US2258774A - Manufacture of abrasive products - Google Patents

Description

Patented Oct. 14,1941

'UNlTED STATES" PAT ENT oFnc MANUFACTURE OF massive raonnc'rs Joseph- N. Kuzmick, Passaic, N. 3., assignor to Raybestos-Manhattan, Inc., Passaic, N. J., a corporation of New Jersey No Drawing. Application January 24, 1939,

Serial No. 252,547 I 8 Claims.

This invention relates to the manufacture of abrasive products such as grinding wheels, discs,

, segments, etc., and more particularly to abrasive products bonded with an organic bond, such as rubber, shellac or a synthetic resin.

The prime object of my present invention is tov produce organic bonded abrasive products of greatly improved durability and possessing a' cool cutting characteristic. This I accomplish by indurating such abrasive products with a material which makes them self-lubricating while in abrading service.

The value of lubrication during abrading or grinding action is well known. So-called cutting oils are commonly used when grinding is done wet. In dry grinding, lubrication has been resorted to even in such a crude manner as having the operator occasionally smear the abrading surface of the grinding wheel with grease or oil. Another more positive method for providing lubrication is by filling or impregnating. the pores or voids in grinding wheels with-resins, waxes, or pitches, which fluidize and exude during grinding as the result of generated heat.

These known methods of providing lubrication have obvious disadvantages. The filling or impregnating method is limited to a narrow range of grinding wheels due to several reasons. Such wheels must possess pore or void space to carry the lubricant. In general such filled wheels are limited to those bonded with inorganic bonds such as silicates-or clays, since the filling or impregnating is done after such wheels have been fired or hardened to size and form, this'type of wheel being unaffected by the heat needed to impregnate the waxes, etc. Another limitation of this method is the inability to provide lubricants of selected melting points/ranging from 100 to 300 C. or higher.

In accordance with my present invention, it

becomes possible to produce organic bonded abrai sive products with a lubricant incorporated therein in situ during the process of forming the abrasive product. This makes it possible to carry such lubricants in abrasive products with relatively no pore space as well as in those classed as very porous. The quantity and melting point a of the lubricant may be controlled at will and the lubricant may accordingly be predeterminede ly selected tov suit any of a varietyof types and kinds of abrasive products. Also the lubricants are of such a nature that they act partly as a bond for the abrasive particles; in abrasive use of the product, the lubricants become charged with a portion of dislocated or fractured abrasive 55 rubber and shellac.

particles which normally would be wasted during the life of the abrasive product, This latter v feature is especially significant if an expensive abrasive such as diamond bort is used.

I, have discovered that to accomplish these objects of the present invention, certain low melting point metals and alloys may be' made to 1 serve as lubricants for abrasive products and may be incorporated in situ in such products. It is now possible to obtain commercially metals such as lead, tin, bismuth, antimony, cadmium. or alloys thereof, such as solder, etc., in a line state of subdivision. These metals and alloys are com-. monly known as disintegrated metals and may vary in screen size from #10 to #325 mesh. It

is well known that alloys of certain metals, de-

pending on the proportions and number of the metals, can be produced to practically any melting point within, a certain range, for example 55 to 327 C. I take advantage of this fact by.

selecting for a given type .and kind of abrasive product, an alloy or metal which has a melting point generally at and'preferably somewhat under the temperature range developed during its grinding operation and incorporatingsaid metal or alloy in the bond of the abrasive product in the form of a subdivided or disintegrated metallic filler. I

of metals or alloys with the melting point and proportions of each. I do'not limit myself to these, as other combinations are Just as satisfactory, and I'may even use ductile metals or alloys of much higher'melting points, as for ex- These lubricant serving metals or alloys may be predeterminedly selected to suit the particular type and kind of organic bonded abrasive product manufactured. This is illustrated by the examples given hereinbelow of the manufacture of abrasive products bonded with synthetic resin,

In predetermining the par- The following table illustrates a selected range ing this selection. the metals which melt at' approximately the grinding temperatures evolved congeal easily as they leavecontact with the work being ground, and in so congealing, rebond any loose or fractured abrasive particles for service again. which, under ordinary conditions, would be lost. 7

To illustrate the selection of a. metal or alloy for use in a synthetic resin bonded high speed cutting ofl wheel, the preferred metal or alloy selected would be in the range of No. 'l to No. 9 in the above table. This type of wheel removes metal very rapidly with a resultant temperature rise in the metal being cut to a degree where it may be heated to a cherry red; this condition would, therefore, indicate the use and selection of a fairly high melting point metal or alloy, roughly in the range of 200 to 300 C.

As an example of such a synthetic resin bonded grinding wheel made according to the invention. I take 75 parts of a potentially reactive synthetic resin in pulverized form, into which is stirred or otherwise mixed 35 parts by weight of disintegrated tin powder. In another container I take 700 parts of No. 30 abrasive in the form of artiflcial alumina to which I add 25 parts of a synthetic resin in the liquid phase. In place of the liquid synthetic resin, 1 may use a solvent or plasticizer such as furi'ural, furfuryl alcohol, di-

butyl phthalate, etc. The abrasive and liquid synthetic resin are stirred and intimately mixed until the individual abrasive particles are thoroughly wetted and coated, and to this mass while being agitated is added the previously com-' mingled dry'pulverized resin and disintegrated tin. The entire mass is stirred until the pul-,

verized resin and tin are uniformly suspended on the wetted abrasive particles, forming a loose assay-r4 As an illustration of the selection of a metal or alloy for use in a rubber bonded snagging wheel used for surfacing stainless steel billets,

the melting point range selection would fall between Nos. 3 and '4 in the above table, inasmuch mensions and molded under pressure, cold or hot. The formed wheel is.discharged from the mold and subsequently baked in an oven to indurate the bond, at a temperature ranging from 175 to 350 F. inclusive.

The performance of an abrasive product such as a wheel oi" this type utilizing an alloy or metal in the range of Nos. 7 to 9 for lubrication, contrasted with the same type of wheel (synthetic resin bonded) without the alloy or metal, exhibits some outstanding features or characteris tics. A wheelwhich does not contain the disintegrated metal acting as the lubricant heats the metal pieces cut off by the wheel to a cherry red,badly discoloring such pieces. An identical wheel containing the disintegrated metal acting as a lubricant produces cuts which are waterwhite in color, having no discoloration. The second wheel thus exhibits a free and cool cutting characteristic. This second wheel also shows increased durability, in the order of a increase in life, this added durability being the result of operating at much lower temperatures, due to the lubricating effect of the incorporated disintegrated or comminuted metal. This operation at lower temperatures greatly reduces the destroying effect of the heat on the organic bond. The congealing of the lubricant-metal particles as the as these wheels generate lower grinding temperatures than theabovementioned type of synthetic resin bonded wheel.

As an example of such a grinding wheel utilizing rubber as the bonding medium, I take parts by weight of crude rubber, 45 parts of sulphur, 51mm; of calcium oxide, and 50 parts of a disintegrated alloy, shown in the above table as No. 3. To the above is added 1000 parts of No. 14 abrasive in the form of artificial alumina,

and the whole m ss is mixed on differential rolls,-

commonly known as rubber mixing rolls. The slab of mixed stock is shaped by cutting or otherwise and molded under heat and pressure at a temperature of approximately 320 F. to vulcanize the rubber bond. When utilizing rubber, I may use other forms, such as latex, or rubber in the form described in U. 8. Patent No. 1,990,- 737.

The performance of such a rubber bonded wheel containing the lubricant-alloy contrasted with the same type oi wheel without the lubricant-alloy, also shows outstanding features or characteristics. The wheel containing the disintegrated lubricant-alloy shows an increase in durability of 30% when compared with an identical wheel not containing the lubricant-alloy, the metal ground thereby being practically white and uncolored as compared with the metal ground with the contrasting wheel which shows a ground surface containing blue and brown streaks, indicating the higher temperatures evolved where no lubricant-metal is employed. Again in this case, the lubricant-metal present in the wheel reduces the operating or grinding temperatures to a degree eliminating burning of the metal being operated on, the temperature of the wheel itself being reduced to such an extent that the rubber bond is not disintegrated or.

destroyed as rapidly, resulting in greater duratended for grinding or surfacing hardened steel,

alloy listed as No. 1 in the table'would be the proper selection. As shellac bonded wheels are primarily intended for grinding or surfacing purposes where a'minimum amount of generated heat can be tolerated, the lubricant therefor should be one that would melt and would be available for use at very low temperatures. In this case, alloy No. l melting at 55 C. comes into play at substantially under the temperatures wherein hardened tool steels might burn or check due to overheating.

As a specific example of a shellac bonded wheel made in accordance with this invention, I take 100 parts of flaked shellac which has previously been pulverized in'a ball mill to a screen mesh size of at least 80. To this pulverized shellac, I add 50 parts of alloy classed as No. 1 in the above table. In another container, I take 500 pletely suspended upon the wetted abrasive parexhibits the greatly improved durability and the free and cool-cutting characteristics above described.

' I do not wish to limitmyself to any proportions, but find that generally an addition of 10% to 50% of metal or alloy on the organic bond by weight gives the preferred results. I also do not limit myself to particular mesh sizes or any particular metals or combinations thereof, because I have found that they are all applicable to some particular selected purpose. however, I find that I can use straight metals of lead, tin,-copper, or alloys of lead and tin, lead, tin, bismuth and cadmium, lead,.tin and cadmium, and alloys of copper and zinc, in proportions to suit the melting points and ductility desired. I may use abrasives in any form and size, such as natural emery, garnet, artificial alumina, silicon carbide, or crushed commercial diamond.

I claim:

1. An abrasive product comprising abrasive particles bonded with a synthetic resin, the said synthetic resin having incorporated and distributed in situ thereinmetallic particles having a melting point in the range of grinding tempera- I tures of the abrasive product whereby the me- To be more specific,

n On) serve as a lubricant in the grinding action of the abrasive product 3. A lubricant incorporated abrasive product comprising abrasive particles bonded with shellac, the said shellac bond having incorporated and distributed in situ therein metallic particles having a melting point in the range of grinding temperatures of the abrasive product whereby the metallic particles serve as a lubricant in the grinding action of the abrasive product.

4. An indurated abrasive 'product comprising abrasive particles bonded with an organic bond, the said organic bond having metallic particles distributed in situ therein, being incorporated in the abrasive product in the indurating thereof, the said metallic particles being in the proportion of 10% to 50% by weight on the organic bond and being selected to have a melting point in the range of grinding temperatures of the abrasive product. I

5. The method of making an abrasive product wihch is self-lubricating at grinding temperatures which consists in mixing abrasive particles with an organic bond and with metallic particles having a melting point in the range of grinding temperatures of the abrasive product, the said metallic particles being thoroughly distributed in the organic bond, and in then molding the mix to shape and. heat hardening the same.

6. The method of claim 5 wherein the metallic.

particles are usedin the proportion of 10% to 50% by weight on the organic bond.

7. A lubricant incorporated abrasive product comprising abrasive particles .bonded with an organic bond and having incorporated and dis-' tributed therethrough metallic particles of a low melting point in the range of grinding tempera-.

particles and the proportion of the metallic particles being less than that 01' the organic bond. JOSEPH N. KUzMIcK.