US369248A - Boring bit or drill - Google Patents

Description

(No Model.)

F G. JOHNSON.

BORING BIT OR DRILL. No. 369,248. Patented Aug. 30,1887

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FRANK O. JOHNSON, OF BOSTON, MASSACHUSETTS.

BORlNG BlT OR DRILL.

SPECIFICATION forming part of Letters Patent No. 369,248, dated August 30, 1887.

Application filed August 25, 1686. Serial No. 211,701. (No model.)

drill having a cruciform shank with lateral flanges swagcd thereon without removal of any of the metal, as hereinafter described.

These flanges are made somewhat thicker and narrower near the end of the shank than elsewhere, the whole construction serving to stiffen and strengthen the shank and to give a firmer hold upon it by the bit stock or holder in which it is inserted for use. In some cases I reduce the diameter of the end of the shank, as a step preliminary to swaging it into the cruciform shape peculiar to my invention. By this practice bits or drills of large caliber, which otherwise would not enter the stock or holder, are made at the end of the shank of proper size to enter and 'be held by it.

The drawings illustrate my improvement, showing in Figures 1 and 2 a drill in two different posit-ions, and in Fig. 3 a section of the shank at as a", Fig. 1. Fig. 4is a drill with reduced shank, and Fig. 5 the same with my improvement.

A represents the body of the bit or drill, having at its working end any desired form or construction, and at its opposite end the construction peculiar to my invention. This peculiarity consists in the cruciform shank 13, having swaged flanges formed at and near the end of the tool by a lateral displacement of part of the metal without removing any portion thereof, and by leaving between said flanges a tongue or rib, d, of the metal undisturbed along a central plane of the shank. By this construction the fiangesc are formed, mainly, of material forced laterally from its original position within the periphery of the cylindrical end of the drill into a new posit-ion partly outside of such peripheral line and partly within it, and the transverse section of the end of the drill is transformed from a circular to a cruciform outline, as indicated in the drawings. The lateral flanges c retain as their surface material the skin or outer coating belonging to the drill end before their formation, and the-metal lying within this skin is compacted by the swaging blow and made of increased strength.

The rib d, which is left standing vertically between the parts depressed or compressed and laterally displaced, is slightly lessened in its height or diameter, due to the compression exerted on the adjacent metal. Thus while the flanges c are by the swaging blow thrown somewhat outside of their original peripheral circle, the ribs (1 are drawn slightly within it. 1

It will be understood that the dies by which this cruciform character is given have each a central recess the converse of and corresponding to one of the ribs cl, while the face of the die is otherwise smooth to correspond with the Hat or slightly-curved surface of each flange c. The faces of the dies will be not quite parallel when at the innermost limit of their stroke, so as to make said flanges thickest at and near their outer ends and tapering slightly therefrom. This peculiarity is advantageous in giving the gripping device of the bitbrace or tool-holder a firmer hold upon it when in use.

The tool, having flanges gradually increasing in thickness toward their outer ends, cannot be disengaged from the chuck or holder when its jaws are closed upon them, and hence will not pull out when in use.

It is obvious that my improvement is applicable to awls, files, chisels, gonges, and a variety of similar small tools which in use are inserted in a removable handle.

Fig. 4 represents a drill the end of which has been reduced in diameter before forming the flanges c and ribs (1 on it, so that when subsequently formed they will not be toolarge for the capacity of the holder. Fig. shows the tool formed by the two successive operations, the tapering or reduced neck e indicating the decrease in diameter. A single blow of the swaging-dies is sufficient to form the ribs and flanges in either case.

Tools with cruciform shanks have heretofore been made by milling out and cutting away the metal lying between the. four arms of the cross, thereby breaking the skin and removing part of the metal without relocating and compacting any portion of it, thus weakening instead of strengthening it, and

cruciform shank, the two flanges o of which gradually increase in thickness toward their outer ends, substantially as and for the purpose set forth.

In testimony whereof I have signed my name to this specification,in the presence of tWo subscribing witnesses, on this 23d day of August, A. D. 1886.

FRANK G. JOHNSON.

' Witnesses:

A. H. SPENCER, WV. J. J OI-INSON.

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