desirable properties to all or certain cantrolled portions of the Web.

Abrasive-included felted fibrous web materlal such as tha1; made by any one o1 the aforementioned methods is used as a. source or raw materlal'tor the making o1 abraslve articles in accordance with the present lnvention. As a speciflc example of the manner in which the present process has been ca.rried out and abrasive artlcles made in accordance wlth the teachlngs o1 the present lnventlon, the following procedure is glven.

A flexible, felted fibrous sheet materlal made in accordance wlth the teachings o1 U. S. Patents Nos. 2284738 und 2,284,739, and containlng approxlmately 75% 015 fused alumina particles cf 80 mesh grlt size, 15% cotton bers and10%natural rubber derived fromlatex ls sized witha 20% aqueous solution o1 casein glue (such as "Casco glue marketed and Sld by Casein.Corporatlon 01 Amerlca) to provide about 10% casein by weight based on the fibrous sheet materlal.

Referrlng further to the drawing as a means of lllustrating more clearly the manner in which the present process ls ca1ried out, the roll of adheslvely-sized abraslve-lncluded fibrous web materlal is cut lnto the form 01 indivldual she ets o1 In the pa rticular 1orm shown in Figure 1 a number of square sheets li, measur'ing /2" on a side, are assexnbled in superlmposed relation, pressed between the platens of a hot press and subjected to a pressure.of approxlmately 5000 pounds per square inch end a temberature of 260 F. for 30 minutes for a 1" thick slab.- A sufllcient number o1 the lndiviclual sheets 8 are used to obtaln a. slab 1 which, when compressed, has a, thickness through the sheet materlal at least equal to and usually sllghtly greater than the diameter o f the cylindrical abrasive body to be formecl therefrom. The slabs are then usually given an oven eure as by heating for hours at 260 F.

The sla.b 1s then cut along the parallel llnes 8 into a number 01 .rectangular shapecl segments 9 of square cross-section, the width across the segments being substantially the same as the thicknass through the segments. Each 01 these rectangular Segments 9 is cent;ered 011 a lathe and trimmed anal dressed to a. cylindrical shape as shown by the dotted outline I 0 of Figure l. If the the cyllndrlcal abrasive artlcle to be Iormed, the rectangular pleces can be cut to the proper length before or after trlmming to shape. The slab illustrated, if given a thickness of 1%", can be cut into four rectangular pieces 5 /2" long und of approxlmately 1% square cross-sectlon, each of which can be trimmed in a lathe to provlde an abrasive cyllnder of thelsame length, or shorter i! deslred, a.nd having a. dlsmeter of 1 A. It is deslred 150 hold the thickness and wldth 01 the rectangular pleces es close as possible to the deslred dla.meter of the cyllndrical grindlng shape to be formed in order to avoid an excessive amount o1 trlmming.

Cylindrical abraslve wheels havlng a centrally located arbor hole for mountlng can also be made by modifylng the procedure glven above for the making of solld cylindrlcal articles. A slab tor forming an arbored abrasive wheel 01 cyllndrlcn.l shape ls shown in Flgure 2. In formlng such a slab, after assembling one-half the number cf individual sheets 6 of abraslve web material, a number of small metal rods II are equally positioned parallel to one anothter end spaced so as to be located centra.lly o1 the ends 01 the rectangular segments 9 to be cut; from the slab and proparallel lines slab of the type trudingv from bo'th s1des 01 the sheet materlal. These metal rods are usually wrapped in pa.per or given a. coating of other dlslntegrable materlal to facllitate their removal after the surroundlng sheet materlal htl been compacted. Notched end templets or simllarmeans can be used to maintain the rods in correct allgnment. After carefully positlonlng. the metal rods the remainder 015 the sheets is placed over the rode und the entire assembly subjected to heat und pressure to consolidate the sheet materlal into slab form anal sei; the adhe5l\e bindet, Iollowing which the slabs are usually given an oven eure a.s descrlbed above. The metal rods then are removed to provide a number of holes I2 suitably located to serve, as mountlng arbors in the flnally 1'ormed abrasive wheels. The slab is then cut along the 8 to provlde a. number 01 rectangular pieces of square cross-sectlon, euch havlng an arbor hole I2 centrally located with respect to the cross-section und runnlng lengthwlse 01 th plece. These pleces are then trlmmed to cyllndrlcal shape und cut to length if necessary the sflme as ls done in formlng the cylindrlcal abraslv stlcks.

Mountel artlcles of cyllndrlcal shape can also be made by the present process, in which case a shown in Flgure 1 is formed und the same procedure ls followed as that for making a solld' cylindrlcal grinding stlck except thal; Just prlor to trimming the rectangular plece to cyllndrical shape a hole centrally located of the end cross-section of the piece ls drilled in from one end cf the piece to the requlred depth and the desired rnountlng splndle M insertedand adhesively secured thereln by'means 01 a. sultable cement. Although a cold-setting type cement can be used.

a heat-hardenable cement is preferred in which length of the slab is grea.ter than the length o! case the artlcle is given an over: eure. Asatlsfactory heat-hardenable cement can be made by mlx- 111g a thermo-settlng liquid phenollc condensatlon product with a suitable flller such as powdered quartz to provide a materlal 01 the deslred couslstency for use.

Figures 3, 4, am! 5 lllu5trs.te the type of abraslve artlcles obtained by practlclng the present :lnvention.

Figure 3 shows a solld cylinclrlcal abrasive stlck I5 f0rrned from a large slab in accordance wlth the procedure described abova and composed 01 portions of a plurality of abraslve-included felted fibrous sheets 6 which have been adheslvely comblned and compacted. It is to be observed that the edges I6 of the sheet material extend transversely of the cylindrlcal grindlng surface to provlde a hlgh degree of unlformlty in cutting action over the entire grinding area. The advantages of such a disposition of the sheet; material to the grindlng edge are obvious. Fbr example, when so presented to the work being surfaced, there is considerably lass tendency for the work to be striated than ls the case when the sheeted material ls placed otherwise wlth respect to the grlnding surface.

Figure 4 shows a cyllndrlcal abraslve wheel l'l of similar constructlon but provided wlth an arbor hole I2. Flgure 5 shows a mounted cyllndrlcal abraslve tool I8 mounted on a splndle II. It can face feet per mlnute.

acter 01 the adhesive bindet employed in making the abraslve-containing, fibrous sheet materlal,

. and particularly by the choice of auxiliary or sup--.

plemental adheslve substance which is admixed with the sheet material as a size' thereto. It is desirable that the 'adhesives selected for making the aforesaid articles do not smear during grinding operations. This ls especially true in polishln wheels and devices where smearing of the bond tends to produce a hot cuttlng or buniing action whlch ls ruinus to the flnlsh.being mocluced.

Among' those substances which can be satlsfam torlly used as bonding materials herein in additlon to the speclfic adhesive sizing composltion Set forth above, ancl which are non-smearine, are included glue adheslves, particularly when trea'ted wlth plasticizing agents such as ethylene glycol, sorbitol, glycerine and the like. The plasticizer may amount to es much es 40% by wzelght of the total adhesive blnder. Other non-smearlng adhesives which can be used are caseln glues, natural or synthetlc rubber latices, urea resins. phenolaldehyde resins and other natural or synthetic resins, ormlxtures 013 two or more of such adheslves.

The hereln-descrlbed lnvention ofiers numerous improvements sind advantages over the prior art. It provldes a practical method of fabricating small sized abraslve articles of the mounted or unmounted type such as grincllng and polishing wheels, abrasive stlcks, mounted points and the like, having a soft or resilient combined cutting and polishing action.

The articles of the present invention haVe a relatively high rate of stock remo'val from the material being ground and at the same time produce a surface flnish equal eo that obtalned by an urdinary bonded ablaslve article embodying abraslve partlcles several grlt sizes smaller. Abraslve products made as herein described cut both efiiuiently and effectively, wlth an accompanying polisl.tng action, and are capable cf hlgh operating speeds without chattering, operating smoothly to remove hurrs anal produce very high finishes on metal castngs when operated at 6000 to 9500 sur- It.ls theorized that the "soft" cutting action of such abraslve articles is the result of the abrasive gralns being cushionecl by the surroundlng felted bers and binder so as to prevent gouging ancl scrat-ching and to provide the abraslve grains with a yleldlng backgrouncl by which they are caused to maintain individually more effective contact with the work and at the same time absorb and take up inequallties ofsurface so as not to scratch or mar the surface belng finished.

Although I have set forth, in the specific ex ample certain specific condit1ons, lt will be understood that my invention is not lim'1ted to the conditlons there described. Generally speaking,

1 have found lt to be desirable to molcl the slabs under pressures cf the order of 1000-2000 pounds per square inch. The, length of time that the slab is subjected to heat and pressure is determined to some extent by the size and thickness of the slab belng molded but is usually in the detail, the scope cf the invention is not 1:0 be can- -fined othei than by the appended claims.

I claim: y

1. The method of makine an abrasive article having a cylindrical shaped, bonded abrasive body from a plurality of superlmposed sheets of felted fibrous abrasive-containing web material which comprises assembline a plurality of sheets of felted fibrous, abrasive-containing web materlal in superimposed relation, subjecting the assembly of sald web material to pressure to compact it lnto a. 'slab hav1ng a thickness at least equal to.the diameter of the cylindrical shaped body to be macle, cutting a strip from said slab, said strip havlng a wldth at least equal to the diameter :ot the cylindrical shaped body to be made, and

trimming the resulting strip to llndrical Shape.

2. The method of making an abrasive article haVing a. cylindrical shaped bonded abrasive bocly the deslrecl cyfrom a plurallty of superimposed shets of felted Tibrous abrasive-containing web material whlch comprises assembllng a plurality of sheets of felted fibrous abraslve-contalning web material in superimposed relation, subjecting the assembly of seid Web material to'heat and pressure tocompac t it into a slab having a thickness at least equa'l to the diameter of the cylindrlcal shaped body to be made, cutting a strlp from said slab, said 'strip having a width a1; least equal to the diameter of the cylindrical shaped body to be ?nacle and turning the resulting strip tq the desirecl cylindri'cal-shape.

3. The method of making an abrasive article having a cyllndr'ical shapea bonded abraslve bocly from a plurality of superlmposed sl;eets of felted flbrous abrasive-containlng web material which comprises assembling a plurality of sheets of felted fibrous abrasive-containing web material in superlmposed relatlon, subjecting the assembly of sald web materlal to pressure to compact lt into a slab having a thickness a1; least equal to the diameter of the cylindricalshaped body to be made, cutting a strip from said slab, said strip having a width-at least equal to the diameter of the cylindrlcal shaped bod.v to be made, and trimming the resulting strip tothe desired cylindrica1 shape and cutting the cylindrical shape to the required length.

4. The method of making a bonded abrasive wheel having an axial length als least as great as the diameter of said wheel which comprlses assembling a plurality (f sheets cf felted fibrous abras'1ve-containing web material in superimposed relation, pl3clng smooth cylindrical rods withln the said assembly of sheet material miclway from v made, said rods having a diameter substantially elual tc the diameter of the arbor hole of the abrasive wheel being made.subjecting the sald assembly to pressure to compact it intoja, slab havlng a thickness-at least equal to the diameter of the abraslve wheel being made, removing the seid rds from the compacted slab, cutting the said slab into rectanlllar strips along lines parallel t0 anti equidistant fro m the h0les formed by the said rods and trlmming the resultlng rectangular strlps to a cyllndrlcal shape.

5. 'I'he method of maklng a mounted abraslve article comprising a mountin spindle und a bonded abrasive body 01' cylindrlcal shape which comprises assembling a. plurality of sheets 01 felted fibrous abraslve-containlng web material in superlmposed relatlon, subjecting the assembly of said web material to pressure to comp&ct lt into a slab having a. thlckness et least equal to the diameter of the eyllndricalshaped body to be made, cutting a rectan8ular strip from seid slab, said strip havlng a. width at least equal bo the diameter of the cyllndrlcal shaped body to be made, reducing the length of the rectangular shape to the length of the cyllndrical body t be made, borlng a hole in the center ofone end of the resulting rectangular piece, lnserting and adhesively securing a mounted splndle therein, and trlmming the mounted rectangular plece to a. cylindrlcal shape.

6. 'Ihe method of making a bonded abraslve wheel having an axial length at least as great as the dlameter of said wheel which comprlses assembling a plurality of sheets of felted fibrous abrasive-containing web material in superimposed relation, encasing a number of rigid rods individually in pper sheaths to facilltace the extraction from the surrounding compacted mass, placing said encased cyli.ndrical rods within the sald assembly of sheet material midway from top to bottom 01 the assembly of sheet material and posltloned p'arallel to one another and spaced at a distance from one another sllghtly greater than the diameter of the abrasive wheel to be so made said rods having adiameter substant'iafly equal to the diameter of the arbor hole of.the-

abrasive wheel belng made, subjectlng the seid assembly to heat and pressure to compact it into a slab having a thlckness als least equal t0 the di.meter of the ab'raslve wheel beim; inade, removing the said rods from the compacted slab, cuttins the seid slab into rectangular strlps along lines parallel to and equidistant from the holes formed by the seid rods, and trimming the resultlng rectangular strips to a cylindn'cal shape.

7. The method of maklng a bond d abraslve wheel having an axial length at least as great as the diameter of seid wheel which comprlses assembling a plurality of sheets of felfed fibrous abrasive-containing web material in supeirimposed relation encasing a number 015 rigid rods individually within athin fllm of materlal so that said rods can be easily removed from the surrounding compacted mass, placing said rods within the seid assembly oi sheet material midway from t;op to bottom ollthe assembly of sheel; material und positioned parallel (So one another, and spaced at a. distdnce from one another slightlygreater t.han the dlameter of the abraslve wheel to be so made, saicl rods having a diameter substantially equal to the diameter of the arbor hole ot the abrasive wheel being made, subjecting the sald assembly bo heat and pressure to compact it 1nto a slab havlng a thickness ab least equal to the diameter cf the abrasive wheel being made, removing the seid rods from the compacted slab, cutting the sa.ld slab into rectangular strips along lines parallel to and equidistant fr0m the holes formed by the said rods, and trimming the resulting rectangularstrips to a cyl indrical shape.

8. An abrasive article ofmanufacture comprising a cylindrical abraslve body comprising a plurality of a.dhesively combined sheets of superimposed felted fibrous abrasive-containing web materlal in compacted condition, the edges of 'said sheets lying-transversely of the cylindrical cutting surface of said abrasive body and substantially parallel to the longitudinal axis of seid cyllndrlcal body.

DONALD B. SHARPE.

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