US 2179689 A
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|. L. EARNHEART 2,179,689
DRILL BIT Filed 7 July 28, 1937 Zhwentor Patented Nov. 14, 19 39 I UNITED STATES PATENT OFFICE DRILL BIT Isaac Earnheart, Troy, Mont. Application July 28, 1937, Serial No. 156,160
a 1 Clam.
My present invention relates to improvements in drill bits for uswithpower machines or tools in earth boring. The bit of my invention is especially designed forsinking holes in rocks etc., It as in mining operations, and the bitis employed with an impact or endwise-concussion type of drilling machine-tool having a rotary feed, and water passages for conveying water to the cutters or cutting edges, and for conveying-water and W debris from the cutting edges ofthe bit.
In carrying out my invention I provide a bit which is readily detachable from its shank, drill-bar, or drill-stem, in order that the bit may be removed when necessary for sharpening; and w the cutting edges or cutters of the bit are fashioned witha bevel-face, and a longitudinally extending front face forming part of a rearwardly extending notch, which facilitates sharpening and ire-sharpening of the cutters or cutting edges. my These bevel-end-faces of the cutters may repeatedly be ground down or sharpened, and in conjunction with the recess and the front longitudinal face of the cutter, each cutter may with facility be ground a number of times'for re- 25 sharpening, thereby increasing the durability of a drill bit, and securing a maximum service for a bit.
The plural cutting edges of the bit arearranged tangentially of the center-hole andin 30 parallel pairs, perpendicular in their relation to the axis of the bit, and these sharp cutting edges, under repeated impacts or end-concussions of the machine-tool, and the rotary feed of the bit, chipofi the rock, rather than'dig into the rock, 35 thereby reducing the strain onthe cutting edges or cutters, increasing the cutting speed of. the
bit, and-facilitating both the impact and the rotary-feed operations of the machine tool. The
rock thus chipped. ofl forms a debris that may readily be conveyed from the cutting edges, and
the flowing water clears away such debris from the cutters. I L The invention consists in certain novel combinations and arrangements of parts involving the 51 parallel pairs of tangentially oifset cutting edges,
the front longitudinally extending faces' and the bevel-end faces of the. cutters as will hereinafter be more fully set forth and claimed. In accompanying drawing I have illustrated one complete 50 embodimentof my invention wherein the parts are combined and arranged according to modes I have thus far devised for the practical application of the principles of my invention, and it will be understood that changes and alterations W may be made in this exemplifying drawing, withoffset, parallel, cutting edges.
in the scope of my claim, without departing from I the principles of my invention.
Figure 1 is a, plan view of the impact or concussion face of the bit, showing the arrangement of two pairs of bevel-edge, or chisel-putters of the bit.
Figure 2 is a side view of the bit showing it. threaded to the reduced threaded end of a tool shank, stem, or drill bar. v
Figure 3 is a perspective View showing the four cutters, with their bevel faces and frontlongitudinal faces.
' Figure 4 is a transverse sectional detail view of the bit at line ti of Figure 2. a
Figure 5 and Figure 6 are side views of a modified form of the bit with one pair of tangentially In the assembly view of Figure 2 a well known type of drill-rod, stem, or shank i, for a machine tool, is shown with its central water passage 2 ex- 20. --tendi ng longitudinally therethrough, and this stem has a reduced, threaded head 3 upon which the bit t is detachably mounted. The bit, in the form of a cylinder, is'fashioned with a threaded socket ii to fit over the head 3, and it is also fashionedwith a central water passage or duct 5 forming an extension of the passage 2 for supplying water to the cutters, and for conveying the water and debris to the rear as the cutting progresses. g 1
The shank l forms part of an impactor concussion tool that is provided with a rotary feed for the shank and bit, and thesemembers are slowly rotated as the tool shank and bit are quickly agitated or reciprocated.
The impact end of the bit swells or ,flares out to form a diametrically enlarged bit-head 8, and
the impact face of this head is fashioned with a plurality of cutting edges in diametrically-offset pairs that radiate from the central opening or $0 duct 6. In Figure l'it will be seen that the cutting edges 9, II], II, and I2 are" arranged in tangentially-oifset parallel cutters or cutting edges 9|I and 'I0l2, which are in advance of the rehiainder of the bit, and these sharp edges, by
faces l5 of the cutters. These notches also provide clearance for the sharpening operations of the cutters, and the bevel faces l5 are ground downby a suitable machine tool, to form the sharp cutting edges. Thus the length of the straight, flat front faces l3 of the bit-head, and the bevel-edge or face l5, permit of re-sharpening thecutters with facility, and the repeated sharpening operations prolong the life of the culty is usually met in sinking a perfect cylindrical hole.
When the bit, is penetrating a rock having a crevice at the side ofa hole, and four cutting edges are employed as in Figure 1, it will be apparent thatthe work is uniformly distributed to three of the cutters, while the four cutter is passing through the crevice, thus equalizing the impact by distributing the work of three of the cutters to stabilize the performance of the bit.
In Figures 5 and 6 the bit is designed for use with a single pair of tangentially-ofiset cutting edges or cutters l0 and I2 instead of the two pairsused'in' Figure 1, and this type of cutter is adapted for a variety of uses where conditions are met dissimilar to those encountered by the bit of Figure 1.
Having thus fully described my invention, what I-claim as new and desire to secure by Letters Patent is:
In a drill bithaving. an enlarged head and a centrallongitudinal water passage therein, said bit comprising four cruciform cutters having rearwardly extending longitudinal notches between adjoining cutters, each cutter having a tangentially arranged cutting edge with its inner end terminating at the water passage, said cutting edges being arranged in coplanar pairs at opposite sides of the'water passage, rearwardly beveled end faces on the cutters, said notches each being formed bya fiat front face on one cutter and a rearwardly curved face on an adjoining cutter, and said notches diminishing in area from the cutting edges and each merging at a point in'the periphery of the head.
ISAAC L. EARNHEARTr