USRE3733E - Improvement in expansive bits - Google Patents

Description

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WILLIAM A. CLARK, OF WOODBRIDGIC, (10th?EUTICUTi Letters Patent No. 20,192, dated May 11, 1858; reissue N 3,516, dated June 2Q, 1869; reissue No. 3,733, dated November 16, 1869.

IMPROVEMENT IN EXPANSIVE BITS.

The Schedule referred to in these Letters Patent and making part of the same.

To whoml it may concern:

Be it known that I, WILLIAM A. CLARK, of Woodbridge, in the county of' New Haven, and State of' Connecticut, have invented a new Improvement in Expansive Bits; and I do hereby declare the following to be a full, clear, and exact description of the saine, reference being had to the 'accompanying drawings, in whichj Y Figure 1 is a side view of an expansive bit, embodying a portion of my improvements; v. Y

Figure 2, an opposite side view; y

Figure 3, au clevatiornits, plane of projection being transverse to figs. 1 and 2;

Figure 4, a sectional elevation, its plane of projection being parallel to that in iig. 3, but transverse to that in iigs. 1 and 2,.

Figure 5, a side elevation of the. movable cutter;

Figure (i, a reverse view oi it;

Figure 7, `au end elevation;

Figure S, an inverted plan, or, in other words, an under-side view;

Figure 9, a backside elevation of a cutter so madel as to always keep the movable cutter at just the same distance behind the point of the bit, while Aat the sa'me time the depth of wood left to support the central portion of the bit is varied by the adjustment of` said cutter;

Figure 10, a. side elevation of abit, which, while embodying the same novel features as represented in the previous iignres, is also so formed as to throw the chips in front of the movable cutter, which arrangement avoids the necessity of filing away the backside ofthe bit toallow the chips to pass;

Figure 11, an elevation'transverse to ti". 10;

Figure 12, a backside eleration of the same bit; and 'in Figure 13, a vertical section, showing the same movable cutter secured-in the saine way in a mortise, instead of a recess in the body ofthe bit.

This in'vention relates to an impriwen'ient in what are known as expansive bits, that is, bits constructed with an adjustment whereby the cutter may be extended or contracted so as to cut a larger Aor smaller hole, as the oase may be; and

The invention may be stated in general to consist of au expansive bit composed of' a recessed shank, into which the adjustable or expanding cutter is fitted, and in which it is adj usted and held, substantially hereinafter described. A

To enable others to fully understand my invention, I will proceed to describe the same as illustrated in the accompanying drawings.

A is the shank ofthe bit, upon which the inner or stationary cutter is formed, and in which the recess or mortise is made, which receives the movable cutter B. The construction of' the main portion of' the shank, and of' the. cutting-lip permanently attached to it, is very much the same as those of other expansive bits, but the mode of securing the movable cutter B in its place is different. v v

In order to provide forthe securing of the movable cutter B, Iform an open recess in my bit, from' thc bottom of vwhich rises a V-sha-pcd ledge, a, so as to receive the V-shapcd groove b in the said movable cutter. The forin ot' the ledge c and that of the 'groove b is shown in figs. 3, 4, 11, and 13. lhe form of the groove is also shown in fic. 7. The form of thcgroove b, and ofthe ledge upon which it rests, is suoli as to give a firm bearing to the cutter B, and draw it snugly against the-hack ofthe recess when the pressure is applied, which secures the said cutter in place.

Y The cutter, when thus dovetailed into the shank at its lower end, is secured in place withgreat ease, and without danger of injuring its 'cutting-edge, which is entirely relieved from any injurious pressure and contact with the shank, by reason of thc dovetail connection between the shank and the lower end ofthe cutter, this connection also serving to' bind that end ol'v the cutter most firmly and tightly to the shank.

In order t0 secure the cutter, I employ a bevelled plate or follower, I), driven homo by a screw, E, in such manner as to press the cutter B against the backside and bottom of the recess in which it is secured, the said cutter being also bevelled, as shown, to facilitate the accomplishment of this purpose.

The form and arrangemei'it of these parts areshown in figs. 1, 3, 4, 10, 11, and 13. In thc first four figures, the relative positions ot' the cutters are such as to deliver the chips from the stationary cutter C upon the backside of' that part of' the stock which supports the movable cutter, and this involves the necessity of cutting away the stock, as shown at c in figs. 2 and 3, to allow the chips to pass. This, of course, weakens that part of the stock, and makes it necessary to secure suficieut strength by retaining more metal on the side upon which the cutter B is attached, and, as a consequence, the edge of this cutter is thrown out too far from the centre oi' thestock, and its efciency of operation in different positions is thereby reduced. To obviate this ditiiculty, I form the stationary lip C in that position upon the stock in which it is represented in figs. 10, ll, 12,' and'l, by which arrangement the chips from it are delivered upon that side of the stock which is cut away to receive the cutter B, which allows the opposite side to be left entire, and also so balances the operating-parts as to relieve tli'e screw J from a portion of the pressure which would otherwise be thrown upon it when in operation.

This arrangement enables me to bring the edge of the cutter 'B nearly back to the centre of the stock, as shown in iig. 11, and, in large bits,it may be brought further back than it is there represented as being placed.

It may Vin some cases be considered desirable, in the construction of very large bits, to leave a portion oi' metal in front of the cutter B, :ts-shown in iig. 13, for the more eifectual support of that side ofthe bit. In this case the screw E should extend through this part, as shown.

The mode which I have above described of supporting and securing the cutter B, supports it without its resting ou the cutting-edge, arid in my construction, space is left under the cutting-edge, as shown; and by thus supporting it, the edge of a large cutter may be set higher in the stock than it is .necessary or best to set the edge of a small one, which allows-more wood to be left near the stock, to support it where a large cutter is used. The cutting-edge of the cutter B is inciinedso as to bring its working-end lower than the other, for the twofold purpose ot' causing the unem.

ployed end to clear the wood, and of leaving a portion of vthe wood around the central portion of the bit-to support it, while at the saine time the outer end of' the cutter B shall cut nearly or quite as far in advance as the inner cutter. The seat upon which the movable cutter rests at the bottom, has, iu most expansive bits, an inclination corresponding with that vof the edge of the said cutter', and this feature isrel tained in my bit, as represented in all the drawings except fig. 9. When so constructed, the sliding of the movable cutter outward, also carries its workingend' downward, so that when placed `in its 'extreme outward position, it will cut considerably deeper than when withdrawn so as to cnt its minimum hole. It is desirable, however, that the depth it will ont shall be as nearly equal as possible; and further, it becomes necessary, when-the movable cutter is required to cut away a very large amount of wood, to preserve a considerable shoulder of the wood adjacent to the stock, for its support against the strain imposed upon it by the resistance against the movable cutter. For this purpose I make my longer cutters so that the edge shall stand a little higher in the stock than the edges of those which are intended to cut a smaller hole, which my mode of supporting the cutters upon a ledge or shoulder, placed aboveY the edge, enables me to do; and this provision for giving the proper shoulder and depth of cut, answers very 'satisfactorily for most purposes.

Should greater nicety in these respects be desirable, it may be attained by the adoption of the cutter shown in fig. 9', and the' use of a horizontal V in the stock, as in this'case the edge of the cutter is inclined with reference to the groove b, while in the cutters shown in the previous iigures it is parallel to it. This arrangement causes the point of the movable cutter tovalways work at v-the same depth, and makes the depth of the shoulder in exact proportion to the disL tance at which the point oi' the cutter is set -from the centre.

Bits with movable cutters secured in a mortise in the shank or stock, have been long known, but the modes which have been adopted for securing these cutters have been more or less objectionable, so much so as to interfere with their general use. One objection is that the bit, or more properly the movable cutter, being secured by being'keyed down upon the bottom of the mort-isc, the cutting-edge of this movable cutter rests upon the middle of the stock, 'which not only destroys thecutting-edge of wood-boring tools, but also precludes such anarrangement as would allow a greater depth of wood to be left contiguous to the central cutter or stock, to support it when alarger cutter is put in, or a larger hole bored, which requires such support for the stock. Y'lhese objections are entirely overcome by my invention.

Having fully described my invention,

That I claim as new and useful, andl desire to secure by Letters Patent, is-

1.A The formation of a V-ledge in therecessed shank, and a correspondingly-shaped recess in the adjustable cutter, back ot' or above its cntting-edge,"to tit the ledge in the shank, substantially as and for the purposes set forth.

2. The combination, with the recessed shank and adj ustable cutter in which a V-ledge and correspondinglyshaped recess are respeetivel y formed, as speciiied, of the follower and screwfor driving'hoine the cutter againstthc said V-ledge, which forms its lower bearing, and binds it to .the shank, substantially as shown and set forth.

In testimony whereof, I have here signed my name, in presence of two subscribing'witnesses.

Witnesses: WM. A. CLARK.

M. BAILEY, W. H. MCGABE.

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