US2418883A

US2418883A - Anchoring means for abrasive disks

Info

Publication number: US2418883A
Application number: US586929A
Authority: US
Inventors: Roger H Homeyer
Original assignee: Carborundum Co
Current assignee: Unifrax 1 LLC
Priority date: 1945-04-06
Filing date: 1945-04-06
Publication date: 1947-04-15
Anticipated expiration: 1964-04-15

Description

April 15, 1947. R, HOMEYER I 2,418,883

ANCHORING MEANS FOR ABRASIVE DISKS Filed April 6, 1945 IN VEN TOR.

{P0652 HOMYE Patented Apr. 15 1947 Niri-:o srr ANCHORING MEAN S FOR ABRASIVE DISKS Application April 6, 1945, Serial No. 586,929

This invention relates to the manufacture of abrasive articles. More particularly it relates to bonded abrasive articles such as grinding wheels or discs of the type which are secured at the flat side surface of the article to a suitable mounting plate or frame for support and/or reinforcement during use. The invention is especially concerned with the anchoring means provided in such abrasive articles for mounting them on their supports; it also pertains to methods of making wheels or discs of the described type which, when warpage or distortionof the abrasive body takes place during the process of making, and especially during the firing or curing of the article to its matured condition, will permit the mounting face of the wheel to be facilely dressed to an acceptacle flatness within the tolerance necessary to provide a strong and firm attachment of the wheel or disc to its supporting plate or frame with the anchoring means firmly and strongly retained in position.

According to the present invention, a bonded abrasive wheel or disc adapted for mounting on a flat side face thereof is provided with anchoring means embedded in' the bonded abrasive body and substantially flush with the mounting face of the article. The anchoring means consists of a strong and tough metallic insert, such as a threaded steel nut, and a relatively thin washer of softer material, the latter being located between the metal insert and mounting surface. The material of the washer is such that, if it is found necessary due to warpage during fabrication to lap or otherwise dress the mounting surface of the abrasive article to provide a suitably fiat face for mounting, the washer will be Worn down evenly with the surrounding bonded abrasive body and will not become separated from the contacting abrasive body by voids or cracks.

In order that the invention will be more clear- 1 1y understood and for illustrative purposes, reference is made to the accompanying drawings, in which: v

Figure 1 is a rear plan view of a grinding disc embodying the present invention, and showing the mounting plate partially broken away;

Figure 2 is a vertical cross-sectional view through the line 2-2 of Figure 1;

Figure 3 is a vertical cross-sectional view through an anchoring means of the type embodied in' the disc shown in Figures 1 and 2 together with that portion or the abrasive body surrounding the anchoring means, and depicts in exaggerated form the manner in which a part of the anchoring assembly during dressing is 4 Claims. (Cl. 51209) worn down even with the surrounding bonded abrasive body to provide a flat external surface.

Referring further to the drawings, Figures 1 and 2 depict an abrasive grinding disc adapted for side grinding and made in accordance with the teachings of the present invention. The abrasive disc illustrated in Figures 1 and 2 consists of an annular bonded abrasive body 4 having a flat side grinding face 5 and an opposite fiat supporting face ti. The bonded abrasive body may be any desired dimension, the diameter of such articles differing over a wide range of sizes; wheels or discs of the described type are usually several inches thick so as to provide an article of relatively long useful life. The bonded abrasive body 4 is composed of abrasive grain such as crystalline aluminum oxide, silicon carbide, or other granular abrasive material of the desired grid size or sizes, suitably bonded. The bond may be a vitrified ceramic material, or it may be a silicate, or a resin, or a natural or synthetic rubber compound.

As a support or means for mounting upon a grinding machine the abrasive body 4 provided with a steel or other strong rigid backing plate 7 attached to the flat face 6 of the abrasive body i by means of anchoring bolts Which are screwed into anchoring means 8. The backing plate I is provided with a central arbor hole 9 and three bolt holes I?) for fastening the backed disc to a mounting plate on the grinding machine. (The corresponding mounting plate for the grinding machine is not shown.) Although the abrasive disc as shown in Figures 1 and 2 is presented as attached to its mounting'plate, it is customary for the bonded abrasive body to be fabricated bythe manufacturer and supplied to the user who attaches the mounting plate I at the time and place of use. The mounting plate 5 is attached to the bonded abrasive body by means of anchor bolts I 3 which screw into and engage the threaded metal inserts II of the anchoring means 8. Alternatively a stud may be screwed into the insert II and a nut placed on the outer end of the stud after the disc has been put onto the supporting plate I.

A modified form of anchoring means wherein the metallic insert need not be threaded may be employed in that type of reinforced abrasive Wheel or disc in which the disc is secured to the backing plate by bolts inserted in the wheel through holes extending from the front grinding face of the wheel completely through the abrasive body and engaging a similar unthreaded anchoring insert and threading into the backing plate "w r e a.

itself. However, as in the case of the specific abrasive disc herein illustrated, the metallic insert of the anchoring means is inset from the mounting face of the wheel and provided with a non-metallic composition washer or filling material between the metallic insert and the mounting face. The anchoring means 8 are embedded in the bonded abrasive body 4 in such "position that the bottom side of the anchoring means lies flush with the mounting face 6 of the abrasive body. The number of these anchoring means embedded in any particular wheel or disc depends largely upon the size of the wheel, but also upon the conditions under which the wheel is to be used such as the speed of operation,.severity of the grinding operation, etc. They are distributed over the mounting face of the wheel and are usually evenly spaced from onelanother.

Each anchoring means consists of a strong, .tough,.threaded metal insert H, as, for example, a tapered steel nut, and-ha softer, more easily 'abradablewasher i2. The metallic insert H is preferably tapered and positioned with the large end of'the insert farthest away from the mounting surface of thewheel or-disc soas to be more strongly gripped by the surrounding abrasive "body. Instead of tapering the metal insert the outer'sides may beprovided with aseries of circumferential corrugations or otherwise provided with an uneven contour at the sides to enhance the-gripping action of the bonded abrasive body onthe insert. Thewasher 4 2-is made of softer material than the'me'ta'l insert and is placed between the metal insert lliand-the mounting face fi of thewheelandfiush with the latter. A composition washer-which has been found highly satisfactoryfor the-purpose is a plain unthreaded Temper d Masonite washer /8 thick. (Tempared Masonite is a-trade mark of theMasonite Corp-oration for material consisting of processed woodfibers compressed by heatand pressure and bonded by the resinous content-toe strong, hard conditions) Qther materials can be used providedthat they stand-up under the'temperatures employed "inmaturingthe bond of the abrasive body during the making of thearticle, and have the property-of wearing-away at a substantially equal rate with the surrounding abrasive body when the-two are subjected toalapping or comparabledressing operation. Materials which may be usedior washers include various organic compositions such as various fibrou's materials, synthetic resins, natural andsynthetic hard rubbers, asbestos-cloth base phenolic material, and the like. The kind of material used for the washer will depend mostlyon the nature of thebond of the abrasive body.

In making an abrasive article of the herein describedtype, such as that shown in Figures 1 and '2, the desired number of anchoring means, including composition washers and metal inserts are positionedin asuitable moldand the desired mixture of granular-abrasive and bond therefore plaoed in the mold about-the anchoring means. If desired, thewashers may be cemented to the metal insert prior to positioning in :the mold assembly, asuitable cement for such purpose being a liquid phenoli'c condensation product resin thinned with a suitable solvent. Before introduction of JPthe abrasive mixture into the mold about the anchoring means, :the latter are ipreferably coated with a thin liquidlcement such as bond for the abrasive article and also any auxiliary cementing or bonding means used in securing the anchoring means. In the case of organic bonds the bond may be partially or completely cured during the pressing operation although final cure is usually effected by an oven treatment at elevated temperatures followin the removal of the'formed article from the mold.

Instead of using a preformed composition washer and molding it into place along with the metal insert simultaneously with the molding of the bonded abrasive body, a modified procedure, particularly adaptable to the fabrication of ceramic bonded abrasive wheels and discs of the hereindescribed type requiring a high temperature firing to mature the bond, may be followed.

According thereto, the bonded abrasive body as molded and fired is provided with reentrant portions or cavities adjacent the intended mounting face and positioned the same as the anchoring means which are to be embedded therein but slightly larger in size than the latter. 'Ihese holes or cavities may be provided by molding the abrasive body about removable-inserts ofthetdesired size placed in the'mold prior to molding or about inserts which are readily decomposable at the temperature of firing. Such cavitiesmay also 'be provided by molding the abrasive body in solid form and drilling or otherwise forming the cavities while the bond i still in the unfired state. After the bonded body has been matured, and before or after the mounting face has been dressed to a substantially flat condition, the metal inserts and washers are placed in position in the cavities and grouted in place by means of a suitable cement such as a liquid reactive phenolic resin capable of cold setting with acid hardener and usually mixed with some inert filler. such as flint, fused quartz, air-floated asbestosetc. Ceramic bonded wheels or discs constructed by this method may have the inSerts-grouted with lead or a similar soft metal or-alloy-andthe composition washers inserted and grouted in place with a suitable organic cement as, for example, that given below. Grouting of the inserts in' this modified method for ceramic wheels is preferably that sometimes used incemen'ting the washer -to the metal insert. The mass is'then pressed to formed washers.

carried out with organic cements or alloys meltins; at a temperature lower than the melting point for lead since grouting with molten lead tends to warp the abrasive body. However, after grouting of the inserts and washers in place the mounting face of the abrasive disc can again be dressed flat, if necessary.

When abrasive wheels or discs are provided with anchoring means according to the above metal inserts from :being filled orsmeared with the filling composition by temporary'rinsertion'of a plug which can be removed afterfthe filler material has hardened. v

It is notunusual jforithe resulting abrasivetbiody tobe slightlywarped or distortedduringthe-Jouring or firing operation. Such warpage 'ishighly undesirable since a warpage as slight as two or three thousandths o'ian inch is suffi'ci'ent :to interfere with satisfactory mounting of the body on its supporting plate. The larger the wheel or disc being made the more troublesome the warping or distortion problem becomes. In order to avoid the necessity of discarding warped wheels of this type efforts are made to lap or otherwise dress the mounting face of the warped article to an acceptable degree of flatness for mounting.

Figure 3 is an exaggerated fragmentary view of an abrasive wheel structure made in accordance with the present invention and embodying anchoring means of the type herein described consisting of a tough insert II and a washer l2 of softer material. The anchoring means in Figure 3 is shown after it has been submitted to a dressing or lapping procedure to remove warpage of the article. The composition washer It has been worn down even with the surrounding abrasive body 4 so that the mounting face 6a, including the external surface lila of the washer, is flat and free from any projecting portions. It is to be understood that the excessive tilt of the anchoring means as shown in Figure 3 is thus pictured for purposes of clarity and the actual warpage which takes place is often up to A;, which however'must be removed if the article is to be rendered suitable for use.

As is clear from the above description, the present invention not only provides an abrasive wheel adapted for mounting on a fiat side face but also a method of reclaiming those wheels of the herein described type which become warped or distorted during processing, and which if otherwise constructed would either have to be discarded or at least restricted to much lighter usage because of poor mounting ability or weakening of the anchoring assembly durin subsequent dressing operations.

Having described the invention in detail it is desired to claim:

1. An abrasive article comprising a bonded abrasive body having a grinding surface and asubstantially fiat mounting face, said bonded abrasive body having embedded therein and substantially flush with said mounting face a plurality of anchoring means, each of said anchoring means comprising a metallic insert and a nonmetallic washer, the latter being disposed between the metallic insert and the surface of said mount- 6 ing face and substantially flush with the latter surface.

2. An abrasive article comprising a bonded abrasive body having a grinding surface and a substantially flat mounting face, said bonded abrasive body having embedded therein and substantially flush with said mounting face a plurality of anchoring means, each of said anchoring means comprising a steel insert and a nonmetallic washer, the latter being disposed between the metallic insert and the surface of said mounting face and substantially flush with the latter surface.

3. An abrasive article comprising a bonded abrasive body having a grinding surface and a substantially fiat mounting face, said bonded abrasive body having embedded therein and substantially fiush with said mounting face a plurality of anchoring means, each of said anchoring means comprising a metallic insert embedded within said abrasive body and spaced inwardly of the abrasive body from the mounting surface of said abrasive body, the intervening space between said metallic insert and the mounting face being filled with an organic composition substantially as easily abradable as the surrounding abrasive body.

l. An abrasive article comprising a bonded abrasive body having a grinding surface and a substantially flat mounting face, said bonded abrasive body having embedded therein and substantially flush with said mounting face a plurality of anchorin means. each of said anchoring means comprising a metallic insert embedded Within said abrasive body and spaced inwardly of the abrasive body from the mounting surface of said abrasive body, the intervening space between said metallic insert and the mounting face being filled with a heat hardenable resinous composition.

ROGER H. HOMEYER. I

REFERENCES CITED UNITED STATES PATENTS Name Date Gardner May 9, 1922 Number