US2170164A

US2170164A - Art of setting diamonds and making diamond tools

Info

Publication number: US2170164A
Application number: US190956A
Authority: US
Inventors: James M Stone; Rutherford H Taylor
Original assignee: J K SMIT SONS Inc
Current assignee: J K SMIT SONS Inc
Priority date: 1938-02-17
Filing date: 1938-02-17
Publication date: 1939-08-22
Anticipated expiration: 1956-08-22

Description

Aug. 22, 1939. J. M. STONE ET AL 2,170,154

ART OF SETTING DIAMONDS AND MAKING DIAMOND TOOLS Filed Feb. 17, 1938 INVENTORS I Mil/f? 4' BYWM I ATTORNEYS Patented Au 22, 1939 UNITED STATES PATENT OFFICE James M. Stone, Detroit, Micla, and Rutherford B- Taylor, Millburn,

N. J., assignors to J. K.

Sinit Sons, Ino., New York, N. Y., a corporation of New York Application February 1'1, lass, Serial No. 190,956

BOIaims.

Broadly speaking the present invention is directed to the art of setting diamonds and to the manufacture .of diamond tools wherein the diamond is mounted or set in a matrix of metal.

Those persons skilled in the art of manufacturing tools employing industrial diamonds as the cutting element, such as core bits, dressing tools, etc., as well as the users of such tools, are familiar with the fact that in use the mounting, setting or matrix, as well as the diamonds themselves, are subjected to strain and stresses of such magnitude that the diamonds may work loose and unfit the tool for use. Attempts have been made in the past to reset the diamonds, but this usually necessitates repeated heatings with the result that the diamond is deleterlously affected and its usefulness impaired, oftentimes to the extent that the diamond is unfltted for further use.

Various methods have been devised for setting the diamonds initially so that they will not work loose, For example, in one method the diamond is set in a mould and metal cast around it. It will be appreciated that by this method the sudden shock to the diamond when the molten metal contacts it is very likely to injure the "skin of the diamond and reduces its effectiveness as a cutting tool.

Another method suggested for the making of diamond laps, for instance, involves the use of metal powder, the powder being placed about the diamonds and simply subjected to very high pressure. While the matrix thus formed is hard it crumbles and breaks away from the diamond very readily;

In the making of core bits 9. method has been suggested wherein metal powders are placed about the diamonds and subjected to high pressure, after which the mass is heated to a sufflciently high temperature to sinter the metal. One of the metals of this method must have the ability to wet the diamond. so. that upon heating and cooling the metal will cohere to the diamond. We have discovered, however, that in this method the diamond very often splits in the shrinking of the matrix as the same cools down, apparently due to the cohesion between the metal of'the matrix and the surface of the diamond by reason of the wetting of the diamond. Splitting or cleavage of the diamond, of course, unfits the same for use.

We provide a method by the present invention whereby the diiflculties above referred to are eliminated in that the diamonds are not subjected to sudden shock as in method and steps are taken to prevent wetting of the diamond so that we avoid splitting and cleavage of the diamond, and obtain an entirely satisfactory retention of the diamond in its mount or matrix..

With more specific reference to our method, we initially coat the diamond to prevent wetting of the same and in addition the powdered metals which we preferably employ appear to lack the ability'to wet the diamond.

In the practice of our invention and with reference, for clarity of description, to the manufacture of dressing tools for grinding wheels: The diamonds are first coated with a metal powder, such as powdered aluminum which for convenlence of application to the diamonds may be suspended in acetone. The diamonds may be dipped or tumbled in this material or the material applied to the surface of the diamond with a brush. It will be appreciated that this coating is just a mere him over the surface of the stones.

The coated diamonds are then positioned in a mould at desired distances apart, this mould, in the case of dressing tools, constituting the body or head of the holder; An admixture of powdered tungsten and powdered copper is then placed in the mould, care being exercise that the diamonds are completely buried in this powder. We then subject the metal powders to high pressure, of the order of twenty tons per square inch, for instance, after which the ram of the press is withdrawn and the shank of the holder inserted in the mould, its lower end resting upon the mass of pressed metal therein. A ring or collar of welding metal such as copper is then placed about the holder shank, the shank and head of the holder temporarily secured together, and the assembly placed in an oxygen-free furnace where the mass is heated to a temperature of around 2100 F. This-temperature is below the melting point of the tungsten and below the temperature at which the diamonds will be deleterlously affected. but is above the melting point of copper, so that the welding ring is melted and flows down about the sides of the holder shank, eflectively to weld or secure the shank in the holder. The copper of the compressed metal mixture is also melted at this temperature so that the mass upon cooling is converted into a coherent product in which the diamonds are embedded. Wetting of the diamonds, however, has been prevented due to the presence of the aluminum coating, which seems to permit of slippage of the diamonds in the matrix as the molecules of the latter adJust themselves in the heating and cooling stages of the process, so that cleavage or splitting of the diamonds is eliminated. When the mass has cooled it is turned and sand-blasted down to the desired shape and to expose the diamonds.

Apparently wetting of the diamonds is avoided in our process, in that upon examination of diamonds which have been mounted in accordance with our process the surface of the diamonds is found to be as bright and shiny as before treatment; whereas were there any wetting the surface of the diamonds would have an etched appearance or be discolored or pitted;

In the accompanying drawing which is mere- 1y diagrammatic and purely illustrative, we have attempted to show the various steps of our process in the making of a dressing tool.

Fig. 1 illustrates, for example, the first stage or step of our process;

Fig. 2 is a sectional elevational view showing the next, step of our process;

Fig. 3 is a sectional elevational view illustrating the tool after it has been removed from the furnace; and

Fig. 4 is a part sectional elevational view of the finished tool.

Referring to the drawing in detail: 2 designates the body or head of the holder, which in the practice of our process, with respect to the making of dressing tools, functions in the early stages of the process as a mould.

I designates the diamonds to be set. It is to be understood that their number as well as their disposition in the mould or holder head will depend upon the type of tool under consideration. In any event, however, before the diamonds are placed in the mould or holder head they are coated with powdered aluminum suspended in a suitable vehicle such as acetone. An admixture of powdered copper and tungsten, designated 6, is then poured into the holder 2. A formula which we have found gives excellent results is 25 parts by weight of copper to 75 parts by weight of tungsten. This seems to be well suited for all types of dressing tool in general, although these proportions may be varied somewhat if a harder setting is desired. For instance. the copper content may be decreased to 10 parts by weight and the tungsten correspondingly increased to 90 parts by weight.

The powdered metals are then subjected to pressure as, for example, by hydraulic ram 8. The pressure employed may be varied of course, but

I we have found a pressure of twenty tons per square inch gives satisfactory results.

Upon withdrawal of the ram] the shank III of the holder is inserted into the holder head 2, its lower end resting upon the metal mass 6. Welding material, such as a copper strip i2, is then wrapped about the shank Hi, and the assembly temporarily secured together by a wire I4 or other suitable means.

We then place the assembly in a suitable furnace which is free of oxygen, where the assembly is heated to a temperature of the order of 2100 F. The time that the assembly is kept at this temperature may vary somewhat. We have found twenty minutes gives excellent results.

After the heat treatment the assembly is removed from the furnace and the head and shank turned down" or ground down to the shape desired as, for example, to the shape shown in Fig. 4 to expose the diamonds l.

We have found that while the heat treatment at the temperature mentioned is above the melting point of copper but below the melting point of tungsten, it is well below the temperature at which the diamonds will be deleteriously affected. and that the metal powders previously subjected to the tremendous pressure indicated have been converted into a coherent solid mass IS with the diamonds securely held therein. Inasmuch as the surface of the diamonds was initially treated to prevent wetting by the metals of the setting or matrix, cohesion of the metals of the setting to the diamonds is avoided, permitting of a certain amount of slippage of the diamonds as the molecules of the materials of the matrix are rearranging themselves in the heating and cooling stages of the process to eliminate splitting and cleavage of the diamonds. The welding metal II, we find, not only works down betweenthe shank l0 and head 2, as shown at II, but some of it finds its way into the metal mass 8. Actually we have found that the copper content of the matrix may have been increased by as much as 10%.

It will be appreciated that in the practice of our process we obtain the advantages of a setting made by the prior methods employing molten metal, but without any of the disadvantages of such a method, such as the shock to the diamond occasioned by the sudden contacting of molten metal with the surface of the diamond. It will be appreciated also that our process, by preventing wetting of the diamond, avoids or eliminates splitting and cleavage of the diamonds due to cohesion between the diamond and the metal of the setting.

We have found that stones set in accordance with our method are retained satisfactorily in the setting enabling the tool to be used in the usual way over long periods of time without loosening or shifting of the stones in the setting.

While we have described our invention in connection with the making of dressing tools, it is to be understood that the invention is also applicable in connection with the setting of industrial diamonds for otherpurposes, as, for example, in the manufacture of drawing dies, core bits, etc.

It is to .be understood that changes may be made in the procedure above described without departing from the spirit and scope of our invention.

What we claim is 1. The method of setting commercial diamonds and the like, which method comprises coating a diamond with a metal powder, embedding the coated diamond in a mass of metal powders comprising a high melting point metal and a relatively low melting point metal, the coating-metal powder exhibiting the property of resisting etching, discolor-ing or pitting oi the surface of the diamond when the mass of metal powders is heated to the melting temperature of the said relatively low melting point metal, forming the mass in which the diamond has been positioned into a shaped body by cold-pressing, and finally subjecting the shaped body to a temperature above the melting point of the said low-melting point metal but below the temperature at which the desirable qualities of the diamond are impaired.

2. The method of setting commercial diamonds and the like, which method comprises coating a. diamond with a metal powder, embedding the coated di mond in a mass of metal powders comprising a high melting point metal and a relatively low melting point metal, the coating-metal powder exhibiting the property of resisting etching, discoloring or pitting of the surface of the diamond when the mass of metal powders is heated to the melting temperature of the said relatively low melting point metal, forming the mass in which the diamond has been positioned into a shaped body by cold-pressing, and finally subjecting the shaped body, in a space free of oxygen, to a temperature above the melting point of the said low-melting point metal but below the temperature at which the desirable qualities of the diamond are impaired.

3. The method of setting commercial diamonds and the like, which method comprises coating a diamond with a metal powder, embedding the coated diamond in a mass of tungsten and copper powder, the coating-metal powder exhibiting the property of resisting etching, discoloring or pitting oi the surface oi! the diamond when the mass of tungsten and copper powders is heated to the melting temperature 01' the copper, forming the mass in which the diamond has been positioned into a shaped body by cold-pressing, and finally subjecting the shaped body to a temperature above the melting point of the copper but below the temperature at which the desirable qualities of the diamond are impaired.

4. The method of setting diamonds and the like, which method comprises coating a diamond with aluminum powder, embedding the coated diamond in a mass of metal powders comprising a high melting point metal and a relatively low melting point metal, the aluminum powder exhibiting the property of resisting etching, discoloring or pitting of the surface of the diamond when the mass of metal powders is heated to the melting temperature of the said relatively low melting point metal, forming the mass in which the diamond has been positioned into a shaped body by cold-pressing, and finally subjecting the shaped body to a temperature above the melting point of the said low-melting point metal but below the temperature at which the desirable qualities of the diamond are impaired.

5. The method of setting commercial diamonds and the like, which method comprises coating a diamond with aluminum powder, embedding the coated diamond in a mass of tungsten and copper powder, the tungsten and copper being in the proportions of from 25 to 10 parts by weight of copper to '75 to 90 parts by weight oi tungsten, the aluminum powder exhibiting the property of resisting etching, discoloring or pitting of the surface or the diamond when the mass 01' tungsten and copper powder is heated to the melting temperature of the copper, forming the mass in which the diamond has been positioned into a shaped body by cold-pressing, and finally subjecting the shaped body to a temperature above the melting point of the copper but below the temperature at which the desirable qualities of the diamond are impaired.

6. In the production of dressing tools, the method which comprises coating a diamond with a metal powder, embedding the coated diamond in a mass of metal powders comprising a high melting point metal and a relatively low melting point metal contained in the head of the dressing tool, the coating-metal powder exhibiting the property of resisting etching, discoloring or pitting oi the surface of the diamond when the mass of metal powders is heated to the melting temperature of the said relatively low melting point metal, applying pressure to this powdered mass, thereafter inserting the shank of the tool into said head upon the compressed metal mass therein, and with a brazing metal in place about the tool shank subjecting the assembly to a temperature above the melting point of the relatively low melting point metal and or the brazing metal, but below a temperature at which the diamond will be deleteriously afl'ected.

JAMES M. STONE. RUTHERFORD H. TAYLOR.

CERTIFICATE OF CORRECTION.

Patent No. 2,170,161;-

August 22, 19 9.

JAMES PI. STONE, ETAL.

It is hereby certified that the name ofthe assignee in the above numbored patent was erroneously written and printed as J. K. Smit Sons, Inc." whereas said name should have been written and printed as J. K. Smit &: Sons Inc. of New York, N. Y. a corporation of New York, as shown by the record of assignments in this office; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 26th day of September, A. D. 19.39,

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents.

atively low melting point metal, forming the mass in which the diamond has been positioned into a shaped body by cold-pressing, and finally subjecting the shaped body, in a space free of oxygen, to a temperature above the melting point of the said low-melting point metal but below the temperature at which the desirable qualities of the diamond are impaired.