US2257441A - Self-tapping drain plug or bolt - Google Patents

Description

S p 1941- E. L. WYLIE 2,257,441

SELF-TAPPING DRAIN PLUG OR BOLT .Filed Jan. 4, 1941 F/6.1 F/6.Z

ATTORNEY Patented Sept. 30, 1941 SELF-TAPPING DRAIN PLUG OR BOLT Ernest L. Wylie, St. Louis, Mo., assignor to Champ-Items Inc., St. Louis, Mo., a corporation of Missouri Application January 4, 1941, Serial No. 373,106 1 Claim (01. 85-47) When this occurs'a costly labor job results,-

because it is almost impossible to use the next larger tap, either S. A. E. or U. S. S., owing to the fact that in many instances the amount of metal in the crankcase is insuflicient to permit the use of an oversized tap. Furthermore it is not considered practical to put an ordinary machine screw without a gasket in the oil pan or crankcase and expect to make a satisfactory repair.

The principal object of my invention is to provide an oversized drain plug which is so constructed that it will cut its own threads as it is inserted in the aperture from which the threads have been stripped.

A further object of my invention is to so construct the plug that it can be removed after the thread has been cut and the chips removed when the plug itself which has been used as a tap can then be re-inserted and used as a drain plug, a special gasket being furnished for this p pose.

A further object of my invention is to so construct the plug that the heel of'each portion of the'plug which cuts the threads will be sumciently low to free the chips resulting from the threading operation.

My means of accomplishing the foregoing obf iects maybe more readily understood by having reference to the accompanying drawing which is out axial displacement.

Similar reference numerals refer to similar parts throughout the entire specification.

As shown in the drawing, I form my improved drain plug from bar stock on a regular screw machine (not shown).

After the plug has been cut oif it is placed in a milling machine andtwo transverse slots 2 and 3 are milled in the threaded portion 4 of plug I. These slots 2 and 3 are at right angles to each other and pass through the axis ofthe plug I as clearly shown in Fig. 1 and Fig. 2. It has been found in practice best to make these slots to extend approximately one half the length of the plug.

After the slots are milled the plug is placed in a punch press and a special cam ground conical punch is employed to swage the four ends 5, i, I, and 8, upwardly as illustrated in Fig. 4. An examination of this Fig. 4 of the drawing will show that the heel 9 of each of the four ends is lower than the cutting edge ID of the threads. The plug is then hardened and tempered and is then ready to be used for the purpose intended.

By compressing the ends of the plug after it has been threaded the cutting edges or points iii are caused to bite the metal firmly when cutting the new thread, thereby insuring a perfect thread in the crankcase or oil pan. The plug is provided with the usual hexagonal head ll, al-

though obviously the shape of the head is largely a matter of choice provided it is so shaped that a tool can be employed to tighten it.

I have found in practice that it is desirable to have a plain or unthreaded portion I2 adjacent the head II, on which to mount a gasket it.

Having described my invention what I regard as new and desire to secure by Letters Patent is:

A self-tapping drain plug comprising a head, a unidirectional-portion tapered laterally, said portion being threaded for tapping and having two transverse slots'intersecting along the axis of the plug therein set at thereby forming four segmented portions. said segmentedportions each being swaged inwardly along one of its plane faces thereby exposing four cutting edges with- ERNES'I L. WYLIE.

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