US2955804A

US2955804A - Drill bit

Info

Publication number: US2955804A
Application number: US711517A
Authority: US
Inventors: Jacob E Feucht
Original assignee: Westinghouse Air Brake Co
Current assignee: Westinghouse Air Brake Co
Priority date: 1958-01-27
Filing date: 1958-01-27
Publication date: 1960-10-11
Anticipated expiration: 1977-10-11

Description

Oct. 11, 1960 J. E. FEUCHT 2,955,804

2 INVENTOR. JACOB E. FEUUHT BY m, m Wdw United States Patent DRILL BIT Filed Jan. 27, 1958, Ser. No. 711,517

4 Claims. (Cl. 255-64) This invention relates generally to drills and more particularly to a drill bit and drill steel, and the connection therebetween, of the type in which the bit is slipped over the tapered end of the steel to form a wedge fit therewith.

In conventional drills of this general type the drill steel frequently broke on its connecting portion. When this occurs, the drill steel must not only be reconditioned, but the hole which was being drilled may be lost. Furthermore, the bits themselves frequently break by the wedging action of the drill rod, when the latter is driven by the pneumatic drill to which it is attached.

A tight wedging fit is required between the drill rod and bit in order to form a seal therebetween which insures that cleansing fluid is ported from the center of the drill rod through the holes in the bit.

In accordance with the present invention an improved bit and steel connection is provided which prevents stressconcentration in the connection portion of the drill steel and in the bit and consequent breakage thereof.

More particularly, the tapered skirt of the bit extends beyond the complementary tapered surface of the rod and around a portion of the rod that is non-circular in cross section. Thus the stresses set up primarily in the connection portion of the drill steel are distributed and thereby prevented from being concentrated in any one section.

In addition, the invention further contemplates that the skirt portion of the bit is made of more ductile steel than the cutting edges thereof and the skirt may deform slightly over the non-circular portion of the rod. This deformation not only contributes to reduce stresses at the connection point but also prevents the bit from rotating on the drill.

A drill bit and rod have been provided in which a sealing press fit is formed therebetween and which further distribute stresses in the bit at its connection point so as to prevent breakage thereof.

These and other objects and advantages will appear hereinafter as this disclosure progresses, reference being had to the accompanying drawings, in which:

Figure 1 is a side view of a drill bit and rod made in accordance with the invention, the bit being in section, and the view being taken along line 11 of Figure 3;

Figure 2 is a view similar to Figure 1, but on an enlarged scale and showing both the bit and rod in section, the view being taken on line 2-2 of Figure 3;

Figure 3 is a sectional view, on an enlarged scale, taken on line 33 of Figure l and showing the deformation of the bit skirt from its original broken line position; and

Figure 4 is a cross-sectional view, on an enlarged scale, taken on line 44 of Figure 1.

Referring in greater detail to the drawings, the drill rod 6, or drill steel as it is commonly referred to, is generally of non-circular cross-sectional shape. For purposes of illustration the rod has been shown as being of hexagonal cross-section, but other non-circular shaped ice cross-sections may be employed with the present invention. The end of the rod 6 is tapered to form a conical portion 7 which terminates in a flat end 8. The drill steel 6 is of greater cross-sectional area than conventional steels, at the initial point ofcontact with the bit which has contributed to increased strength and life of the steel.

An irregular breakout line 9 is formed at the juncture of the conical section 7 and hex section.

Various types of bits may be utilized with the present invention and the bit 10 chosen for illustration is of the type having four integral cutting edges 11.

The bit includes a skirt 12 which defines a tapered socket 13 that terminates in the bottom '14. The tapered socket is complementary to the tapered portion of the rod and forms a leakproof joint that assures the passing of cleansing fluid from the bore 15 of the rod out through the holes 16 in the drill bit. It is preferable to prevent the end of the drill steel 8 from bottoming in the bit. It will be noted that the conical portion 7 of the rod wedges tightly in the bit skirt and therefore does not usually contact the hit bottom 14. This construction provides full circumferential contact and assures that the bit will stay tight on the rod and usually will not be driven thereon to a point Where the rod bottoms in the socket, thus allowing a wide tolerance of dimensions between the socket and rod.

As shown in Figure 2, the end portion 18 of the skirt extends beyond the conical portion 7 of the rod and extends around the hex portion thereof, leaving a space 19 between the hex flats and the skirt.

As the bit is driven onto the rod, the irregular breakout line 9 distributes any stresses in the drill steel and prevents stress concentration therein. In other words, if the irregular breakout line was not provided and instead the tapered portion of the steel was of full circular crosssection throughout the length of the skirt 12, then when the bit was in use, a line of stress would be developed transversely across the steel to cause fracture along this transverse line. However, by providing an irregular breakout line which is formed at the juncture of the conical portion and the hex portion, these stresses are distributed along that length of the steel within the skirt and are not concentrated in any one transverse plane across the steel. The contact section of the skirt contacts the drill steel at the irregular breakout line and distributes the stresses. Only a relatively small conical section of the steel engages the bottom portion of the socket of the bit to give full circular contact,'thus providing a leak-proof joint and assuring cleansing fluid being ported into the bit holes. The bit life will also be increased although the bit is a more expendable item. Experience with these improved drill steels and bit connections has shown a marked reduction in the breakage of these steels and bits that occurred in prior art devices where full circumferential contact for the axial length of the skirt on the rod was provided.

In the manufacture of bits made in accordance with this invention, a straight .60 to .90 carbon steel has proved very satisfactory. The bit is heat treated by heating it to approximately 1400 degrees F. and then quenching only the cut-ting edges to a depth of about one-quarter of an inch. When quenched in a brine solution in this manner, the edges are hardened to 62- 65 Rockwell C. The balance of the bit becomes progressively softer towards the other end. The other end of the bit, that is the annular skirt portion 18, is left soft, at about a Rockwell C of 20, which is a ductile condition that can be deformed and stretched without break- As shown in Figure 3, when a bit made in accordance a he ki be or defama a formation ofthe skirt to the hex shape, the skirt is pre- 3 I a with the above procedure is, driven on the rod, the outer edge 18 of the skirt is deformed to partially follow the shape of the nonrircular cross-section part 'of the rod. The broken line indicates the original circular shape of vent ed from rotating, on the drill rod and a-particularly tight connection'results between the bit and rod. By

' HIQaI IS of this invention, relatively'easy manufacturing tolerances are permissible between the.'parts; breakage of the drill rod connections and the bits has been substantially eliminated; and a fluid tight seal is provided to assure proper of spoil at 'the, bit. i

' Various mo des'of cari ying o'utrthe invention are contemplated as being within the scope of the following claims particularly pointing outand distinctly claiming the subject matter regarded as the invention.

lelai w end is spaced from said non-circular portion whereby stress concentration is minimized due to stress distribution along said breakout" line. i

2. In combinatioia drill rod having a portion of its length of non-circular cross-section, said rod also having a tapered end forming a conical portion, said conical and non-circular portions merging to form an irregular breakout line, rod also having a cleansing fluid bore extending axially therethrough, a drill bit having a skirt portion which defines a tapered socket which extends to terminate at the skirt end, said tapered socket being complementary to said conical portion and forming a sealing fit therewith, said .bit having an aperture extending therethrough for conducting cleansing fluid from said bore through said bit, said skirt extending over at least part of both said non-circular portion and break out line and being spaced from the former whereby stress concentration is minimized.

Due to the, partial d.e;

3. In combination, a drill rod having a portion of its length of non-circular cross-section, said rod also having "a tapered end forming a conical portion, said conical and non-circular portions merging to form an irregular breakout line, a drill bit having an annular skirt portion which defines a tapered socket which extends to terminate at the skirt end, said tapered socket being complementary to' said conical portion and forming a sealing fit therewith, said skirt extending over at least part of both said non-circular portion and breakout line and being' spaced'tromthe former whereby stress concentration is minimizedfsaid skirt portionlbeing sufliciently ductile so as to deforin'over'said non-circular portion without fracture.

4. In combination, a tubular drill rod having a portion of its length of'no n-cir'cular cross-section, said rod also having a tapered end forming a conical portion, said conical and non-circular port-ions merging to form an irregular breakout line, adrill bit having hardened cutting teeth at oneand a portion at the, opposite end which defines a tap ered socket extending therefrom and terminates at the skirt endfsaid tapered socketbeing' complementary to said conical portion and forming a sealing fit therewith, said bit having an aperture for conducting fluid from said rod' through said bit, said skirt having an end portion extending over at least part of both said non-circular portion and breakout line and being spaced from the former whereby stress concen tration in said rod'is' minimized, said end portion being sufficiently ductile to deform around said non circular portion without fracture of'said skirt.

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