US2420365A - Combination center punch - Google Patents

Description

M 1947- T. FISCHER 2,420,365

COMBINATION CENTER PUNCH Filed Oct. 2, 1944 75 504502; f ISCHE/B Inventor L:

I WM %3 Patented May 13, 194'? ED STATES PATENT OFFICE 3 Claims.

This invention relates to a novel and improved multiple-purpose or combination center punch such as is expressly adapted for use by tool makers, machinists and others in laying out work with a high degree of precision and accuracy.

More specifically, I have evolved and produced a simple and expedient, two-part punch characterized by a main center punch-point and companion radially and circumferentially spaced auxiliary punch-points, there being five points in all, whereby, under the force of a single stroke, five indentations are simultaneously made to provide center and concentric marginal markings for accurate drill placement and drilling results.

In carrying out the principles of the invention, I have evolved and produced a precision tool which, as far as I have been able to ascertain, is advantageous, far superior and otherwise aptly fitted to achieve the desired aims,'and especially the purposes covered in the concluding phases of this specification.

Other features and advantages will become more readily apparent from the following description and the accompanying illustrative drawing.

In the drawing, wherein like numerals are employed to designate like parts throughout the same:

Figure l is an elevational view of a multiple marking combination center punch constructed in accordance with the principles of the present invention.

Figure 2 is a view like Figure 1 with the adapter sleeve attachment shown in section.

Figure 3 is an elevational view of the attache ment or adapter sleeve per se.

Figure 4 is a bottom plan view of the sleeve seen in Figure 3.

Referring now to the drawing by distinguishing reference numerals, it will be seen that the complete assemblage is simply made up of two complemental parts; namely, the center punch proper, as indicated at A, and the adapter or attachment sleeve B.

The part A, as seen in Figure 2, comprises an elongated cylindrical body 5 with a suitable impact head 6 at its upper end, a substantially frusto-conical portion 1 intermediate its ends and an extension shank 8. The shank 8 is reduced at this juncture with the part 1 to define an annular abutment shoulder 9. The shank terminates in a conical end defining the main center punch-point ill.

The part B comprises an adapter sleeve of cylindrical form and of appropriate dimensions,

said sleeve i! being of a length greater than the shank 8 with its upper end l2 forming a thrust surface in contact with the abutment shoulder 9. The lower end terminates inwardly of the main punchepoint l5 and is provided with equidistant, circumferentially spaced auxiliary, but companion, punch-points it. There are five points in all. The pointed end of the sleeve is provided with diametrically opposite notches I3 which constitute sights for inspection purpose, as will be hereinafter pointed out. It will be noted that the adapter sleeve is held in place by a set screw it threaded into a screw-threaded hole provided therefor, the inner end of said set screw being blunt and frictionally contacting the associated shank 8.

As is well known, in order to drill a hole through or in a. piece of metal, or the like, at a certain designated spot, a conventional center punch is used to indent and form an impression at this spot to guide the drill point. However, after the drill has been started, no check is possible to see if the drill point has shifted and moved away from this spot, unless a circle is scribed around the center about the size of the intended hole and four small punches are made exactly on this circle. As the drill point then approaches these small punches, an uneven margin, seen by the eye, will indicate that the drill point has shifted and that the finished hole will not be in the intended location. By using a small half-round chisel, this can be corrected before the drilling of the hole is finished. scribing such a circle and punching the four additional impressions is clumsy, troublesome and very often inaccurate, aside from the fact that it requires a pair of good and sharp dividers to do this job. Scaly and very hard surfaces have to be chalked, in addition, in order to show the scribed circle.

My combination center punch eliminates the foregoing troubles. The hole to be drilled is laid out and the center punch is seated where the lines cross (center of the hole). The point where the lines intersect can clearly be seen through the slots, cut out at both sides of the removable attachment, which makes the four smaller punches spaced evenly around the center of the hole automatically. The center punch is t inch longer, making the outer four punches clear, but of less depth, only enough to note the margin between the half-started drill and the finished hole (diameter), which is represented by these four small impressions. v If the hole drilled is somewhat smaller and the four small impressions are not removed by the drill, they are harmless and will be covered by the bolt head or washer. If desired, the outer attachment sleeve can be removed by loosening the set screw. The force of the punch is carried by the reinforced shoulder of the center punch and the shoulder of the attachment sleeve. This face of the attachment can be ground ofi, if the center punch is reground, so as to maintain the ratio of depth of the main and auxiliary punch-points.

I am sufliciently conversant with center punches and similar tools to realize that patents have already been granted on coordinated multiple punch-points to facilitate marking for the laying out of various classes of work. However, and notwithstanding the development of the prior art, the tool herein shown, described and claimed is a novel contribution to the art. It is made of tool steel hardened throughout, and of the two details or parts A and B with a simple set screw. As emphasized, this tool produces all five punches in a single operation, the main point I entering first and the auxiliary points l3 promptly entering the surface thereafter, this all in a single stroke.

A careful consideration of the foregoing description in conjunction with the invention as illustrated in the drawing will enable the reader to obtain a clear understanding and impression of the alleged features of merit and novelty sufiicient to clarify the construction of the invention as hereinafter claimed.

Minor changes in shape, size, materials and rearrangement of parts may be resorted to in actual practice so long as no departure is made from the invention as claimed.

I claim:

1. In a combination center punch of the class described, a punch comprising a body having an impact head at its upper end and a shouldered shank at its lower end, said shank terminating in a main centrally and axially disposed punchpoint, and a sleeve on said shank abutting the shoulder and provided with circumferentially spaced auxiliary punch-point disposed radially and in circumferentially spaced relation with respect to the mainpunch-point, said sleeve being provided with a set screw for removably holding same in place on said shank, and further provided with diametrically opposite notches, said notches constituting sight openings to permit inspection of the main center point.

2. In a, combination center punch of the class described, a punch comprising a body having an impact head at its upper end and a reduced shank at its lower end providing a shoulder, said shank terminating in a main centrally and axially disposed punch-point, and a sleeve fitted on said shank and abutting, at its inner end, said shoulder and provided with circumferentially spaced auxiliary punch points, these located at the outer end and being disposed radially and circumferentially spaced in relation to said main punch point, said sleeve being held removably in place by a fastener, said sleeve being further provided with sight openings, said sight openings serving to permit inspectionof the main center punch point while the tool is in operation,

3. As a new article of manufacture and as a component part of a punch of the class described, an elongated sleeve adapted to fit over a shank on an associated shouldered punch, said sleeve being adapted, at its inner end, to abut the shoulder on said punch, said sleeve being provided with a set-screw to facilitate maintaining the sleeve in place, said sleeve being provided at its outer end with integral circumferentially spaced auxiliary punch points, these for co-action with the main punch point on the aforementioned punch, said sleeve being also provided at its outer end with diametrically opposite notches and said notches constituting sight openings.

THEODORE FISCHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,314,184 Clark Aug. 26, 1919 925,978 Bacho et a1 June 22, 1909 1,299,210 Myers Apr, 1, 1919 1,306,013 Kershaw June 10, 1919 OTHER REFERENCES Martinsen, Tool for Laying Out Work, April 11, 1929, American Machinist, vol. 70, N0. 15, p. 604.

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