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Publication numberUS2325020 A
Publication typeGrant
Publication dateJul 20, 1943
Filing dateMay 3, 1941
Priority dateMay 3, 1941
Publication numberUS 2325020 A, US 2325020A, US-A-2325020, US2325020 A, US2325020A
InventorsAlbert Shaw Markworth
Original AssigneeAlbert Shaw Markworth
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Expansion bit
US 2325020 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

July 20, 1943. M, A, SHAW 2,325,020

' EXPANSION BIT Y Y Filed Ma :5, 1941 hlmurak mmwpqw MIMI-MAW Fatented July 20;

UNITED STAT Markwortl Albert Shaw; Vancouver,

1 Columbia, Canada British I e 1 Application Ma .3, 1 941, SeriaLNo. 391,739

1 Claim. (01. 145 -124) My invention relates to improvements in exdrilling tapered holes in lumber in which dowels and the like are to be secured by fox wedg'ing.

The object of the inventionis to provide-means pansi'on bits, which are particularlyadapted for whereby the holes drilled increase'in diameter progressively from the surface of the material drilled to the bottom of the hole. A further object is to provide a structure wherein the cutting elements are so supported in the drill stock as to prevent chattering, to the end that the walls of the hole are smooth and the grainof the wood free from ragged appearance.

The invention consists of a drill stock in which a pair of cutting elements hingedly connected together at one end are mounted and in which means are provided for moving the cutting elements endwise beyond the end of the stock and for spreading the projecting ends ofsaid elements apart, as will be more fully described in the following specification and shown in the accompanying' drawing, in which Figure 1 is an elevational view of the invention with the cutting elements retracted.

Figure 2 is a part sectional view showing-the cutting elements extended.

In the drawing like characters of reference 1 indicate corresponding parts in each figure The numeral I indicates a drill bit stock which is adapted to be held in a chuck of a drilling The stock 1 is slotted upwardly from 1 machine. its lower extremity 'as at 2 to receive a pair of cutting elements 3. Each of thecutting elements is an elongated strip of steel having a substantially l-shaped outer end 4, one angle of. the 1V being bevelled off and suitably curved in the di-; rection of rotation'to provide a cutting edge Sb Each cutting element is provided intermediate its length with anarcuate slot 6 which extends from about the longitudinal axis 'of the strip downwardly and outwardly towards the cutting edge 5. One side of each cutting elementfis Extending through the stock land the'arcuate 'slots 6 offthe cutting elements is a pin 8. An

elongated slot I0. is 'formed" intermediate the length of the stock l which is transverse to the slot 2 and a' pivot pin. l2 extends through said slot and'the upper ends ofthe cutting elements 3. Theflen'gth-Of the pivot pin I2 is such as to project into an annulargroove I3'which is formed v in a collar 15; The collar l5 is made in any suit able manner to slide freely upon the stock I and permit the stock-to rotate therein, it is provided with trunnions I6 on its periphery which" are adapted to be engaged bya" suitable fee'd lever,

fulcrummed on a stationary part of the drilling j machine.

In operation, the bit is brought down approximately to the face of the work to be drilled and themachine is'set' in motion. The collar IS on being lowered along the stock forces the pivot pin l2 andthe cutting elements 3 downwardly. to project beyond the lower end of the slot 2/ ,The outer ends 4 of the cutting elements are progressively spread apart as the elements descend due to' the curvature of the arcuate slots 6 as their side edges ride downwardly on the pin 8. What I claim as my invention is: An' expanding bit comprising a, stock having a slot extending from its lower end inwardly,

a pair of cutting elements normally housed within the slot and extending therebelow, said elements each having a cutting edge equal tothe width of the stock and said elements being" pivotally con- 'nected adjacent one end Vbya pivot pin, said,

stock having a longitudinal slot transverse to the first. named slot through which thepivot pin extends, means engaging the pivot pin externally of the stock for moving said cutting elecurved as at 1 to prevent binding in the hole;


' ments .to project downwardly beyond the lower end of the stock, and means'for guiding the lower endsof the cutting elements outwardly as they are moved downwardly.


Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2547915 *Jul 28, 1948Apr 3, 1951C G S Lab IncGrooving tool
US2675036 *Apr 21, 1951Apr 13, 1954Nelsen Magnus ORotary cutter head for dovetail groove cutting
US2818753 *Aug 20, 1956Jan 7, 1958Leggett Guy OReverse taper boring tool
US4347768 *Jul 2, 1979Sep 7, 1982Hilti AktiengesellschaftDrilling tool for producing an undercut bore
US4529022 *Jul 22, 1982Jul 16, 1985Jacobson Delbert GCutting tool
US5800148 *Dec 3, 1997Sep 1, 1998Wise; Michael A.Blind-taper hole saw
U.S. Classification82/1.5, 408/147
International ClassificationB23B51/00
Cooperative ClassificationB23B51/0045
European ClassificationB23B51/00D3