GB1602786A - Drill bushing pump seal or similar articles and method of making same - Google Patents

Description

(54) DRILL BUSHING, PUMP SEAL OR SIMILAR ARTICLES AND METHOD OF MAKING SAME (71) I, EDWARD JOSEPH VOITAS, of 59 De Gray Terrace, Mahwah, New Jersey 07401, United States of America, a citizen of the United States of America, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to articles of manufacture such as drill bushings which are used throughout industry and are commonly incorporated into drill jigs and to the method of manufacturing such articles.

While the principal thrust of the invention is directed toward providing devices which are commonly referred to as drill bushings, it is also within the scope of the invention to provide pump seals, bearings, guide bush ings, spray nozzles and similar articles.

Drift jigs are used to insure the accurate location of a hole, which is to be drilled into a work piece with respect to a fixed reference point or with respect to another hole or pattern of holes. This reference point is used to maintain accurate location of a pattern of holes in the work piece or part which is accurately reproducible over a long production run of such parts. In order to maintain this accurate, small tolerance condition, it is necessary to guide the drills to very close tolerances and to maintain these tolerances throughout the production. This is accomplished by using articles of the invention as drill jig bushings.

The prior art drill jig bushings have been and generally are made of high carbon or alloyed tool steel which have been heat treated to improve hardness. Such bushings provide reasonable drill guidance over their life. The life is relatively short because it is limited by the wear resistance characteristics of the metal. Attempts have been made to improve wear life by using high speed steel of various specialized alloys. These drill jig bushings are much more expensive and leave much to be desired in terms of wear life when they are used. for example, in the drilling of material containing asbestos or other abrasives such as encountered in cast iron.

Alternatively, when long wear life has been the critical element in a production problem, industry has turned to solid tungsten carbide drill bushings. These bushings which are usually solid throughout their cross-section, have several disadvantages.

First and foremost, the cost is about 10 to 20 times that of high speed steel. Second, these parts are brittle and are often damaged dur mg installation in the drill jig or are chipped by the tool itself. Various attempts, having limited commercial success, have been made to fabricate a tungsten carbide liner adapted to be pressed or brazed into a steel or other metal body. These units, too, are quite expensive being about 10 to 20 times the cost of tool steel bushings. Moreover, these units which use tungsten carbide fullyinserted bushings or rings brazed, welded or mechanically held in place in a tool or alloy steel body, have sufficient mass of tungsten carbide so that the coefficient of expansion characteristics of tungsten carbide control the expansion of the bushing. Thus, when the tool steel tools are used with these bushings, the difference between the coefficient of expansion of the bushing and the coefficient of expansion of the tool, may produce tool seizure. Tool seizure results from the fact that as the tool heats up, its coefficient of expansion is such that it expands at twice the rate of the solid carbide bushing or the one with large inserted masses of tungsten carbide in the form of sleeves or rings.

Therefore, initial clearance must be su i- cient to avoid this with close tolerance being sacrificed at least during the early period of operation until the tool expands sufficiently to close the excess tolerance. When there are very accurate tool guiding requirements, the tool may be seized and bound after it has been operated for a while.

The production cost of solid tungsten carbide bushings is high because, among other things, the part must be pressed to shape and sintered and then must be ground with a diamond grinding wheel in order to complete the finishing process. Another important disadvantage, which results from the use of solid tungsten carbide is the inability to manufacture drill bushings with a variety of outside shapes. This is inherent in the material characteristics since solid tungsten carbide is difficult to grind and is brittle.

There is thus a need for an article, such as a drill bushing or a pump seal, which will maintain its accuracy and possess a longer life than the presently used articles.

According to one aspect of the present invention there is provided a method of manufacturing an article for accurately confining a cylindrical element rotating about its longitudinal axis, which comprises; forming from steel a blank or body having the desired outer and inner configurations and a central longitudinal axis; cleaning the blank so that it is free of contaminants; forming an adhesive of boric acid dissolved in distilled water and of a first material having a hardness in the range of from 59 to 67 Rockwell C; applying the wet adhesive to the inner surface of the blank; adding particles of a second material having a hardness in the range of from 84 to 9 Rockwell C to the wet adhesive so that the wetted surface captures the second material particles; drying the blank at a temperature in the range of from 350" to 4000F for a time sufficient to remove the water and moisture from the blank; adding further wet adhesive to the coated inner surface of the blank; adding powder of the first material to the wet adhesive on the coated inner surface so that the wetted surface captures the first material powder; drying the blank at a temperature in the range of from 350" to 4000F for a time sufficient to remove the water and moisture from the blank; raising the temperature of the blank to a temperature in the range of from 1925 to 2025" and holding the blank at the temperature in the range of from 1925 to 20250F for a period in the range of from 3 to 5 minutes; tempering the blank for a time and at a temperature appropriate for treating the body of the blank; and finishing the blank to the desired size and smoothness.

According to another aspect of the present invention there is provided a method of manufacturing an article for accurately confining a cylindrical element rotating about its longitudinal axis, which comprises; forming a blank having the desired outer configuration; cleaning the blank so that it is free of contaminants; drilling a blind longitudinal opening in the blank; forming an adhesive of boric acid dissolved in distillled water and powder of a first material having a hardness in the range of from 59 to 67 Rockwell C; applying the adhesive to the surface of the longltudinal opening; precoating particles of a second material having a hardness in the range of from 84 to 93 Rockwell C with the adhesive; filling the longitudinal opening with the precoated articles of the second material; drying the blank at a temperature in the range of from 350" to 4000F for a time sufficient to remove the water and moisture from the blank; adding adhesive to the longitudinal opening; adding a measured amount of particles of the first material at the top of the longitudinal opening; drying the blank art a temperature in the range of from 350" to 4000F for a time sufficient to remove the water and moisture from the blank; raising the temperature of the blank to a temperature in the range of from 1925 to 202SF and holding the blank at the temperature for a period of time in the range of from 3 to 5 minutes; tempering the blank for a time and at a temperature appropriate for treating the body of the blank; removing the top and bottom of the blank to thereby expose the ends of the filled longitudinal opening; piercing an opening through the filling longitudinal opening; finishing the blank to the desired size and smoothness.

According to a further aspect of the present invention there is provided an article of manufacture for accurately confining a cylindrical element rotating about its longitudinal axis, produced by the hereinbefore described method, comprising a body formed of steel and having a longitudinal opening therein; a liner of particles having a hardness in the range of from 84 to 93 Rockwell C in a matrix of material having a hardness in the range of from 59 to 67 Rockwell C bonded to at least a portion of the longitudinal opening in the body and having an opening therein to receive the cylindrical element and to permit said cylindrical element to rotate freely therein; the dimensions and material of the liner being such that the liner and the body together have a coefficient of thermal expansion substantially equal to that of the cylindrical element thereby to accurately maintain the position of the cylindrical element as it rotates and confine it to rotation about its longitudinal axis.

Such an article will maintain the design clearance between complementary moving parts because the body is steel and the coating whose thickness ranges from .003"-.005" is composed of tungsten carbide particles distributed throughout a matrix of nickel chrome. This allows the coating to have substantially the same coefficient of expansion as the tool steel body.

Such an article may have a surface with the abrasion and wear resistance of similar articles formed of solid tungsten carbide, be economical to produce and sell for a fractior of the cost of tungsten carbide drill busl- ings.

A bushing can be provided which has exposed tool steel at the entering end to thereby avoid tool damage that could occur in the event of an off-center tool came in contact with tungsten carbide of conventional solid tungsten carbide or inserted sleeve or ring type bushings. Beyond the bellmouth or tapered entry side of the drill bushing the thin layer of tungsten carbide provides the highly wear resistant surface.

Such an article can have a body formed of alloy or tool steel and is provided with a thin coating of tungsten carbide particles which are metallurgically bonded in a matrix of nickel chrome to the body.

In such an article the tungsten carbide particles of controlled micron size are contained in a matrix of nickel chrome so that the matrix has about the same coefficient of thermal expansion as the body and the drill or rotating shaft inserted in the bushing.

Such an article can have as good or better wear characteristics when compared to solid tungsten carbide articles and also can be less likely to chip or crack in use or during installation.

An article such as a bushing can be provided which has improved lubrication properties because there is produced within the bushing a surface which is unlike a thin solid surface and which has the interstices between the micron size particles of tungsten carbide filled with matrix material. This is accomplished by controlling the amounts of matrix materials sufficient to insure metallurgical bonding to the bushing proper and avoiding filling all the voids or interstices between the particles. Thus, interstices are left for the passage of oil or lubricants between the tungsten carbide particles even while a solid shaft or tool having a close fit is rotated within the bushing.

An article can be provided wherein the inside diameter is lined with a thin coating of tungsten carbide and a controlled amount of matrix which when finished to the proper inside diameter dimension leaves a multiplicity of tool bearing points which are generated by the partial cutting of the particles to a condition wherein each particle, so exposed, provides a bearing point while, at the same time, leaving the interstices between particles free to allow lubricant to flow freely.

Broadly, one article of the invention comprises a hollow steel body with various configurations, having a coating of a matrix of a material such as nickel chrome added to the inside diameter thereof. Micron size particles of tungsten carbide are uniformly distributed throughout the matrix which provides a metallurgical bond to the steel body and a metallic bond to each such particle.

The coating, as applied, has a thickness of the order of between .006" and .008". Final finishing reduces the thickness to the order of approximately .003".

While tungsten carbide particles are preferred, particles of other materials having a hardness in the range of from 84 to 93 Rockwell C may also be used. Similarly, a matrix of material having a hardness in the range of from 59 to 67 Rockwell C may be used in place of the preferred nickel chrome material.

The body and the matrix have about the same coefficients of thermal expansion so that there is little internal strain introduced as the articles heat up from friction during use. Moreover, the article has almost the same coefficient of thermal expansion as that of the drill or shaft which rotates in the hollow opening so that more accurate fitting is initially posslble and there is no binding as the temperature rises during use. The term which is normally used to describe the condition, which occurs when the tool expands at a much faster rate than the bushing, is "seized" or "frozen" which indicates metal-to-metal interference. It is also within the contemplation of the invention to provide an article having a surface which has interstices and voids between the particles of tungsten carbide to allow oil, lubricants or coolants to flow freely or be pumped between the inside wall of the bushing and the shaft or tool. Articles of the invention avoid freezing or seizing while still maintain ing close clearance between tool and bushing.

The method of manufacturing articles of the invention for producing bushings of .140" diameter or larger broadly comprises applying a thin coating of selected mesh pam ticles of tungsten carbide to the inner longitudinal opening of the body, adhering the particles in place with a suitable adhesive and then applying successive layers of nickel chrome matrix or other suitable alloy and fusing it metallurgically in a vacuum or hydrogen controlled atmosphere or salt bath furnace to allow the matrix material in its liquidus state to fill the interstices between the tungsten carbide particles and also diffusion bonding itself to the inner longitudinal wall or face, as well as providing a bond to the tungsten carbide particles. The body is quenched for heating directly from the fusion stage and annealed.

The inside of the body is rough honed, or ground, then finish honed or lapped to its proper inside diameter. Then the outside of the body is ground to its proper diameter and configuration.

The method of the invention for producing small size bushings differs slightly from that for large bushings. A bushing with a blind hole has adhesive applied to its inner wall, the hole is fully filled with micron size tungsten carbide particles which have been pretreated with a solution of adhesive mat erial which has nickel chrome powder sus pended in solution throughout, this insures proper fluxing and bonding to the bushing and of the tungsten carbide to the matrix to be added to the next step. At this step, the cup shaped portion of the bushing is filled with nickel chrome or other suitable alloy and is treated with adhesive, the article is placed in a vacuum furnace hydrogen controlled atmosphere furnace or salt bath furnace and when the temperature is brought up to the liquidous state of the matrix material, the excess of matrix material fills the voids and interstices to form a solid plug of tungsten carbide particles, fully bonded to the inner longitudinal wall and to itself. The body's outside diameter is ground after heat treating and the hold is pierced to an accurate diameter with an electrochemical machine, an electro-discharge machine or a laser beam and is then honed or lapped to its final accurate diameter and surface finish. In the industry, surface finish is designated in units of rms.

In the accompanying drawings, forming a part of this application and in which like numerals are employed to designate like parts throughout the same: FIG. 1 is a block diagram showing the steps in the method of forming articles of the invention having an inside diameter of the order from about .140 up to several inches; FIG. 2 is a perspective view of a machine used for carrying out some of the steps of the method of the invention used in the manufacture of articles having an inside diameter of the order of .140" to .750"; FIG. 3 is a sectional view, taken on lines 3-3 of FIG. 2, viewed in the direction of the arrows; FIG. 4 is a view of the machine of FIG. 2 showing its use in the manufacture of articles of the invention; FIG. 5 is a view partly in section, showing a modified machine for use in the manufacture of articles having an inside diameter of the order of .750" to 6" or more; FIG. 6 is an enlarged sectional view of a portion of an article of the invention having a dense coating on the inner surface; FIG. 7 is a view, similar to that of FIG. 5, showing an article of the invention having interstices between the tungsten carbide particles; FIG. 8 is a sectional view of an article of the invention having a head and a coating on the inner surface and on a portion of the head; FIG. 9 is a view similar to that of FIG. 8 of a non-headed article of the invention having a coating on the inner surface and on a portion of the top of the article; FIG. 10 is a view similar to that of FIG. 8 of a headed article of the invention wherein the head is uncoated; FIG. 11 is a view similar to that of FIG. 9 of a non headed article of the invention wherein the upper portion of the inner surface is uncoated; FIG. 12 is a view similar to that of FIG. 8 of a headed article of the invention such as a pump bushing wherein the inner surface and top surface of the head of the article are coated; FIG. 13 is a block diagram similar to that of FIG. 1 showing the steps in the formation of small articles of the invention having an inside diameter of the order of .005" to .140"; FIGS. 14-17 illustrate some of the steps used in the manufacture of articles of the invention having inside diameters of the order of .005" to .140"; and FIGS. 18 and 19 illustrate two of the steps used in the manufacture of articles of the invention having inside diameters of the order of .005" to .140".

In the drawings, wherein, for the purpose of illustration, are shown various embodiments of the invention, the numeral 30 (FIG. 1) designates the step of forming and cleaning a steel blank. Step 30 is preferably carried out by machining the part on conventional machine tools. The part must be chemically clean and free of oil, dirt or other contaminants. A preferred method of cleaning is to batch clean the articles in a hydrogen atmosphere furnace. This results in metallurgical cleansing of the articles preparatory to the next step.

After the foregoing procedure has been carried out, boric acid dissolved in distilled water (step 32) and micron size powder of nickel chrome (step 34) are combined to form an adhesive (step 35). The adhesive has the consistency of heavy oil. The consistency can be controlled by varying the amount of nickel chrome powder and can be reproduced by accurate control of the ratio of fluid measure to weight of the nickel chrome. Such control insures repetitive consistency of the amount of nickel chrome in suspension. The adhesive so formed is added to the inner surface of the piece (step 36). Next (at step 38), the tungsten carbide particles are applied to the wet adhesive coated surface. The tungsten carbide particles are added while the adhesive is still wet so that they are caught in a manner similar to the result obtained when sugar comes in contact with a wet finger. The amount of such adherence will depend on the mesh size of the particles. The piece is now dried (step 40) at a temperature of the order of 3500-4000F for a period of time required to bring the part up to uniform temperature and sustained for such time as is required t evaporate all the water and moisture out of the adhesive. To dry articles of the invention on a production basis, the drying (step 40) is done in a conveyor type oven at about 3500-4000F. The heating time depends on the mass of the part but the heating time and temperature must be sufficient to insure that all water and moisture is evaporated and removed from the part. Now, the part is cooled to room temperature and the adhesive formed in step 35 is applied over the tungsten carbide layer (step 42). It may be necessary to use one or more coats of adhesive because some of it may be soaked up by the tungsten carbide particles.

At step 44, nickel chrome particles of 140-250 mesh are applied over the wet adhesive. The number of particles which adhere is determined by the amount of adhesive and the mesh size of nickel chrome as the major parameters. The smaller the mesh size, the more solid the coating, so that if a solid coating, free of voids and with filled interstices, is desired, a small mesh size is used. On the other hand, if it is desirable to leave voids and open interstices for lubrication or other operating functions, larger mesh sizes should be used.

The article is now oven dried (step 46) at temperatures of the order of 3500-4000F for the amount of time required to bring the piece up to a predetermined temperature which temperature is sustained until all the water is evaporated out of the adhesive.

Here, again, the drying is carried out in a conveyor type oven at a temperature of the order of 350 -400 F for a time which depends on the mass of the article. The cycle should be sufficient to insure that all water and moisture is evaporated from the part.

The part is cooled to room temperature (step 47). When cool it is inspected and any excess particles of tungsten carbide and/or adhesive on the surfaces may be removed with a knife or similar instrument.

Next (step 48) the coating is metallurgically fused to the blank by placing the article in a vacuum furnace, hydrogen atmosphere controlled furnace or in a salt bath furnace, with best results being produced in the vacuum furnace at a temperature of the order between 1925 and 2025"F. The part is held at that temperature for about 3 to 5 minutes to insure that the nickel chrome material reaches the liquidus state and the entrapped gas is evacuated so that the nickel chrome flows into the interstices between the tungsten carbide particles. If the furnace has a quench chamber, the parts go directly from the fusing step to quenching. If it does not, a separate quench bath is required. After quenching, the part is tempered to bring it to the desired hardness. After the part is tempered, the inside diameter of the piece is honed or ground (step 50) and lapped to the proper dimensions and smoothness. The particular technique used to finish the inside diameter (I.D.) of the piece accurately depends upon its size and shape.

The bushing (part or piece) is mounted on a mandrel and the outside diameter (O.D.) is ground to insure concentricity with the I.D. to within .0002" or less (step 51). Now, using the ground O.D. surface as a chucking surface, the ends and face of the piece are ground to the proper smoothness and dimensions (step 52).

FIGS. 2, o and 4 illustrate a machine for carrying out the coating portion of the method of the invention for producing articles having an outside diameter of one inch or less and an inside diameter not smaller than about .140 inch. The machine is designated by the numeral 60 and is seen to comprise a pedestal 62, a motor 64 which is mounted on the pedestal by means of a universal position ball mount 66 and a drive casing 68. The drive casing 68 contains a gear box and a worm drive for rotating a jig 70. Motor 64 is preferably a d-c gear motor with a foot controlled switch 65. The switch 65 controls the motor speed to permit the operator to vary the motor speed and the jig rotation speed during the coating process.

The jig 70 (FIG. 3) comprises an outer drive ring or worm gear 72 which is driven by a drive 74 so as to rotate a holder 76. The holder 76 is locked in position with respect to drive ring 72 by means of ball lock retainers 78. The bushing to be coated is placed in holder 76 and is held in position by means of one or more spring clips 80.

FIG. 4 illustrates the attitude of machine 60 for coating the inner surface of a bushing piece. The bushing is slipped into place and held by the spring dip 80 (FIG. 2). A brush 82 is used to apply the adhesive to the inner surface of the bushing while the holder is rotated. After the inner surface is coated with adhesive, while wet, tungsten carbide particles are poured from a container 84 into the bell of holder 76 as the holder is rotated. The particles which do not adhere to the piece drop into a recovery pan 86.

The piece is then removed from the holder and dried. The piece is reinserted in the holder and is again coated with adhesive and while still wet, nickel chrome or suitable alloy is poured from container 84 into the bell of holder 76. The excess falls into the recovery pan 86, (i.e. those particles which do not adhere to the wet adhesive). The part is then dried. Preferably, the d-c motor 64 is controlled by foot switch 65 to give the operator variable speed control, but any suitable control means may be used with the motor.

FIG. 5 illustrates a modified machine 90 for making articles having inside diameters of the order of about 3/4" to 6". This machine is actually larger than that of FIG.

4 but it is drawn to a smaller scale than is FIG. 4. Machine 90 comprises a d-c gear motor 92 which is a variable speed and is foot switch controlled by foot switch 93, which is similar to switch 65, a gear box 94 and a gear hub 96. The gear hub 96 supports and rotates a drive plate 98 inside of which there may be mounted a sleeve 100 which is of the proper size to hold a holder 102 in position. A clip 104 holds a bushing 106 in position. Operation is the same as has previously been described and the nonadhering matenal is recovered in a pan 108.

FIG. 6 is an enlarged view showing a portion of the inner surface of an article of the invention wherein several layers of a matrix 110 of tungsten carbide and nickel chrome have been fused to the body 112. For the purpose of illustration, the several layers of a matrix 110 are shown as particles, but during the furnace fusing step, the particles of nickel chrome pass into the liquidous state, and fill all the voids and interstices between the tungsten carbide particles, which retain their original shape and do not go into solution. The nickel chrome becomes solidified.

It is metal fusion bonded to the inner wall of the bushing, bonding the particles of tungsten carbide and since the adhesive is also a fluxing agent, it allows the surface of the tungsten carbide particles to be wetted and bonded to the nickel chrome. When the surface is finished along the line 114, it can be seen that the surface presents a substantially solid dense surface of tungsten carbide. By properly controlling the particle size of the tungsten carbide, up to 90% or more of the finished surface will be exposed solid tungsten carbide. This depends on the mesh or particle size used and the amount and type of finishing. Each exposed particle of tungsten carbide has an exposed surface of the proper diameter to thereby contribute to the total wear resistant surface. Such an article will possess a long life since the tungsten carbide used is a cast grade ranging up to 9.9 on the MOHR scale. On that scale the diamond is 10.0 and the normal sintered tungsten carbide bushing may only reach 9.3-9.4. Consequently, as long or longer life may be expected from bushings of the invention over those of the prior art. This is particularly true when the bushing is used in the processing of abrasive material.

FIG. 7 is a view similar to that of FIG. 6 and shows a body 116 to which an essentially single layer of tungsten carbide particles having their regular blocky shape have been applied and to which has been applied a controlled layer of nickel chrome matrix material. The nickel chrome reaches the liquidous state in the presence of the fluxing agent in the adhesive and the particles of tungsten carbide are wetted with nickel chrome during the furnace fusing step. The excess nickel chrome clings to the wall and gathers in fillets 119 of nickel chrome at the base of each particle of tungsten carbide 118. This provides great mechanical strength against tool pressures and forces.

Heat treating follows the fusing stage. When the surface is finished along line 1 0, which is part of the parent material of the hardened drill bushing body 134 in order to protect the tool cutting edge from damage as it first enters the bushing. Such damage might occur if it were to contact a radial tungsten carbide surface with its cutting edge as shown in the bell mouths of FIGS. 8, 9 and 17. This is particularly true if the tool enters the entry hole 135 off center due to a tool running out of round or oscillating until controlled by the inside diameter of the bushing. It should be noted that run out or some oscillation is not unusual in long tools.

FIG. 11 is a view similar to that of FIG. 9 of a non-headed bushing which comprises a body 140 to the inner surface of which there is applied a matrix 142 of nickel chrome throughout which are distributed articles of tungsten carbide. A shoulder 141 limits the application of the matrix 142 to the area shown in the figure. The bell mouth or entrance 143 for the tool or drill is formed of the parent material of the hardened bushing body and is not covered by the matrix so that the tool is protected from damage as it first enters the bushing. This is particularly true if the tool enters off center due to its running out of round or oscillating until its movement is controlled by the inside diameter of the bushing. It is thus seen that the bushings of FIGS. 10 and 11 are for the same general purpose.

FIG. 12 is a view of a pump bearing wherein the inner surface of the body portion 144 and the outer surface of the head 146 are covered with a matrix 148 of nickel chrome throughout which are dispersed micron size particles of tungsten carbide with a thickness in the order of .003"-.005".

Such bearings may also be made with the matrix just covering the outer surfaces of the head 146.

FIG. 13 is a block diagram of the method of the invention used in the production of small bushings having inside diameters of the order of between .005" and .140".

The blank is machined on conventional machine tools. Before proceeding with the coating process, the part must be chemically clean and free of any dirt, oil, etc. (step 150). The preferable method is to batch clean the bushings metallurgically in a hydrogen atmosphere controlled furnace. A blind hole is drilled in the blank (step 151).

Tungsten carbide particles of the proper mesh size are precoated (step 157) with the adhesive formed in step 155. The adhesive mixture used in step 157 is thin and freeflowing so that there is a low concentration of nickel chrome in suspension. Preferably, the adhesive is poured into a container of the tungsten carbide particles and the combination is thoroughly mixed. The mixture is placed in, for example, a variable speed centrifuge to remove the excess liquid. The wetted mixture is placed in a mixer where it is agitated in the presence of a hot air stream.

This is done to dry both the adhesive coating and its nickel chrome powder on the individual tungsten carbide particles and to separate the particles.

Before the mixture is completely dried, the particles are lightly sprayed or dusted with a dry fog of nickel chrome powder which will adhere to the wet adhesive. This insures that there will be an adequate supply of nickel chrome to form fillets between the points of contact of the tungsten carbide particles and the body of the bushing. A greater quantity of precoated particles may be produced than is needed as the excess, after it is completely dry, may be stored in sealed containers for future use.

Now, boric acid dissolved in distilled water (step 152) and nickel chrome micron size powder (step 154) are added together to form an adhesive 155 having a consistency of heavy oil which can be varied in its consistency by using more or less nickel chrome powder. This can be accurately measured and reproduced by using predetermined ratios for fluid measure (step 152) to weight of nickel chrome (step 154) to insure repetitive consistency and the correct amount of nickel chrome in suspension in the adhesive. Now, (step 156) adhesive is applied to the inner surface of the longitudinal blind axial opening in the bushing. Next (step 158) the dry, precoated tungsten carbide particles of a predetermined mesh are placed in the longitudinal blind axial hole which had been drilled in the blank to a level which will assure an excess when the top is cut off in subsequent operations. Now the articles are dried (step 160) by being placed in a conveyor type oven at about SOC to 4000F. The part remains in the oven until it reaches the established temperature and all moisture or water is evaporated out of the adhesive. The part is then allowed to cool at room temperature. Now, (step 161) adhesive is applied to the exposed projecting tungsten carbide particles and into the cavity formed by the coffer dam. Next, (step 162) a measured amount of nickel chrome is added to the top of the piece partially filling the coffer dam, and a few drops of adhesive are added into the small mass of nickel chrome powder in order to saturate the nickel chrome. There must be a sufficient amount of nickel chrome to insure that all the interstices between the tungsten carbide particles are filled with nickel chrome. The bushing is now dried (step 163) by being placed in a conveyor type oven at about 350C to 4000F until the part reaches that temperature at which all moisture or water is evaporated out of the adhesive. The part is then allowed to cool at room temperature (step 164). Now, (step 165) the bushing is placed in a vacuum furnace, hydrogen atmosphere controlled furnace or salt bath furnace at a temperature of the order of 1925 to 2025"F until the part has reached the desired temperature and is held at that point for 3 to 5 minutes. As the furnace is cooled down, the parts are removed at proper temperature for heat treating, quenched in the proper medium and then put through an annealing stage for the proper steel bushing hardness. This completes step 165. If a vacuum furnace is used, it is possible to move the bushing directly into a heat treating stage for quenching followed by annealing. At step 166 the top and bottom of the piece are ground off which removes the coffer profile as well. Now, the outside diameter is ground to the desired size and smoothness (step 168) and a hole of the desired size is pierced in the fused matrix (step 170). This pierced step may be carried out by either electrode discharge mach- inging, electro chemical piercing, or in the case of very small holes, a laser beam can be used. Finally, the piece is honed and lapped to a final finished inside diameter and surface finish (step 172).

FIGS. 14-17 illustrate some of the steps used to produce a bushing of the configuration shown in FIG. 8, having an inside diameter between .0135D and .140" and an outside diameter between .250" and .500".

In FIG. 14, the illustration shows a piece 180 into the top of which a coffer dam 182 has been machined during the process described in connection with FIG. 13 (step 150). Following the steps depicted in FIG.

13, the adhesive which is produced by mixing 152 and 154 of FIG. 13 is in step 156 applied to the wall of the longitudinal blind axial hole 181 in piece 180 of FIG. 14. Then (in step 158) this hole is filled with precoated particles 184 as illustrated in FIG. 14 and is dried in an oven as has been described (step 160). FIG. 15, shows the manner in which, after fusion, the small mound of nickel chrome has, in the liquidus state, seeped down between the particles of tungsten carbide filling all crevices and interstices between the particles to form a solid plug of tungsten carbide in a matrix of nickel chrome. The plug is of a predetermined diameter which will leave a wall thickness of about .003" to .005" after finishing. After cooling (step 164) and tempering (step 165) the top 185 and bottom 186 are ground off in step 166 (FIG. 16). The outside diameter is centerless ground (step 168) and then the hole is pierced using electro discharge machining, electro chemical machining or laser beam to pierce a hole 187 (step 170).

Next, final honing and lapping is done to the proper diameter (step 17 ). FIG. 17 shows the finished bushing formed by means of electro discharge machining, electro chemical machining or a similar method as may be required. The electrode for an electro discharge machine is shown at 188 and the finished hole designated 187 is seen to have a suitable coating 189.

HG. 18 illustrates a step in the method of producing very small bushings having inside diameters of the order from .005" to .140" and outside diameters of the order from .250" to A37". The opening 190 which is a square bottom longitudinal blind axial opening is coated with adhesive which is also a fluxing agent derived from mixing (step 152) and (step 154). The opening is then filled with particles of tungsten carbide of a predetermined mesh which have been precoated with a dry coating of adhesive. This is equivalent to step 158 in FIG. 13. The piece is now dried as in step 160 of FIG. 13. The top cavity formed by coffer dam 192 has adhesive applied including the inside cavity formed by the coffer dam which is equivalent to step 161 and now, in the next step which is equivalent to step 162 of FIG. 13 particles of nickel chrome powder are placed in the coffer dam cavity while the adhesive is still wet with additional drops of adhesive added and the measured quantity of nickel chrome to insure that there is sufficient reservoir of metal during fusing (step 164 of FIG. 13) so that all cavities and interstices between the particles of tungsten carbide are filled to form a solid plug of tungsten carbide in a nickel chrome matrix. Prior to fusing (step 165) a drying stage must be completed which is equivalent to step 163 in Figure 13. The piece may be taken out of the furnace at the proper temperature and quenched for hardening and then followed by annealing. Now, in step 166 of Figure 13, any suitable method may be used to remove the top along line 194. At the same time the opposite end is sized to obtain the proper overall length of the bushing. In the next step, equivalent to step 168 of Figure 13, the outside diameter is finished to its final outside diameter and surface finish. Next, the longitudinal axial opening is pierced through as described in connection with step 170 of Figure 13, using electro-discharge machining, electro-chemical machining, or a laser beam, for a very small hole. This piercing may be done for improved concentricity while the piece is rotated, but stationary mounting also can be used. Now the pierced longitudinal opening 196 in Figure 19 may be honed and lapped to its final diameter and surface finish. Any deburring, etc., part marking and other aids for the user are carried out at this last stage.

It is to be understood that no claim is made herein to what is claimed in claims ' 3, 4 and 8 of Specification No. 6859/78 (No.

1 602 785).

Subject to the foregoing disclaimer

Claims (18)

WHAT I CLAIM IS:

1. A method of manufacturing an article for accurately confining a cylindrical element rotating about its longitudinal axis which comprises; forming from steel a blank or body having the desired outer and inner configurations and a central longitudinal axis; cleaning the blank so that it is free of contaminants; forming an adhesive of boric acid dissolved in distilled water and powder of a first material having a hardness in the range of from 59 to 67 Rockwell C; applying the wet adhesive to the inner surface of the blank; adding particles of a second material having a hardness in the range of from 84 to 93 Rockwell C to the wet adhesive so that the wetted surface captures the second material particles; drying the blank at a temperature in the range of from 350" to 400 F for a time sufficient to remove the water and moisture from the blank; adding further wet adhesive to the coated inner surface of the blank; adding powder of the first material to the wet adhesive on the coated inner surface so that the wetted surface captures the first material power; drying the blank at a temperature in the range of from 350" to 400"F for a time sufficient to remove the water and moisture from the blank; raising the temperature of the blank to a temperature in the range of from 1925 to 2025"F and holding the blank at the temperature in the range of from 1925 to 2025"F for a period in the range of from 3 to 5 minutes; tempering the blank for a time and at a temperature appropriate for treating the body of the blank; and finishing the blank to the desired size and smoothness.

2. A method of manufacturing an article for accurately confining a cylindrical element rotating about its longitudinal axis, which comprises; forming a blank having the desired outer configuration; cleaning the blank so that it is free of contaminants; drilling a blind longitudinal opening in the blank; forming an adhesive of boric acid dissolved in distilled water and powder of a first material having a hardness in the range of from 59 to 67 Rockwell C applying the adhesive to the surface of the longitudinal opening; precoating particles of a second material having a hardness in the range of from 84 to 93 Rockwell C with the adhesive; filling the longitudinal opening with the precoated particles of the second material; drying the blank at a temperature in the range of from 350" to 4000F for a time sufficent to remove the water and moisture from the blank; adding adhesive to the longitudinal opening; adding a measured amount of particles of the first material at the top of the longitudinal opening; drying the blank at a temperature in the range of from 350" to 400"F for a time sufficient to remove the water and moisture from the blank; raising the temperature of the blank to a temperature in the range of from 19250 to 20250F and holding the blank at the temperature for a period of time in the range of from 3 to 5 minutes; tempering the blank for a time and at a temperature appropriate for treating the body of the blank; removing the top and bottom of the blank to thereby expose the ends of the filled longitudinal opening; piercing an opening through the filling longitudinal opening; finishing the blank to the desired size and smoothness.

3. A method according to claim 1 or claim 2, wherein the first material is nickel chrome and the second material is tungsten carbide.

4, A method according to claim 2, wherein the step of piercing the opening is carried out by electro-piercing.

5. A method according to claim 2, wherein the step of piercing the opening is carried out by electro-discharging.

6. A method according to claim 2, wherein the step of piercing the opening is carried out by a laser beam.

7. An article of manufacture for accurately confining a cylindrical element rotating about its longitudinal axis produced by the method of claim 1 or claim 2, comprising; a body formed of steel and having a longitudinal opening therein; a liner of particles having a hardness in the range of from 84 to 93 Rockwell C in a matrix of material having a hardness in the range of from 59 to 67 Rockwell C bonded to at least a portion of the longitudinal opening in the body and having an opening therein to receive the cylindrical element and to permit said cylindrical element to rotate freely therein; the dimensions and material of the liner being such that the liner and the body together have a coefficient of thermal expansion substantially equal to that of the cylindrical element thereby to accurately maintain the position of the cylindrical element as it rotates and confine it to rotation about its longitudinal axis.

8. An article according to claim 7, wherein the particles of material having a hardness in the range of from 84 to 93 Rockwell C are tungsten carbide.

9. An article according to claim 7 or claim 8, wherein the matrix of material having a hardness in the range of from 59 to 67 Rockwell C is nickel chrome.

10. An article according to any one of claims 7 to 9, wherein the longitudinal opening is a cylinder and is provided with an outwardly flared portion at one end thereof.

11. An article according to claim 10, wherein the longitudinal opening is a right circular cylinder.

12. An article according to claim 10, wherein the end portion of the body con taining the outward flare is of a larger diameter than the balance of the body.

13. An article according to claim 10 or claim 12, wherein the liner is applied to the outwardly flared portion.

14. An article according to any one of claims 10 to 13, wherein the liner comprises a plurality of layers of tungsten carbide particles.

15. An article according to any one of claims 10 to 13, wherein the liner comprises a single layer of tungsten carbide particles.

16. An article according to claim 8 or claim 9, wherein the liner comprises a plurality of layers of tungsten carbide particles.

17. An article according to claim 8 or claim 9, wherein the liner comprises a single layer of tungsten carbide particles.

18. An article according to claim 7, substantially as hereinbefore described, with reference to Figures 1 to 5, Figure 6, Figure 7, Figure 8, Figure 9, Figure 10, Figure 11, Figure 12 or Figures 13 to 19 of the accompanying drawings.