US2329720A - Lapping tool - Google Patents

Description

Patented Sept. 21, 1943 LAPPING TOOL Foster F. Hillix, Lakewood, Ohio, assignor to The American Steel and Wire Company of New Jersey, a corporation of New Jersey Original application April 10, 1939, Serial No. 267,127. Divided and this application August 15, 1942, Serial No. 454,991

Claims.

This invention relates to improvements in lapping tools to be employed with granular abrasives for iinishing hard objects, such as steel metal-Working rolls and the like, this application being a division of my pending application, Serial No. 267,127, iiled April 10, 1939.

It is a prime object of my invention to provide a lapping tool or block which will uniformly distribute and apply a granular abrasive Without bunching, particularly with respect to the ends of the tool.

I have discovered that such undesirable bunching occurs with laps having a square end, that is, having all lap faces of the same length, the grain passing under the lap and causing accumulation and bunching of too much grain at the lap's end. It was at first concluded that this difficulty could be solved by chamfering the lap ends so as to permit the grain to slide under the lap and the lap to slide up and over the grains, but it was found that this idea did not work out entirely satisfactorily.

It was nally concluded that sharp ends on the lap prevented too much of the grain from entering thereunder, in itself a desirable condition, but would, in the absence of means to prevent lt, cause bunching of the grain at the lap ends, an undesirable condition. The first of these conditions, being desirable was retained, while the undesirable bunching effect was circumvented by relieving the land of the lap on one of its corners so as to provide the end thereof with an oblique face. This construction tends to pass the grain down along the end of the lap from land to land, admitting as much of it beneath the latter as is necessary, and by-passing the rest completely around the end and harmlessly to one side.

This improved lapping block construction may be better understood by reference to the attached drawing in which Fig. 1 represents a plan view of a typical block embodying the principles of the present invention; Fig. 2 being a cross-section thereof taken at line II-II, Fig. 1 Fig. 3 is a side-elevational View of the block as viewed from the left in Fig. 1.

In its preferred form, the block or tool may be composed of a body I of friable metal, as for example, a metal of the character described in my said parent application, although the benefits derivable from its oblique ends are not limited thereto, but extend to blocks used in any lapping operation; particularly, those in which loose grain is fed to the block on the work as described in my co-pending application, Serial No. 208,661, filed May 18, 1938.

The working faces of the blocks comprise lands 2, between which occur the valleys or grooves 3 into which cuttings and grain are, in part, retired, but which are provided principally to introduce lubricant and grain uniformly throughout the entire areas of the lapping faces. The lands 2 are progressively shortened to provide oblique ends 4 on the Work faces for reasons already set forth above.

Where the trend of movement of the block during a lapping operation is uni-directional of its axis, only the lead end need be cut away. However, since lapping operations are usually attended by poly-directional motion of the block, and, in the case of my previous inventions, above identified, the blocks are rapidly vibrated in axial directions, it is desirable to bevel both ends, as shown. In this connection, it should be noted that it is the corners of either the leading or trailing edge or side of the block that are truncated to give this effect, i. e., leading or trailing with respect to its advancement past the work with which it has relative movement.

This arrangement is adopted because the grain is applied to the work at the approach side of the block, and the latter, by reciprocating, scatters all grain not carried beneath it to the left and right until the oblique edges are reached. Here the grains that do not actually go under the block are rolled down from land to land, until discharged around the trailing corners thereof. The end-edges 5 of the lands are maintained as sharp corners to prevent more than one diameter of grain from entering between the lands and the work at one time. Thus is bunching of the grain precluded, and the depth of effective cutting grain maintained at a minimum, whereby only constant cuts of uniform magniture are made.

When composed of a friable metal of the character stated, the body I will have pores, voids, interstices, and/or grain boundaries, which, although too minute to be revealed to the naked eye, are, in fact, the spaces into which cuttings and grain are retired so as to leave the intermediate areas of metal clear of accumulations that ultimately bunch, become impacted, and scarify the Work. These minute areas of metal, when properly seasoned by use, become flat on top and charged with grains of the abrasive. It is this condition, when the grain is constrained to a depth of but one grain-diameter, that produces the highestl finishes. The effectiveness of these microscopic quantities might be questioned until it is realized that the abrasive grain employed is often as ne as one fty-thousandth of an inch in diameter, and the cuttings resulting therefrom of equally small magnitude.

The lap surfaces or lands 2 are thus composed of microscopic humps and hollows, which, by virtue of their metal composition, are maintained in this condition of greatest effectiveness due to their ability to disintegrate and wear away before becoming over-charged, impacted and useless.

The grooves 3 between the lands 2 are suitably proportioned relative to the latter so as to admit plenty of lubricant to the zones of work. The lands themselves must be of suihcient thickness to provide the strength required to maintain them in operation, but not so thick as to preclude lubricant from reaching the central portions thereof, since the lack of lubricant promotes seizing. bunching, impacting, and scarification of the work. A suitable width, susceptible of some variation, is one-sixteenth of an inch for the lands, and about the same amount for the valleys or grooves 2.

Various changes and modifications are contemplated within the scope of the following claims.

I claim:

l. A lapping tool or the like comprising a body having a working face including a plurality of alternate uni-directional lands and grooves extending throughout said iace, the said lands having adjacent ends disposed in oblique relation with respect to the said direction of the lands and grooves.

2. A lapping tool or the like comprising a polygonal body having a working face including a plurality of alternate uni-directional lands and grooves extending longitudinally throughout said face, at least one end face of the body being beveled transversely of the said lands and grooves to progressively shorten said lands.

3. A lapping tool or the like comprising a polygonal body having a working face including a plurality of alternate un-directional lands and grooves extending longitudinally throughout said face, at least one end face of the body being beveled transversely of the said lands and grooves to progressively shorten said lands, the corners of the lands formed by the lands and grooves being sharp to restrict access to said grooves from said end face of the body.

4. A lapping tool or the like comprising a polygonal body having a working face ineluding a plurality of alternate uni-directional lands and grooves extending longitudinally throughout said face, both of the end faces of the body being beveled transversely of the said lands and grooves to progressively shorten said lands.

5. A lapping tool or the like comprising a body having a working face including a plurality of alternate uni-directional lands and grooves extending throughout said face, the said lands being composed of a friable metal composition and having adjacent ends disposed in oblique relation with respect to the said direction of the lands and grooves.

FOSTER F. HILLIX.

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