US2052019A - Separable drill bit - Google Patents

Description

Aug. 25, 1936.

,L B. BAKER sEPARABLE-DRILL BIT Filed Dec. 26, 1951 Patented Aug. 25, 5.11936.)

. UNijr'En s SEPARABLE BREIL BIKE' John B. Baker, Canton, Ohio, assigner to The Timken Roller Bearing Company, Canton, f 0hio,-a corporation ci (Ehio Application December 26, 1931, Serial No. 583,256

2 Claims.

separable drill bit and inthe parts and combinations and arrangements of parts hereinafter described and claimed. e

In the accompanying drawing,

Fig. 1 is an elevation of a drill rod and separable bit provided with threaded portions embodying my invention, the bit being shown in section,

' Fig. 2` is a similar view showing the parts separated.

Fig. 3 is an enlarged diagrammatic view showing the thread contours,

Figs. 4 and 5 are views similar to Figs. 1 and 3 of a modiiled thread construction, and

Fig. 6A is a view similar tojEig.v 1 showing a washer at the end ofthe drill rod.

Great diiliculty has been found in making.

threaded -bits `which will not bind upon the threaded end of the drill rod. Various thread..

structures have been devised, such as a. thread having a substantially continuous curved contour. In all previous constructions, however, repeated impact tends to flat-ten out portions of the sides of the threads and pack `the metal into tane spaces at the crest and hollows of the threads, thereby causing the parts to become tightly jammed together and frequently causing the parts to break.

According to my invention,I the tendency for the middleportions of the threads to become attened is obviated and the parts continue to beV separable under the most severe usage.

The drawing illustrates the `usual hexagonal drill rod l having a threaded end A cooperating with 'the threads B .of an interiorly threaded vbit member 2. The threads A and B have a generally curving contour.' One thread, illustrated 'as being the thread A of the drill rod has the-crest 3 thereof provided with a rakiius'of curvature R. that is greater than the radius of curvature R.' of the base portion. Thus, the crest 3 of the thread A of the drill rod is wide and at ascompared with the,. curve of the base portion of the thread and as compared with the trough 4 between the base portions oi' the threads A. The crest 5- of the other thread B has a shorter radius of curva.-v

. portions of said threads being different from the" 'ing to the space between threads of the other portionof the thread of said drill rod being' greater than the radius of curvature ofthe inner portion (CH. Z55-64) ture r than that 1'" of thread B.'

Both threads A and B are provided with dattened bands 6 along their sides. The width of these iiattened bands or zones 6 is preferablir a 5 little less. than one-third. of the linear surface distance from the center of the crest of the thread tothe center of the trough between' threads.

' By reason of the differences in curvature of 10 the different portions of the thread, the threads A 4and B are not symmetrical with reference to the base portion of the the diametrical pitch line P. In other. Words the Apitch line does not bisect the thread contour.

In the modiiication lshown in Figs. 4 and 515 the trough between the threads 3A of one member is filled out to form a flat surface 4 beginning approximately at the bottom of the flattened bands 6' of adjacent threads. 'Ihe crests 5 of the cooperating threads b of the other member are correspondingly attened.

As shown in Fig. 6, an annular washer 1 may be interposed between the end of the drill rod I and the bit 2. This washer serves to cushion lthe blows and accommodates any inaccuracies in. the shape ofthe end of the drill rod and the end of the bore of the bit. f

The above described thread con/struction `does not bind or jam under the most severe usage. The threads are not battered out of shape and hence the threads do not bind. The difference in curvature at the crest and at the base of the threads permits compensation for difference in the strength of the materials of which the drill lrod and bit are made.

What I claim is:

1. A separable drill bit construction comprising a threaded drill rodand an interiorly threaded bit thereon, the radius of curvature of the outer 40 radius of curvature of the inner portions of said threads, thereby giving the thread a prole diiferent from the profile of the space between threads and the thread of one member conformmember. 2. A separable drill bit construction comprising a threaded drill rod and an interiorly threaded bit thereon, the radius of lcurvature of th outer of said thread' and the thread of said bit being shaped to vconform to the space between threads of said rod. I

JOHN B. BAKER..

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