[1]rb- iL x-axented Feb. 1937- 2@072pOSl UNILTED STATES PATENT. @OFFICE 2,072,051 ABRALSI[VE WHEEL ,Edward Van der Pyl, Holden; Man., assigner to Norton Company, Worcester, Mass., a corpora@ tion of Massachusetts Application August 12, 1935, Serial No. 35,881 .6 Claims. (Cl. 51-280) The invention relates to abrasive vheels and a gether in a melting Pat hi the proportions desired and melt them together. I then cast ingotz of the alloy in sand molds. These ingots I then crush by means of crushing robers or the like until the alloy is in powdered form ok the desired mesh size. With the powdered metallic bond of the type indicated I iriix in the neighloorhood of between 25% and 50% by -volume of diamond bo-Et in a grit size of between 80 mesh and 500 mesh, for 10 example. Mesh size of the bort selected will de-@ Pend u Don the abradizig operation that the wheel is to @erform, and my invention has no limitations in this respect, in so much as grinding, pohshing and lapping operations differ vastly among themselves. For the flner polishing or lapping operp-- tions, finer grit size of bort will be used. The mesh size of th-e metallic bond May also var7 betw@en wide limits; I merely note that using loo niesh diamond grit, powdered bond of 200 mesh Is highly practical, but other mesh sizes of the bond may 20 be used even with the given size of diamond grit. The niixing of the grit with the bond way be accomplished manually, for although machine rneth-ods might be used, the bort or diamond dust is so valuable as to dictate care in the mixing to 25 avoid loss of diamond. Setting apart a measured or desired quantity of. mixed bond and bort, IE place it in a mold. This mold may take any form, for although I aiii describing the irivention in conabrasive bodies are to be deemed included. In case the abrasive body Is a wheel, In most cases It will have a central hole for mounting upon an arbor or the Uke @;and accordingly in such cases the Shape of the i@@ld is ananniuus For the ma- 35 terial of the mold I prefer trapite, on account of its many desirable properties, such as, that it may be e6sily destroyed to reltove the-formed wheel; It has an affinity for oxygen thits inhibiting 40 oxidati on of the niaterials of the wheel; it Is reaso nably.inexpensive; it may be easily machined into desired form or shape; it will not melt and will not go to pieces under any temperatures which I contempla;te using. 45 Hav ing placed the desired quan'tity of mixed grsin and bond In thp mold selected, I apply lieat and pressure. Within the limits of my inventioz, the pressure -range is wide, and the heat employed is siich as to cause sintering of the bond at the pressu re employed or under the conditions of intima teuliionachieved. Forexample,Iinaycold Pre6s the bond and -abmsive grain, heating the substa nce thereafter. Itr"uch- bases I raight use a mold other thazi graphite ii),, connection witkl rr 30 structed in accordance with certain features of the ., nection with the manufacture of a wheel, other 30 method of making the same. One object of the invention is to provide a low melting point nietallic bond for diamon&. Another object of th-e inventiori Is to provide a grinding wheel for grinding very hard substap-ces. Another object oi the'- iiivention is to provide a grinding wheel comprlsing very hard grain and c, bond suitable therefor. Another object of the In10 vention is to provide a bond for diamond abrasive from which the diamonds may be recovered at small expense and viithout destrtiction of the diamonds. Another object of the invention is to pro,vide a method of bonding carbonaceous grain a5 which is effective and wbich ma@y be carried out without burning the grain. Other objects wi)l be in part obvious or in Part Pointed out hereinafter. The invention accordingly consists in the features of construction, combinations of elemeats, 20 and arra-agements of parts, and in the several steps end relation and order of each df said steps to one or more of the others thereof, all as will be illustratively described herein, and the scope of the application of which will be indicateci 25 In the following claims. . lia the accompanying &awing, in wlach is shown one Of vatious Possible embodimelits of the mechanical features of this Invention, Mg. I Is a plan view Gf a grinding wheel coninvention, Mg. 2 is a cross sectional view on the line 2-2 of Mg. 1. According to the Preferred method of carry35 ing out myinvention, I prOVide diaixond grit in finely divided or grain form. Diamond grit which, because of its ext-reme hardness and its other qpalities, constitutes probably the best abrasive substance known, exists In a form romniercially '10 known as "bort" which is commerciaby available in sufficient quantities and at SUCH prices thut It may be used for the manufacture of grinding wheels and other abrasive bodies. V@bfle bort Is expensive, nevertheless on account of the great 45 superiority of the diamond for abradant purposes, the wheel formed thereof bas mmny practical uses and advantages. Also, in the preferred embodiment of my Invention, I provide bond in the form of a Dowdered 50 alloy. Although such Powdered bond raight be a mixture of two or more metalue powders, I prefer to proceed as fohows. Selecting two or more metals according to considerations h-ereinafter @et fortli I put them to-
[2]2 2iO72,061 plunger and pressure mechanism, beating the formed or "green!' wheel on a "bat". The union of the metamc grain after it has been pressed Is. such that it may be formed Into a practicauy Integral n=w @which WIR tightly hold the abrasive bodies ty heat treating at a temperature which does not comp@etely, melt to a liquid state but,'@ ranters.. The separate pressing and, heating of the ba(lies has the advantage thot a simpler aplo paratus and a cheaper inethod may be employed. However, In certain cases the heat and pressure may be ap@lied simultaneoiwy. - Considering now the bond employed aceording to my invention,.T preferably use an alloy of cop15 per. With the copper I alloy another metal which Produces an alloy harder'and more brittle than coPPer. I desire the bond to hold- the diamonds flrml.v, to be tough enoughso that the diamonds w)ll not rip out, and nevertheless at a certain 20 Pressure and resistance to go to pieces rather than glaze. It is desirable that the bond showd crumble off In little bits or fine fragments so as to.expose new cutting edges of the diamond from time to time, and an alloy or metal which can .25 be crushed to powdered form may have the desired characteristics. I give below examples of specifte alloys which I may use. E=2nple 1 @l forin an alloy of 68 % copper and 32% tin. This alloy is a bronze havin brittle 9 30 characteristics. Although the exact pr@oportions indicated need not be employed, nevertheless I prefer to use something around these Proportions as this is a fairly critical range and substantially different proi@ortions of copper and tin do not 3r) have the saml, characteristics. TIUs alloy melts at 7501 C. and enables me to sinter it at a temPerature at which there is very little danger of o3ddizing the diamonds. I ExamPle 2,1 make an alloy of copper and 40, nickel, 35-50% of copper and 65-@50% of nickel. This also has brittle characteries ilnd is tough. It melts at around 1200, C., but I may use the Precautions her6inafter referred to to prevent oxidation of the diamond or the bond. 45 Example 3,I make an &Boy comprwng approximately 85% copper with 15% alurainiim. This melts at around 10500 C. and has brittle chiiracteristies but is fairly tough. _ ' ExamPle 4,--I make an alloy of copper and r)O mangan6se, 65% or moee of copper and 35-20% of manganese. This melts at 9000 C. and has the' properties of toughness and brittleness desired. Example 5-I use nearly purd copper but mix in with it a very smar proportion, from a trace 55 to, 1% or 2%, of beryllium (glucinium). Copper m6lts at 10651 C. or thereabouts. it is advantageous to take certain, precautions against burning of the diamonds@in the case of the alloys which sinter at the higher tem60 'Peratures, for example above 900, C. The use of a graphite mold or container durlng the heatlng operation is such a precaution. However. even when a graphite mold is used, and more especially so when it is not, it wiU be well to heat the body In 65 a non-oxidizing atmosphere, such as nitrogen or hydrogen. I have also found that a small amount of aluminum, silicon or magnesium may be Introduced into the bond, preferably as separate dis70 tinct metaric particles, that is not In an alloy state,- which wfli inhibit oxidation of diamond and bond because such mbtals have a grert sffinlty for oxygen. In many cases I desire to make the bond as la brittle as possible for the specific alloy used and brittleness b enhanced by quenching the abroaive bodv when still hot from the heat treatment. One marked adv'antage of a wheel constructed according to the Invention lies in the fact that, when produced In annular form, it may be readily 5 imited to a central disk. I)Iamond grinding wheels are, under present market conditions, expensive, whatever the bond used, owing simply to the high price of bort, and accordingly it Is highly desirable to waste as little of the diamond io as is possible. In the case of any grinding wheel which is thin relative to its diameter, the central part will generally not be used for abrading. Apcordingly, In the case of diamond wheels It Is preferred to form the central part in the form of is a non-grinding disk or annulus. V4We a small internal grinding wheel, having a length on the, order of half its diameter, may comprise 100% grinding substance and be attached by mounting directly upon a spindle, in the case of a cutting- 20 off wheel or a large sized wheel for the grinding:of the cemented tuii9sten carbides and other hard substances, it Is generally found economical to secure what amounts to an annular band of diamond grinding material to a central disk having 25 a hole therein. Therefore, a distinct problem hag arisen in -attaebing the inside of the annular band of grinding subrtance to the periphery of the central supporting disk. If the unibn between the parts is weak, fracture will result and this 30 destroys the grinding wheel which may have a market value In the neighborhood Df from $50 to $200. According to the present Invention, with diamc.&,i bonded with metable bond as disclosed In 35 the foregoing description, I may provide a thill aluminum. disk, or a disk of any other metal, and form my grinding substance in the shape of an annular band whose inside diameter is the same as the outside diameter of the disk. I may then 40 unite the disk to the grinding band by brazing, soldering, preferably with silver solder, or by any other metallurgical operatlon for integrany uniting metsas, such as welding or the like, and the result Is an integral structure of central SUPPOrt- 45 Ing metallic disk having an annular band of grinding substance on -its periphery lnclucupg diamond gmin bonded in a metal bond. Pbr cutting-off wheels an& the like, the central supporting disk should be no; thicker than the annular 50 band of grinding material. Referring now to the drawing, I provide a central disk I 0 which may be mad6 of any suitable metal, such as aluminum. According to any of the methods hereinbefore disclosed I forin an abrasive annulus I I whose 55 Inside diameter is the same as the outside diameter of the disk I 0. I then attach together the disk IO and the annulus II by means of silver solder 12 or otherwise in accordance with the foregoing. Desirably the disk .10 has a central 00 hole 13. Although I have noted throughout diamond as the abrasive grit,' certain advantages Inhere in the combination of the bond specifled with boron carbide grit. Boron carbide is an expensive abra- 65 sive grit, although not,as expensive as diamond bort. Futhermore, boron carbide as well as diamond should not be exposed to high temperatures, or if it Is only for a short time and with suitable precautions sue . h as Indicated, In order to avoid 70 oxidatioh and other chemical changes. The bonds described herein are aU of them reasonably low melting point bonds, and they fuse or sinter at a somewhat low temperature when under pressure or when the particles are In intimate con-
[3]2,072,051 tact as described, and accordingly these bonds are very suitable for the bonding of diamond and other carbonaceous substances such as boron carbide. The bonds of the Invention are more in the nature of a matrix than the common vitrified bonds, and they are harder and tougher than the artificial resinous bonds, and have properties different from t hose of a rubber bond, and the properties of the bonds of this invention are highly 10 desirable in combination with grain of extrenie hardness such as diamond and boro I n carbide, on Moh's scale extension 15 and 14 respectively. It will thus be seen that there has been provided by this invention a method and an article of 15 manufacture or composition of matter in which the various objects hereinabove set forth together' with many thoroughly pra@tical advautages are successfully achieved. As various possible em20 bodinients might be made of the mechaniw features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of 'the invention, it is to be understood that all matter hereinbefore set forth is to be Interpreted as luustrative and not In a Bmiting sense. I
