US2225193A - Abrasive wheel - Google Patents

Description

Dec. 17, 1940- R. c. BENNER ETAL ABRASIVE WHEEL s Sheets-Sheet 1 Y Filed Sept. 15, 1937 INVENTOR. RAY OND C. BENNER WILLXAM M/ JG. SOLEY MM ATTORNEY.

Dec. 17, 1940. R. c. BENNER ETAL 2,225,193

ABRAS IVE WHEEL Filed Sept. 15, 1937 3 Sheets-Sheet 2 IN VENTOR.

RAYMOND C, ENNER wn L|AM G s EY ATTORNEY.

R. c. BENNER ETAL 2, 9

' ABRASIVE WHEEL Filed Sept. 15, 1957 3 Sheets-Sheet 3 INVENTOR. RAYMOND c BENNER WlLLlAM G: SOLEY BY ATTORNEY:

Patented Dec. 17, 1940 UNITED STATES 2,225,193 ABRASIVE! WHEEL Raymond C. Benner and William G. Soley,

Niagara Falls, N. Y., assignors to TheCarborundum Company, Niagara Falls, N. Y., a cor-.

poration of Delaware Application September 15, 1931, Serial No. 164,028

8 Claims.

This invention pertains especially to articles in which the active abrasive element is bonded to" form aggregates or' inserts which are distributed ina matrix material to form abrasive products of improved cutting characteristics.

Heretofore, in the making of grinding wheels in which diamonds are used as the abrasive, the bonding-of the diamonds has been mostly confined to such plastic materials as synthetic resins and sintered metals which can be consolidated into a dense and practically non-porous mass. Dimculty hasbeen experienced in the usual ceramic bonding of diamond abrasive wheels in that there is a break-down of the bond during cutting. This sort of break-down is very desirable with cheap abrasives, such for example, as 'silicon carbide or fused alumina, etc., but

' such a break-down of the bond when diamonds are used as the abrasive is not desirable. 'This is due to'the fact thatin order to be practical in operation and to secure suificient service to warrant the cost, the diamonds'must be retained in the cutting surface of the wheel over a long period of time.

The present invention relates to the making oi abrasive grinding wheels or discs using diamonds, or other of the more costly grinding media wherein the abrasive particles are incorporated in bonded aggregates or inserts. These inserts or aggregates are. then positioned or distributed in and bonded with a matrix of supporting material to form the working surface or edge of the final grinding wheel or 'disc. The material used for bonding these inserts may be any type of bond such as'ceramic, metallic, rubber, or resinous in character. The supporting matrix material is usually, although not necessarily so, a bond of different characteristics than the bond for the-insert, and depends.upon the type of wheel being made and the use towhich it is tobe put. This use of a matrix material differentin characteristics from the bond used in the insert gives the resulting wheel cutting properties which are distinct from standard wheels of uniform surface and constitute an improvement in cutting rates and efficiency ratios over such wheels.

The properties of different wheels can be altered' to adapt the wheel to various applications by matrix material may be any one of a number of substances, including rubber, ceramic, resinous or metallic compositions, etc.

One of the principal objects of the present invention .is to provide ways for the more economic use-of diamonds in the making of grinding wheels having,- improvedcutting rates and emciencies. It is the purpose to attain these improved properties while actually using less diamonds than have hitherto been used for making wheelsof similar size.

Another object of the present invention is the proposed use bf diamonds in larger wheels than have heretofore been made with diamonds, such wheels to possess diamond-grinding surfaces greater and more extensive than have been previously considered feasible.

A further objectis the provision of diamond wheels of increased thickness presenting wide peripheral grinding surfaces without excessive use of diamonds. One of the proposed methods of accomplishing this is by use of thin overlapping annular segments embedded in the wheel p p e Another object is the production of diamond grinding wheels capable of a vast range of cutting characteristics each adaptable to a specific type of work, this to be accomplished by careful selection of insert-bond and matrix and proper use, of one with the other.-

Other objects and advantages'of the invention will become apparent during the course of the following description. The nature of the present invention is better illustrated by the following drawings in which embodimentsofthe invention are shown:

Figure 1 is a plan view of a disc wheel showing the bonded inserts or discs arranged in the cutting surface of the wheel Figure 2 is a cross section on the line 11-11 of Figure 1.

Figure 3 is a plan view of a cut-oil wheel.

using alternately spaced diamond bonded inserts in both sides of the wheel.

Figure 4 is a cross section along the line IV-IV ofFigure3. I

Figures 5 and.6 are plan views of 'further modifications of wheels containing bonded abrasive I inserts.

Figures '1 and 8 are cross sections along the lines VII-VII and VIII-VIII of Figures 5 and 6, respectively.

Figure 9 is a plan view of a cut-off wheel showing a modification of the positioning of the inserts.

Figure 14 is a plan view of a large size diamond wheel using overlapping inserts to present a large broad side grinding surface.

In all of the drawings like numerals refer to the same thing throughout the figures. Numeral I is the bonded insert or aggregate which contains the diamond abrasive particles, and 2 is the matrix material or secondary bond in which the abrasive inserts I are embedded. 3 is the backing or support used in some types of wheels to which the shaped matrix 2 is cemented or fastened and serves as a means for fastening to the grinding apparatus by means of bolts through holes 4.

In Figures 1 and 2 the inserts I are shown as ceramic bonded diamond particles while the matrix 2 is a metallic material. The backing is made up of a resinous material such as Bakelite or other thermo-setting resin.

Figures 3 and 4 show a modification of a cutoff wheel using inserts according to the present invention. The inserts I in this example are metal-bonded diamond particles and the remainder of the wheel body is made up of a resin bondmatrix material 2 may be dressed down between L the diamond-containing Inserts 2 after periods of use without any great inconvenience. The

inserts are shown here of resin bonded diamonds.

. and the matrix of rubber bonded abrasive such as silicon carbide or fused alumina.

Figures 6 and 8 illustrate a modification of the type of wheel shownin Figures 1 and 2, using a different shaped insert I, and like the wheel in Figures 5 and 7 may be easily dressed down. In this modification the inserts are shown of a metal bonded abrasive with the matrix material 2 also composed of a metallic composition.

Figure 9 is a plan view showing a still further modification of a wheel in which the inserts I are positioned in more or less spiral form.

Figures 10 and 11 illustrate a wheel having wedge shaped metal bonded inserts I- positioned in the face of a rubber matrix 2.

Figures 12 and 13 are side and front plan views respectively of a grinding wheel in which th periphery or edge of the wheel constitutes the grinding surface and whose edge is.oi" considerable thickness in order to present a broad working surface. The diamond-containing inserts I are in the form of thin annular segments having an outside curvature corresponding to the outside circumference of the completed wheel and are embedded in the matrix material 2 to form part segments for use in wheels as shown in Figures 12 and 13 is to mold and press complete thin rings of the composition of the inserts and having the same outer circumference as that of the final grinding wheel desired and slightly over half the thickness of the wheel in which they are to be incorporated. After final firing or curing these complete annular rings are broken or cut into segments of the length desired for embedding I in the surface of the wheel.

In Figure 14, the inserts I of ceramic bonded diamonds are overlapping and embedded in the rubber matrix 2 to form a large broad top dressing surface of considerable area.

According to one method of making up wheels containing bonded diamond inserts, the inserts are pressed to shape and cured or fired before incorporation in the wheel. However, these inserts, if of approximately the same maturing temperature as the matrix material. may be made up at the same time the matrix material is mived and simultaneously pressed and fired with it by the use of dividing partitions in the mold, without departing from the scope of this invention. For example, if a wheel similar to that illustrated in Figures 6 and 8 is to be made up and the materials of the matrix and abrasive inserts have approximately the same maturing temperatures then both mixes may be made in separate batches at the same time and in setting up the mold, partitions may be temporarily placed in the mold and the two different mixes placed in their respective positions, the parti-' tions carefully withdrawn and the whole wheel pressed in a single operation and later fired.

Where the inserts are formed prior to incorporation in the matrix of the wheel the following method may beused to properly position the inserts in the finished wheel, although this is not the only method which may be used within thescope of my broad invention. A piece of paper or other material carrying the desired design is placed on the bottom of the mold. This paper has on it a design showing the desired location of the inserts which are then positioned accurately according to the design on this base paper. The inserts may be held in position in contact with the paper by the presence on the paper of a small amount of transparent adhesive such as glue or resinjust suflicient to hold the insert firmly while the loose-matrlxmaterial is pouredinto the, mold and leveled off, after which the wheel is pressed and fired or cured. This method is especially desirable where inserts are intricately positioned, such as for example those shown in Figure 9. Careful positioning of the inserts not only improves the appearance ofthe wheel but keeps it in better balance and helps to insure utilization of the abrasive in the desired manner. Where positioning on opposite sides of the wheelis desired, as in. Figures 3 and 4, it is most readily accomplished on the second side by use of a. perforated template.

i As a specific example of making ceramic bonded diamond inserts abrasive particles are mixed with the bond in the following proportions and'pressed at approximately 8000 lbs/sq. in. and after drying are fired at 1300 C.

These inserts are held together by a temporary binder which is burned out by firing up to 500 C.

in an oxidizing atmosphere, after which they are fired under reducing conditions to 1300 C.

The ceramic bond used in the above two mixes is exemplified by the following two bonds, al-

though many other ceramic compositions may be used which would work satisfactorily.

The following mix is an example of one which, has been found very satisfactory in making metal bonded diamond inserts. I

Per cent Bond (20% tin-80% copper) 80 80-140- grit diamonds 10 180 grit silicon carbide- 10 After thorough mixing of the ingredients the mix is screened through a 60 mesh screen to prevent balling up of the metal bond and then pressed at l0,000-l00,000 lbs/sq. in;, after which they are burned at 700-750 C. under an atmosphere of illuminating gas. pellets are placed between bats and weighted downwith a weight of a few pounds on the upper bat to prevent warping. After cooling they are removed and cleaned oil with a wire brush and, washed with a 5% solution of sodium cyanide.

After the diamond inserts have been made and properly burned or matured, they are positioned in a ring mold and-the matrix or supporting mix filled in around the inserts, leveled off, and pressed at 10,000-75,000 lbs/sq. in. The wheel is then removed from the ring mold and burned in a furnace between bats to prevent warping. The following two mixes are given as highly. satisfactory examples of metal bonds which may be used as the matrix material and are fired using the same temperatureand atmosphere as the metallic inserts given above.

Per cent Copper 88 Tin 12 Per cent Copper r 92 Tin 8 v I Instead of using.ceramiccompositions or metallic bonds for either the inserts or matrix of the wheel as shown-above, either the matrix or infor use as a rubber matrix material:

During firing'theinserts' or that temperature for 2 hours.

. illustrated reference was serts may be made up using a rubber bond. Although smoked sheet rubber is given below in the specific example, a. mix may be made up using either dispersed or decomposed rubber with 80-140 grit diamonds 42.5

400 grit alu 42.5

Inserts of the above ingredients are pressed and partially cured for 5 minutes at 120 lbs. steam pressure after which they may be removed, placed in a ring mold, rubber matrix material as specified below added, and the inserts and matrix combined given a further press cure for minutes at 120 lbs. steam pressure. Instead of ouring in the press the matrix and insert after short pressing may be oven cured 4 hoursat 300 F. It should be understood that rubber bonded inserts may be used with other matrix material such as resins, in which event the inserts maybe completely cured before incorporation in the matrix.

The followingcomposition is a typical mix Parts Smoked sheet rubber a 100 Sulphur 50 Accelerator Zinc nxirln In making inserts of a=resin bonded abrasive I have found that phenol-formaldehyde resins are highly satisfactory. As an example of a resinous I insert composition-the following has worked out well:, a

I Per cent Powdered reactive phenolic resin 20 80-440 grit diamonds 40 400 grit alumina 20 100 and finer alumina 20- In making inserts of the above mix the abrasive is first mixed thoroughly and moistened with fu'rfural, after which the powdered resin is added to give a free-flowing mix. This mix is cold pressedand the inserts as made are bakedin an oven by bringing them slowly up to 350 F. over a period of 24 hours and holding at that temperature for 2 hours and then cooling.

The following is a specific example of a resin mix which has been found adaptable for a. matrix material for bonding abrasive inserts. In forming the matrix shapes of such a resinous compound the inserts are placed in the mold, the powdered mix filled about the inserts, hot pressed 30 minutes at 140 lbs. steam pressure, cooled under pressure, removed from the mold and baked in an oven by taking them slowing up to 350F. over a period of '24 hours and holding at Phenol-formaldehyde Flint filler- In thespecific embodiments of wheels herein made to, the desirability in certain cases of dressing down the wheel after periods of use. This is especially applicable to wheels in which the diamonds are. embedded in inserts or aggregates in which the. bond of the molding power 20 Per cent insert is ofa porous, brittle type to produce a free, rapid cutting action. This bond, if used alone wears away so rapidly as to cause an undesirable high wheel loss, but when used together with a matrix of tougher material this wheel loss is reduced by protection of the more fragile insert-bond by the tougher matrix comosition. To explain more fully, when the wheel is first put in use the surface of the insert is approximately flush with the surface of the matrix, but the bond of the insert quickly wears away to a slight extent exposing a number of diamond cutting surfaces which protrude above the bond. However, the tougher matrix material does not wear away as rapidly'and supports the work sufliciently to prevent further immediate wearing away of the insert-bond and ripping out of the diamond particles, although undergoing wear sufiiciently to permit the partly.exposed diamond particles to cut freely. At the same time this slightly lowered bond surface of the insert allows for a chip clearance not otherwise present and an opportunity for the detritus to be easily carried away. After the abrasive insert has worn down so far as -to materially diminish or retard the cutting action it becomes desirable to cut or dress down the matrix slightly. For this urpose it is advantageous to be able to apply a dressing tool which can cut back the matrix without also striking the abrasive insert. This is most readily accomplished where the configuration of the inserts is as shown in Figure 6 for example where the dressing is done in two steps, first the central portion and then the spokes between the inserts.

By the used bonded inserts in making diamond grinding wheels many advantages are obtained. For example, in the pressing of diamond wheels it is quite essential for the best results that the wheels be pressed at relatively high .these high pressures can pressures, and when the whole wheel is madeup' as hitherto carried out, large massive presses and expensive pressing equipment is necessary to form the wheel. By the proposed method of using inserts of comparatively small area; individually with respect to the entire wheel area, be reached with the far less costly pressing apparatus. In the case of small buttons or pellet shaped inserts, pressures in the neighborhood of several-thousand pounds per square inch may be had by ordinary hand pressure apparatus. This ability to obtain highlycompressed bonded diamond segments or inserts without elaborate pressing equipment constitutes a marked economic saving.

A further saving is realized by the fact that instead of.diamonds being used throughoutthe entire wheel, only a portion of the wheel abrading surface contains diamonds. Not only are less diamonds used, but this accomplished while at the same time wheels are made having a free cutting action without an extravagant wheel loss.

Grinding wheels or disks made up according to the present invention having diamond particles present only in inserts placed in the abrading surface of the wheel instead of being incorporated in the entire grinding surface not only do not suffer any loss in cutting rate or efliciency in comparison with a wheel having diamonds in the entire working face, but in fact, show a definite increase in the cutting rate and an improvement in the efliciency over such diamond cutting wheels. Wheels using considerably less of diamond particles but made up with spaced inserts or aggregates-show a higher efficiency and cutting rate than similar bonded wheels using a greater amount of diamonds spread throughout the cutting surface. This is accomplished without any detrimental effect upon cutting characteristics.

By the use of a free-cutting bond for the inserts which is backed up or supported by a tougher matrix material the cutting properties such as cutting rate and efficiency ratio of the wheel is improved by the use of inserts in place of the standard uniform grinding surface as commonly used regardless of the purpose or application to which the wheel is put. By efliciency ratio we mean the resulting figure obtained by dividing the grams of material being ground which is removed per minute by the grams of wheel loss per minute. A preferred wheel is one which shows a high efliciency ratio. 'Wheels made with inserts have exhibited extremely high eiiiciency ratios as well as greatly improved cutting" rates over standard wheels regardless of the work or purpose of the wheel.

Some explanation has been suggested above as to the reason for this improved cutting action and efliciency. It has, generally speaking, been found advantageous to use an insert bond which possesses the property of breaking away freely around each diamond particle and exhibiting some signs of brittleness, although having surficient tenacity to keep the diamond particles from ripping out. The most desirable bond to be used varies, dependent upon the material being ground and other factors just as in the case of ordinary grinding wheels. On the other hand, the bond for the matrix or remainder of the surface of the wheel is chosen usually so that it possesses greater toughness and strength than the insert bond, has an improved abrading or wear resistance, and acts as a support to prevent undue break-down of the more fragile insert material. In general rubber matrices are indicated where some degree of resilience is desired, resin matrices where a stiff somewhat brittle action is desired, and metal matrices for use on hard materials such as ceramic products under certain circumstances.

In the use of diamonds as a grinding medium in wheels it has been found extremely diflicult to find a bond which satisfactorily wet the diamond surfaces so as to tenaciouslyhold the diamonds in place and give a desirable cutting action and also possessed the toughness and resilienoe necessary to be used to make up the entire body of a wheel of any considerable size. This, in addition to the excessive cost entailed in using diamonds promiscuously throughout the wheel, has limited the use of diamonds to wheels of smaller size. By the proposed use of inserts, a wheel body may be used which possesses properties suitable for forming larger wheels without regard to its ability to tightly bond diamonds and a different bond especially adapted for bonding diamonds-than used for the inserts. .This use of a matrix or body different in properties from the insert bond thus aids in the production of wheels of increased cutting rate and efficiency in addition to the economic reason of saving on the amount of diamonds necessary. Then too by the correct choice and combination of insert bond and matrix bond any desirable cutting action may be obtained overa substantial range of dif ferentiations.

While severalspecific examples' and mixes have been herein given to show the actual working of this invention, we do not wish to be limited to these embodiments solely as illustrated. We

we wish it understood that other costly abrasives such as boron carbide and the like may be used without departing from the spirit of the present invention.

We claim:

1. As an article of manufacture, an abrasive article comprising ceramic-bonded diamond containing inserts embedded in a rigid, non-abrasive supporting matrix the surface of which is substantially flush with the grinding surface of the adjoining inserts.

2. As an article of manufacture, an abrasivetaining inserts circumferentially spaced about the. periphery of the wheel and embedded in a rigid,

non-abrasive supporting matrix forming the body of said wheel said matrix having greater wearresistance than bond of said inserts.

5. As an article of manufacture, an abrasive wheel comprising ceramic-bonded diamond-containing inserts circumferentially spaced about 5 the periphery of the wheel and embedded in a rigid, non-abrasive supporting matrix forming the body portions of said wheel said matrix having greater wear-resistance than bond of said inserts, and said inserts being so .shaped and positioned as to permit dressing of the body of the wheel after periods of use.

6. As an article of manufacture,*an abrasive article comprising ceramic-bonded diamond-containing inserts, embedded in a rigid, non-abrasive. body portion, said bodyportion having greater wear-resistance than the bond of said inserts.

7. As an article of manufacture an abrasive article comprising diamond-containing inserts bonded within by a bond having the free-cutting, friable characteristics of a ceramic bond, said inserts being embedded in a rigid supporting matrix of'non-abrasive material, the surface of which is substantially flush with the grinding surface of the adjoining inserts.

8. As an article of manufacture an abrasive article comprising ceramic-bonded diamond-containing inserts imbedded in a rigid non-abrasive organic supporting matrix, the surface of which issubstantially flush with the grinding surface of the adjoining inserts.

' RAYMOND C. BEITNER.

WILLIAM G. SOLEY.

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