US2414226A - Method of making metal bonded abrasive tools - Google Patents

Description

Jan. 14;, 1947. 5,.1 EVERETT 2,414,226

METHOD OF MAKING METAL BONDED ABRASIVE TO OLS Filed Aug. 2, 1944 FIG/O 'IIIIII/iii Inventor \s HMUEL M155 EVEREW;

G h p R M Attorney Patented Jan. 14, 1947 METHOD OF MAKING METAL BONDED ABRASIVE TOOLS Samuel James Everett, Thornton Heath, England Application August 2, 1944, Serial No. 547,786

In Great Britain January 27, 1944 This invention relates to material and tools for grinding, cutting, and like processes, and an object of the invention is to provide means whereby expensive abrasive powders, such as diamond powder, may be economically used, although the invention may also be carried into effect by making use of less expensive powders.

According to the invention, abrasive powder is dispersed in a matrix contained in a ductile sheath, and the impregnated matrix is consolidated by steps which include the reduction of the assembly to a wire or fine rod prior to the complete or partial removal of the sheath to expose a consolidated abrasive wire or fine rod that can be used for a variety of purposes. The matrix may consist of a bundle of wires or a roll of metal foil in which the abrasive powder is distributed, and in such a case the consolidation, which is effected by drawing, rolling or swaging the sheath with its contents, results in converting thebundle or roll to a substantially homogeneous mass in which the abrasive powder is dispersed. A minute quantity of flux together with hard solder may be used to assist the consolidation of the mass and then the hard solder may be melted in the annealing or heat treatment that is necessary in the drawingor like process. The solder may, however, be melted by initially heating the assembly of wires or the like. Such use of solder, however, is not essential. Alternatively copper plating the wires may be employed to assistthe consolidation of the assembly; 7

A Variety of ferrous and non-ferrous metals may be used for the aforesaid wires or foil in which the abrasive material is initially distributed. For example, a stainless steel such as that known as Staybrite (18% Cr, 8 to 9% Ni, some C and the balance Fe) may be used, and the sheath, used to hold together the initial assembly, may be of copper. After the drawing process, the copper coat may be removed electrolytically in a copper cyanide bath or by dissolving the copper in nitric acid which will not attack the stainless steel. However, at least part of the copper sheath may be left to facilitate the attachment of the wire to the tool in which it is to be used. Alternatively, brass may be used for the matrix wire and the assembly encased in a steel sheath which, after drawing, can be removed by dissolving in hydrochloric acid. In a third alternative, high carbon steel wires are used for the matrix and a copper sheath is used which may be removed mechanically (i. e. stripped off the abrasive core) or by electrolytic means in an iron plating bath. In the drawing operationsuch annealing may be 12 Claims. (Cl. 51309) employed as is necessitated by the type of wire being drawn and, after drawing, such heat treat ment is employed as may be necessary. The wire impregnated with abrasive material may, after the removal of the sheath, be subjected to a further shaping process. For example, it may be reduced to a line thread of precise dimensions by passing it through accurately shaped rolls.

The invention is not limited to the use of a metal matrix. Instead the matrix in which the abrasive powder is dispersed may be a ceramic powder which is sintered after the reduction process. Thus, the ceramic powder with the abrasive powder dispersed therein, may be packed in a metal tube and the assembly then reduced by rolling, drawing or swaging to the required dimensions. After the reduction process the assembly is heat treated to sinter the ceramic body and the sheath then wholly or partially removed to expose the fine abrasive rod within. If desired, the initial assembly may contain a central metal rod which, in the drawing or like process, becomes afine wire encased in the ceramic material, imparting tensile strength to the ultimate fine abrasive rod. In a modification of this method of carrying the invention into effect, fine wires around which the abrasive powder is dispersed, or fine wires that have already been impregnated with abrasive material by a method according to the invention, are packed round the rod, and the ceramic powder is omitted entirely. Then the initial assembly comprises a rod round which the fine wires and abrasive powder are packed and the sheath surrounds this assembly.

. In this arrangement oil may be used as an initial adhesive to cause the abrasive powder to adhere to the rod and wires. Cellulose lacquer, flour paste or other cement may be used in place of the oil. Such adhesives may also be used in those assemblies mentioned above in which a bundle of wire or a roll of metal foil is used. However, such adhesives are not essential and the powder may be applied simply by moistening the wire, or even dry, but in this case the results are not quite so uniform.

Alternative abrasive powders are powdered Nitralloy powdered tungsten carbide, and powdered Norbide, the latter consisting essentially of 134C and containing 78% B, 21% C and 0.14% Fe.

In order that the invention may be clearly understood and readily carried into efiect, various methods in accordance therewith will now be described with reference to the following Figures 1 to 6. The nature of these figures is described below in the course of the enunciaticn of the following specific examples of methods by which the invention may be performed.

Example 1 A copper wire of 0.010 inch diameter is cut into lengths and these are dipped in a mixture of trichlorethylene and oil and withdrawn. Then the trichlorethylene evaporates and leaves a trace of oil on the wires. The latter are then rolled in a 150 mesh diamond powder which is caused by the oil to adhere to the wire and the lengths of wire are then bundled together to form a. bundle of approximately a quarter of an inch diameter. The bundle is then put in a steel sheath having an outside diameter of slightly more than inch. This assembly is then heated to approximately 600 C. to remove the'oil. .The assembly is then as shown diagrammatically in perspective in Figure 1 and comprises a circular bundle of wires I contained in a steel sheath 2. In practice, of course, the bundle of wires is covered substantially along its whole length by the sheath 2, but in Figure 1 part of the sheath is shown removed, the better to show the wires.

The assembly is then drawn to a size such that the material within the sheath 2 is approximately 1.5 millimetres diameter. This reduction is shown diagrammatically in Figure 2 in which a die 3 is shown in section. This figure being diagrammatic, shows the reduction to take place in one drawing operation but, in practice, a series of such dies having their respective apertures decreasing insize are used to effect the required reduction in diameter. In the example being considered the assembly is reduced by approximately 20% and then annealed and then reduced by a further 20% and then once more annealed and so on. The annealing is carried out at 600 C. approximately. After the final reduction a further annealing process takes place and the sheath is removed either electrolytically or, preferably, in hydrochloric acid which does not affect the copper.

The aforesaid drawing operation consolidates the individual wires into a single length of copper wir impregnated with powdered diamond and this abrasive length is exposed for use when the sheath has been removed.

Example 2 This is the same as Example 1 but the wires are of high carbon steel and each is 0.012 inch in diameter. The high carbon steel contains approximately 1% carbon. After the diamond powder has been applied, the wires are bundled together and inserted into a copper sheath. In the drawing operation the assembly is annealed at 700 C. after every 20% reduction in diameter, the annealing being for minutes to soften the material and assist in the adhesion of the wires to each other. The reduction operations reduce the assembly to about one sixth of its initial diameter. After the reduction process thecopper sheath is removed electrolytically in a cyanide copper bath.

Example 3 This is the same as Example 1 or Example 2 4 and tin are sintered and assist in consolidating the mass of wires and diamond powder.

Example 4 This may be regarded as the same as any one of Examples 1 to 3 but with the following differences.

=The'abrasive powderconsists of the steel alloy known as Nitralloy L. K. 7 which comprises 0.20% C, 0.35% Si, 0.65% Mn, 1.60% Cr, 1.10% Al, 0.20% Mo. A sheet of this material, 0.015 inch thick, is treated with ammonia gas, in known manner, to harden the material right through. The sheet is then converted into powder by continuously milling the edge of the sheet. Alternatively the alloy is first milled and the powder then treated with ammonia gas. Next the powder is sifted to select particles of the required size, say mesh.

The high carbon steel wire or Staybrite wire must be softened to prevent it from powdering the abrasive still further. The abrasive isnot softened by a temperature of GOO-700 C. and the wire may, therefore, be softened by doing the drawing process in the vicinity of these temperatures. This heating renders the resulting abrasive wire very homogenous.

Example 5 Example 6 A powder is packed in a steel sheath as shown in'the diagrammatic cross section through a portion of the length of such an assembly in Figure 4. The powder 6 consists of a mixture containing 45% frit or powdered glass, 5% 150 mesh. die amond powder, 1% starch, about 5% humidity and the remainder talc. This powder is packed into a mild steel sheath 1 which isplugged at each end to maintain the assembly compact. Theoutside diameter of the initialsheath is approximately half an inch.

The assembly is then drawn or rolled till its outside diameter is approximately onetenth of an inch. The annealing necessary in this drawing or rolling is done at a temperatureof about 550 C. Next the material is heated .to about 750 for thirty minutes to melt the frit or powdered glass and thereby consolidate the material inside the long tube. The latter is then removed but a portion of the metal tube may be left adhering to the ceramic rod to enable it to be soldered to the body of a tool. The aforesaid proportions of the ceramic powder are not critical. Furthermore, alternative materials may be used. For example, there may be used instead of the tale a ceramic material such as the hydrated aluminium silicate known as 'pyrophyllite, or a powdered fired porcelain. The temperature'at which the fusing takes place depends on the kind of frit or powdered glass used in the mixture.

The steel sheath should have the same 00* efficient of thermal expansion as thepowdered material within, or the co-eificient of :expanslon should be slightly less so that the powderis com pressed slightly during the annealing that is necessary during the. drawing operations. I The steel must also be chosenso that the annealing temperature is not so high astomelt the frit.

:"Emample 7 This is the same as Example 6 but, as shown in Figure 5, a central high carbon steel rod 8 is embedded in the powder. This rod after the reduction of the diameter of the assembly serves as a wire core for the ceramic material and imparts tensile strength thereto. Alternatively the into lengths from each of which the core and sheath-are simultaneously removed so as to leave a tubular rod suitable ior trepanning in dentistry or cutting ceramic materials.

Example 8 This example is shown diagrammatically in Figure 6. A rod 9 of about three sixteenths or an inch'di'ameter is dipped in a mixture of oil and trichlorethylene and the latter is, as in Ex ample 1, allowed to evaporate Fine wires 94:: are similarly treated. The oil is used as an adhesive to cause diamond powder to adhere to the rod and fine wires. The latter are then packed round the rod and the assembly is then inserted in aftube H! which may be of coppe. nickel-silver or nickel. The thickness of the tube wall depends on the size of the granules of abrasive. For example, for 150. mesh diamond .powder a tube wall having a wall thickness of 0.010 inch may be used.

The assembly is then reduced by a drawing or analogous process, but is first preferably placed.

in a further case H of mild steel. The annealing during the drawing operations is carefully con trolled (at about 700 C. for 10 minutes) so that it is efiected at a high enough temperature but not so high as todestroy the structure of the metal or turn the diamond powder to another form of carbon. a

Then when the steel case, if used, has been.

wholly removed and the inner sheath partly removed, a strong wire is exposed having its surface impregnated with diamond powder which adheres strongly thereto. Clearly there is economy in diamond powder because this is limited to the outer portionsof the wire.

It is to be understood that in the foregoing examples the drawing or analogous]operations may be accompanied by a shaping process to provide an abrasive wire of a particular cross-sec tion, such as a square cross-section. Furthermore, lengths of the finished wire may be swaged to form files, broaches and so forth.

Various applications or the fine wire and rods made in accordance with the invention will now be described with reference to the diagrammatic Figures '7 to 11 of the accompanying drawing.

The ends of a length of fine wire made in accordance with any one of the above Examples 1 to 4 or Example 7 are joined together to form an endless band saw. Such a saw i2 is shown in Figure 7 and passes round driving driven pulleys l3 and i4. Alternatively single lengths of such wire can be used in a fret saw for cutting ceramic material. Wire made in accordance with the above Example '7 is particularly useful for this purpose and wire made in accordance with Examples hand 6' can also be used in fret :saws.

- Figure 8 is a vertical section through a. rotary grinding wheel having a circular core [5 on the periphery of which is wound wire l6 made in accordance with any one'of Examples l to 4 and rolled to square cross-section. The wire is preferably soldered to the wheel. For a face grinding wheel the wire is secured to one of the faces of the core it instead of its periphery.-

Figure 9 is a vertical section through a thread grinding wheel. This has a metal core l1. round the periphery of which are soldered parallel rings of wire made in accordance with any one of the above Examples 1 to 4 and formed to the cross section shown in Figure 9,

Figure 10 showsa vertical section through a circular cutting disc for use on glass, stone or other ceramic materials; Figure 10 .is drawn on a substantially enlarged scale (as also is Figure 9). A thin disc 19. has a shallow groove out in its periphery, and an abrasive impregnated wire of a diameter slightly greater than the thickness of the disc is soldered in the groove so as to provide a rim which bulges outwards slightly on each side of the disc, Instead of soldering the wire to the disc, the ends of the wire may be secured in a radial slot formed in the disc, the wire being held tightly in position by a spring in the slot.

Wire made in accordance'with the above Example may be used in the manufacture of" small grinding wheel heads, such as dental burrs. A comparatively large diameter wire is made use of and this is swaged or worked to the shape re-,

quired for the head before the sheath is removed and the resulting implement is treated with acid to expose the diamond points. Figure 11 shows such ahead 2! on an enlarged scale. The head is attached to a spindle22. There are even more ways of making. use of the abrasive impregnated wire with which this invention is concerned. For example, it can be used on an adjustable lapping tap, Yet again. it may be cut up and bundled'to form a brush. Such abrush may be used for frosting. glass or for decorative purposes, or it may be-used for smoothing-and finishing surfaces. Another use for this form of. brush is in dentistry, the end of the brush being carefully shaped so that it can beused as a flexible cutting burr for cleaning caries in teeth.

Although the invention has been described above primarily inrelation to the production of wire and fine rods, it can be applied to the production of heavier gauge materials, For instance,

in Example 2 the high carbon steel wires and diamond powder may be packed into a copper sheath of; three inches diameter and one quarter of an inch wall thickness. This'assembly is then drawn down to one inch diameter. If, as in Example the abrasive ismesh diamond powder, the initial wires may be twenty thousandths of an inch diameter, but for coarser. powder stouter wire may be used. If a tubular rod is required, the initial assembly may be furnished with a mild steel core which, after the assembly has been drawn down to the required size and cut into lengths, may be removed by drilling, the outer coupper sheath being removed electrolytically.

I claim:

1. A method of forming an abrasive wire of rod, comprising the steps of dispersing an abrasive powder in a matrix, inserting said. matrix containing abrasive powder in a ductile sheath,

7 consolidating said matrixby elongating and sub;- stantially reducing the cross-sectional area of the assembly comprising said sheath and said powder impregnated matrix contained therein, and exposing the resulting consolidated abrasive impregnated wire or rod by removing the material of said sheath.

2. A method of forming an abrasive wire or rod, comprising the steps of dispersing an abrasive powder among a bundle of metal wires, in serting said wires and powder in a ductile sheath, -consolidating said wires and powder by elongating and substantially reducing thepross-sectional area of the assembly comprising said sheath and said powder impregnated bundle contained therein, and exposing the resulting consolidated abrasive impregnated wire or rod by removing the material of said sheath.

3. A method of forming an abrasive wire or rod, comprising the steps of dispersing an'abrasive powder in and around a roll of metal foil, inserting said roll with said abrasive powder in a ductile sheath, consolidating the convolutions of said roll and said powder by elongating and substantially reducing the cross-sectional area of the assembly comprising said sheath and said powder impregnated roll contained therein, and exposing the resulting powder impregnated wire or rod by removing the material of said sheath.

4. A method of forming an abrasive wire or fine rod, comprising the steps of mixing an abrasive powder with a ceramic powder, filling a duotile sheath with said mixture and thereby reducing the cross-sectional area of the assembly'ineluding said sheath and powder, heating said assembly to sinter said ceramic powder, and expos- .ing the sintered abrasive impregnated wire or fine rod by removing the material of said sheath. 5. A method of forming a fine abrasive rod comprising the steps of mixing an abrasive powder and a ceramic powder, packing said mixture inside a sheath and around a ductile metal rod within said sheath, substantially elongating and thereby reducing the cross-sectional area of the assembly comprising said mixture, said sheath and said ductile metal rod, heating the elongated assembly to sinter said ceramic powder, and removing the material of said sheath to expose the sintered ceramic material containing abrasive powder and internally reinforced.

6. A method of forming anabrasive tubular rod, comprising the steps of dispersing an abrasive powder in a matrix, packing said matrix containing said powder around a ductile metal core and inside a ductile sheath, consolidating said matrix by elongating and substantially reducing the cross-sectional area of the assembly comprising said sheath, said powder-impregnated matrix and said core, and subsequently removing said sheath and said core.

7. A method of forming an abrasive wire or rod, comprising the steps of dispersing diamond powder in a matrix, inserting said matrix containing diamond powder in a ductile sheath, consolidating said matrix by elongating and sub- 8 stantially reducing'the cross-sectional area of the assembly comprising said sheath and said diamond impregnated matrix contained therein, and

' exposing the resulting consolidated abrasive impregnated wire or rod by removing the material of said sheath. V

3. A method of forming an abrasive wire or rod, comprising the steps of dispersing diamond powder among a bundle of copper wires, inserting said wires and powder in a steel sheath, consolidating said wires and powder by elongating and substantially reducing the cross-sectional area of the assembly comprising said sheath and said powder impregnated bundle contained therein, and exposing the resulting consolidated abrasive impregnated wire or'rod by removing the material of said sheath by dissolving in hydrochloric acid. a r i 9. A method of forming an abrasive wire or rod,

comprising the steps of dispersing diamond powder among a bundle of high carbon steel wires, inserting said wires and powder in a copper sheath, consolidating said wires and powder by elongating and substantially reducing the cross sectional area of the assembly comprisingsaid sheath and said wires with diamond powder dispersed among them, and exposing the resulting consolidated abrasive wire or rod by removing the material of said sheath by electrolytic cyanide copper bath.

10. A method of forming an abrasive wire or rod, comprising the steps of mixing powdered copper, tin and diamond, dispersingthe said mixture among a bundle of steel wires, inserting said wires and powder in a copper sheath, consolidating saidwires and powder by elongatingand substantially reducing the cross-sectional area of the assembly comprising said sheath, said mixture and said wires, heating said assembly to sinter said copper and tin, and exposing the resulting consolidated abrasive impregnated wire or red by removing the material of said sheath.

11. A'method of forming an abrasive wire or rod, comprising the steps of forming a nitrogen hardened steel powder, dispersing said powder amonga bundle of steel wires, inserting said wires and powder in a ductile sheath, consolidating said wires and powder by elongating and substantially reducing the cross-sectional area of the assembly comprising said sheath and said powder impregnated bundle contained therein, and exposing the resulting consolidated abrasive impregnated wire or rod by removing the material of said sheath. 12. A method of forming an abrasive wire or rod, comprising the steps of dispersing an abrasive powder in and around a roll of brass foil, inserting said roll with said abrasive powder in a high carbon steel sheath, consolidating the, convolutions of said roll and said powder by elongating and substantially reducing the crosssectional area of the assembly comprising said sheath and said powder impregnated roll contained therein, and removing said sheath by solution in hydrochloric acid.

SAMUEL J AMES'EVERETT.

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