US2799980A - Grinding wheel assembly - Google Patents

Description

July 23, 1957 e. F. KEELERIC GRINDING WHEEL ASSEMBLY 2 Sheets-Sheet 1 Filed Nov. 25, 1953 U. II VI,

July 23, 1957 G. F. KEELERIC GRINDING WHEEL ASSEMBLY 2 Sheets-Sheet 2 Filed Nov. 25, 1955 the diamond'powder. 1 great deal of cutting, the life of such tools'is shorter than conventional diamond grinding wheels of the prior United States Patent GRINDING WHEEL ASSEMBLY George F. Keeleric, Dundee, Ill.

Application November 25, 1953, Serial No. 394,349

4 Claims. (Clf51-209) This invention relates to abrasive tools and has as its general purpose the making of fast-cutting abrasive tools of great accuracyand of'verylow cost. It has particular value in applications where costly diamond powder is used as the abrasive, although it is not confined to this 2 application.

In diamond grinding, it has been the practice to provide Y diamond-bearing grinding 'wheels, usually made with powdered metal or vitrified or plastic bond. These grinding wheels must be made with accuracy if accurate grind- T he single-layer diamond wheels, such as those made .inaccord'ance with my Patent No. 2,368,473, issued Janu'ary' 30, 1945, for Method of -Making Abrasive Articles, 7 also have required careful truing up. This requires several costly operations in manufacturing, and it requires labor and care atthe point of use. Thefact is, however,

that-the working part'of these single-layer diamond grind ing wheels'can be'made quite inexpensively-4f the costly operations of making the mounting wheels is-not ineluded.

'Also, it has been found that such single-layer diamond grinding wheels will cut at'very high rates if the diamond particles are arranged properly, as for example in my co-pending application: Serial No; 357,483, filed 'May '26, 1953, now abandoned, for Abrasive Tool and Method of Making Same, or in the continuation thereof, Serial No. 394,348, filed November 25, 1953, for AbrasiveTool andMethod Making Same.

Such arran'gements result in the use ofvery few diamond particles in each tool, and this, of course, reduces their cost. It results in a very complete and efficient use of But since each particle does a art. Accordingly, it is desirable to find a means of avoiding the'making ofcomplete grinding wheels in order to replace a consumable portion which represents only a part of the cost of a complete wheel.

The object of this invention is to provide a way of meeting the considerations 'just stated.

More particularly, it is an object of this invention'to provide removable and replaceable diamond grinding elements of great accuracy which are inherently easy and cheap to make.

Another object is to provide for quick and easy removal of-one of the abrasive-surface elements and its replacement by another.

Another object isto provide thin, light, flexible rings carrying abrasive particles and responsive to the magnetic attraction of a magnetic chuck.

2,799,980 Pate'nted Jul 23, 1957 A somewhat different object is achieved at the same time. This is a cushioning or shock-absorbing efiectwhich gives what operators call a sof feel. Experienced operators reportthat some diamond grinding wheels have a soft feel; others a hard feel. Thus, the so-called resinoid or plastic-bonded wheels have a soft feel, while certain metal-bonded wheels have a hard feel. The soft feel is much preferred, and this seems to be more 1 vthan-whim, for sharper edges can be produced with a soft wheel. This may be because the softer bonding material yields somwhat as the abrasive particles engage the work, and thus reduce the grinding shock so that the edges of the workpiece being cut' are not roughened by tiny nicks chipped away by the impact of the abrasive particles.

- Butwhetheror not this analysis is correct, his com- -mercially desirable to obtain the soft feel in such grinding wheels.

Yet there are many advantages to a hard metal bond, particularly the fact that better holding of abrasive particles is obtained, thus reducing the waste resulting from dislodgement of'particles. And it is an object of this invention to obtain a soft feel while retaining the advantages-of a metal bond in holding the abrasive particles.

The crux of the invention lies in making a thin ring or annulus of nickel-or iron, which serves as a bond for the abrasive particles, and in making a cooperating chuck with appropriate interlocking means which permits rotary "slippage but, at the same time, centers the ring on the chuck and prevents its' fiying off under use. The interlock arrangement intentionally provides for a slight pared with complete grinding wheels.

amount of rotary or circular slippage of the ring relative to the chuck, so as to minimize grinding shock and give a'soft feel. 'The low mass of the abrasive-bearing ring is a factor in achieving this result.

rings can be reclaimed for'further use after the abrasive 7 that is, they need not themselves be magnets.

particles are worn'down', and this is another object.

Other objects will appear in the description of the invention which follows.

In the drawings: Fig. 1 is a perspective view of an abrasive-bearing ring of th1s invention.

Fig. 2 is a sectional view of a magnetic chuck made to cooperate with the ring of Fig. 1, taken along the line AA of Fig. 3 and showing the abrasive-bearing ring of Fig. 1 in place.

Fig. 3 is a sectional view taken along the line B-B of Fig. 2 and showing virtually a plan view of the magnetic chuck.

Fig. 4 is a plan view, partly in phantom, of a modified form of chuck.

Fig. 5 is a sectional view, partly in phantom, of the chuck of Fig. 4 taken along the line CC.

Referring to Fig. 1, the ring proper 1 is preferably made of nickel or iron or other material, which will be held by the magnets of a magnetic chuck. Such materials are referred to here as magnetic, although they are so only in the sense of being attracted by magnetic force;

Protruding from the working surface of the ring 1 are abrasive particles 3, which are imbedded in and held by the metal or a portion of it. These particles are shown much enlarged in Fig. 1. In actuality they are scarcely visible except as bright points of reflected light. If it is preferred,

to permit this.

"to use a material like bronze as a bonding metal, this'may be done, and then an iron or nickel ring may be soldered to it. It is desirable to keep the thickness of the ring to a minimum in order to save cost, to reduce mass and,

' also, to minimize any problem of rotating unbalance.

In practice,the rings may be less than %& in thick- J ness and still be strong enoughto be easily handled.

Moreover, if the metal is thin enough and flexible enough,

it will be flattened by magnetic attraction of the chuckand will run true. The same result in this respect-might be obtained by making the ring thick enough and rigid enough so that it 'will not be distorted, but this is not preferred. What must be avoided is to make the ring just weak enough asto'be easily bent slightly out of shape by handling yet not flexible enough to be pulled flat when laid against the magnetic chuck.

- 7 Depending from the surface of the ring opposite the abrasive-bearing surface arethree studs 5. These may take the form of round pins, as shown, and. may be soldered, brazed or resistancewelded (e. g., spot welded or projection welded) to the ring 1. It is preferable that welding'be used and that the studs 5 be of the same material as ring 1. Or they may take the form of segments of a ring of rectilinear section and may register with an annular slot in the magnetic chuck.

It isimportant that the ring 1 be of uniform thickness from its working surface to its chuck-engaging surthe way around the ring.

. a The ring 1 may be made following some of the disclosure of my aforementioned Patent No. 2,368,473, and

achieved in other ways; for example, the ring may be made of powdered metal, following the usual molding and sintering practice. Nickel powder or iron powder or various combinations which provide a magnetic material may be used. Or a thin bonding layer of bronze powder may be used, which will then be backed up by a ring of nickel or iron or other magnetic material, the two parts being attached by soldering or sintering or cementing. It has been found, however, that the electrolytic method gives an excellent result. Attention should also be given to the fact that one of the important uses of the invention lies in the establishment of an arrangement of a relatively small number of diamond particles on the working surface of the ring, preferably arranged in a desirable cutting pattern, all with the intention of increasing the cutting rate but with the recognition that the life of the working surface is thus reduced.

Once the ring has been ground or otherwise Worked to a'uniform thickness (in the circular sense) then the interlocking studs 5 are attached. The studs and the ring are located in a suitable jig and welded or soldered with 400 F;. solder.

' It will be seen that by this means a very inexpensive abrasive element is produced, characterized'by great accuracy in the uniformity of thickness.

Turning now to the chuck with which the ring coi operates, the best general understanding will be had by reference to Figs. 2 and 3 taken together.

A-strong wheel body 11, made of brass, aluminum or other non-magnetic material, is machined to provide a center aperture '13, four mounting hole 15, and eight 7 tapped truing holes 17. If desired, the truing holes may be omitted and the truing accomplished by shims between the wheel member 11 and the mounting plate of a grinding machine, all in the conventional way. The center aperture is adapted to fit closely over the end of a grinding spindle which ordinarily protrudes from a mounting may embody the invention of the continuation of my aforesaid co-pending application, Serial No. 357,483.

Thus, a carefully made plating blank is coated with adhesive, and a pattern of diamond particles is placed on it. Then, a thin layer of copper is electrolytically deposited through the adhesive, which must be thin enough The copper layer is usually only a few thousandths of an inch thick-sometimes less than one plate fastened to the spindle. The mounting plate is conventionally provided with four tapped holes which all register with the mounting holes 15. In practice, the

I chuck is slipped over the end of the grinding spindle and against the mounting plate, and screws or bolts are passed through holes 15 and screwed into the tapped holes in thousandth.v In any'case, it will coverthe particles to ment of any supporting iron ring or other special provision to this end. .At some later stage in the operations, the thin layer of copper is removed so as to expose the abrasive particles to a depth equal to the thickness of the copper.

The back surface of the nickel is then ground flat and smooth in a grinding machine. This may be done most advantageously before the nickel ring is stripped from the plating blank. The blank carrying the nickel layeris set on the table of a surface grinder with the nickel toward the grinding wheel. Since the blank is itself carefully made and of uniform and known thickness, the grinding operation can be used to establish both the desired dimension and uniformity of thickness in the ring.

' After this operation, the,ring may be stripped from the blank and is finished except for adding studs 5 and removing the thin copper layer.

It is possible, of course, that the .same. result may be the mounting plate.

The wheel body 11 has an upraised portion around its periphery into which a groove 19 is cut to a depth of about /8 and to a width to permit'receiving a number of U-shaped, permanent magnets 21. Each of these magnets is fastened by a screw 23 to the wheel body 11. The magnets are arranged in a shifting pattern of polarity as indicated by the designations N and S on the pole faces (Fig. 3). V

The groove 19 is adapted to hold, in addition to the magnets, three brass inserts 25 fastened with screws or rivets 27. 7

These inserts are used to form a part of the interlock arrangement between the chuck and the abrasive ring 1.

. Each insert 25 is drilled with an elongated hole 29. The

hole may be formed by use of a combined end mill and side-milling cutter which is first drilled through to form a hole. .Then the insert is moved about a radius equal to the radius taken from the center of the chuck, so that the elongated hole 29 has sides which are segments of" holds for easy removal of abrasive ring 1.

Once the magnets 21 and the inserts 25 have been set and fastened in place (but before rubber bushings 28 i have been pressed in), the spaces between the magnets and in the yokes of the magnets, etc., are all filled with a suitable .filler,, such as a thermosetting plastic 26. It has been found that a thermosetting plastic which sets at about 300 F. is suitable, and the plastic is mixed with aluminum powder or the like to produce a more durable surface and to reduce cost. .After the spaces have been filled and the plastic has been set by curing, a grinding cut is taken across the whole surface so that pole faces of magnets 21, the faces of inserts 25, and the filler 26 are all flush and flat.

Within each elongated hole 29, a rubber bushing 28 is inserted having relatively thin side walls and thicker end walls. Clearanceis provided at the upper end of the rubber bushings to permit the rubber to deform without flowing up-against then'ng 1. The purpose of these bushings is to permit. interlocking pins or studs 5, which are fixedly mounted to ring 1,-to move somewhat in response to torsional stress brought about by actual grinding operations. While in Fig. 3 the studs 5 are shown in a central position, under running conditions the ring 1 and the studs 5 are displaced by the drag of a workpiece against the abrasive ring, so that the studs 5 push against one or the other ends ofthe rubber bushing 2 3 depending, of course, upon the directionof rotation. In responseto thelittle shocks set up as the diamond particles encounter a workpiece, ring 1 is displaced rotationally, and this-displacement is cushioned by the resiliency of rubber bushing-28. Thestrength of the magnetic attraction is appropriately adjusted by the size and strength of the magnets-and-bythe-flux path-provided through ring 1, so that-some-slight'amountof slippage in response to grinding shock is permitted.

There are many'alternative variations of accomplishing this same result. For'example, as" shown in Fig. 4, the insert elements 25" may be 'omitted and an annular groove 41 provided;'falling within'the yokes of the magnets. The groove is of a depth and width to accommodate pins 5. If necessary, the pins may be made smaller and shorter than shown to fit within the groove. The groove is preferably defined by an annular, U-shaped, brass member 43, as shown in Figs. 4 and 5. This provides a smooth and durable engaging surface. If desired, the plurality of individual magnets may be replaced with a single, continuous, circular- U-sectioned magnet magnetized in such a way that the inner limb constitutes one pole and the outer limb constitutes another, and, if desired, the yoke section of such a magnet may serve as the interlocking groove for registry with a depending ring attached to ring 1. Or again, the wheel body 11 may be formed with the inner lip of the magnetreceiving groove 19 extending slightly above the level of the magnets and fitting closely inside ring 1.

What is characteristic of any of these arrangements is that some degree of slippage is intentionally provided between an abrasive-bearing member 1 and a more or less rigid wheel body 11, while at the same time the abrasive-bearing ring is held against the forces tending toward radial displacement and is given a firm backing against any substantial axial displacement. The ring must be free to yield to rotational shock. It must not yield to radial displacement, as if it did it would cause unbalance. And it must not yield to pressure against axial displacement except in minute degree. Of course, it is impossible to achieve perfect rigidity in any direction, but the intention is that the axial and radial displacement permitted be very small as compared with the rotational displacement permitted.

Once the magnetic chuck of this invention is fitted to a grinding spindle and trued up, there is little occasion to need adjustment except in the case of abuse or accident. The operator is provided with a number of the abrasive-bearing rings. All that the operator needs to do is to Wipe the face of the chuck clean and likewise the mounting surface of abrasive ring 1, which is then quickly slipped into place and is instantly ready for use. During use, the slight amount of slippage which is provided gives a soft feel to the grinding wheel and is helpful in imparting sharp edges to the workpieces where these are important. The actual amount of slippage may be kept very small,.usually less than 1% of the wheels rotation,-and stillbe effective. Where rubber bushings are used, the slippage is restored aftereach shock by the resiliency ofthe rubber.

When the abrasive-bearing ring becomes worn so that it no longer cuts rapidly, or, in the case of a contoured ring for shaping purposes, when the desired contour is lost, it is only necessaryto slip the used ring off the chuck, moving it axially to do so, and then to replace it with a new ring.

This saves time that would otherwise have to be spent in redressing a conventional wheel and, ultimately, in replacing it and, possibly, having to trueit up.

'The abrasive-bearing rings may readily be reclaimed. This is particularly easy if the studs 5 (or whatever other interlocking members serve their purpose) are made of the same material as ring 1. As the diamond particles wear flat on their protruding surfaces, so that the cutting speed of the tool decreases, the ring is removed from the grinding machine and is returned in its entirety to the factory. The rings are cleaned and may then be used directly as anodes in an electroplating bath for the making of new and additional tools, presumably of the same kind. As the metal of the abrasive-bearing rings is dissolved into the plating bath, the diamond'particles which remain fall to the bottom of the container for the bath and may, fromtime to time, be recovered, washed, dried and rescreened. It is found that a great many of the particles may beused again without any disadvantage whatsoever, for it is very unlikely that any substantial number of the particles will be aligned in new tools with the surfaces flattened -byprevious use .in cutting position. As a practical matter, the reclaimed diamond particles are usually used in a mixture with new diamond particles. One of the reasons for preferring to use studs 5 which are made of the same material as ring 1 and for using welding rather than soldering to attach them is that in this way it is not necessary to remove the studs and to clean away the solder before the reclaiming begins. The reclaiming is particularly desirable, of course, where the material used is nickel or other material which has substantial value and may, from time to time, be in short supply.

Thus, there is provided a means for using very fastcutting, diamond-bearing abrasive tools, of manufacturing them at very low cost, of using them with a very minimum of loss of time in dressing or changing tools and with a maximum saving of material.

While a preferred embodiment of this invention has been shown and described, it will be apparent that numerous modifications and variations thereof may be made without departing from underlying principles of the invention. It is therefore desired by the following claims to include within the scope of the invention all such variations and modifications by which substantially the results of this invention may be obtained through the use of substantially the same or equivalent means.

What I claim as new and desire to secure by Letters Patent is:

1. As a new article of manufacture, a grinding wheel assembly comprising a magnetic chuck adapted to be mounted on, and driven by, a power driven shaft and consisting of a disc-like body provided on the central portion thereof with means for connecting it to the shaft and embodying on its outer marginal portion a laterally extending ring-shaped enlargement having formed therein a comparatively deep concentric annular groove and provided with means forming a smooth fiat annular driving surface in concentric relation with the chuck body and at the side of the groove that is farther from the chuck body, an annular series of separately formed spaced apart permanent magnets mounted fixedly in the groove and arranged so as to set up attraction-type magnetic lines of force through the driving surface, a removable separately formed lightweight ring-shaped grinding member contoured substantially conformably to, and fitting normally 7 flatly against, the driving surface, retained yieldingly in chuck body while at the same time permitting'the grinding member to rotate relatively to the said chuck body about the latters axis, said permanent magnets being preand in which the mechanical interlock means for positively holding the grinding member against radial displacement with respect to the chuck body serves also to limit rotative displacement of the ring-shaped grinding member with respect to the chuck body and consists of a plurality of spaced apart elongated arcuate holes which intersect and extend inwards from the driving surface, and a plurality of studs which are fixedly connected to the inner surface of and project at right angles to the ring of the grinding member, correspond in number to and are associated respectively with the holes, project into the holes, and are so proportioned that they are movable lengthwise of the holes in connection with rotative displacement of the grinding member with respect to said selected in such manner that their combined magnetic, l5 grinding surface.

power of attraction is so proportioned and correlated to the grinding member that when a workpiece to be ground is initially and normally placed against the layer of abrasive particles in connection with a workpiece grinding operation the grinding wheel in response to grinding shock is permitted to be rotatively displaced to a limited extent only relatively to said driving surface.

2. A grinding wheel assembly according to claim 1 and in which the body of the magnetic chuck is formed of non-magnetic material and the abrasive particles of,

the ring-shaped grinding member are diamonds.

3. A grinding wheel assembly according to claim 1 and References Cited in the file of this patent UNITED STATES PATENTS Morrison June 1, 1875 224,623 Allen Feb. 17, 1880 2,056,182 Gardner Oct. 6, 1936, 2,226,506 Van Der Pyl Dec. 24, 1940 2,241,585 Day May 13, 1941 2,347,920 Mays May 2, 1944 2,361,492 Pare Oct. 31, 1944 2,368,473 Keeleric J an. 30, 1945 2,388,020 Suwa Oct. 30, 1945 2,408,220 Lum Sept. 24, 1946 2,424,140 Beecher July 15, 1947 2,496,352 Metzger Feb. 7, 1950 2,505,196 Mays Apr. 25, 1950 4, 2,506,556 Ball et a1 May 2, 1950

Images