USRE3941E - Improvement in screws - Google Patents

Description

,f dnited Sisme @ma eine.

THE NATIONAL SCREW COMPANY, OF HARTFORD, CONNECTICUT, ASSIGNEES OF ELIJAH S. lPIERCE.

Lmm Patent No. 87,198, daad February 23, 1869; msm No. 3,941, dazed April 26, 1ero.

DIVISION B.

IMPRQVEMENT `19N s'cnnws. l

'The Schedule referred to in these 'Letten Patent and making part o! the lame.

To all whom it may concern:

.y Be-it known that ELI'JAH S. PIERCE did invent a certain new and useful Improvements in Tool for Cut ting Screws, and a new ImprovedScreW, as the product therefrom; and to enable others 'skilled in the art to'make-and use the same, we, THE NATIONAL.

SCREW ConrPANY, oi the city and county of Hartford and State of Connecticut, assigneesof the said ELIJAH S. PIERCE, will proceed .to described its construction and advantage, referring to the drawings, iu which the same letters indicate like parts in the figure.

The nature of this invention consists of a screw, having at the end of the core at the commencement of the thread, and at the point of the screw, a conical form, and the intermediate part the form of a low supplemental thread or elevation between the convolu ,tions of the principal threads.

In the accompanying drawings-A Figure 1 shows a horizontal viewY of the screw, be. ing merely an enlarged view ofEigure 5 of the origi@ nal drawing, l y f v h, beingthe conical point, and

o, the supplemental thread. y

The tool isgztstraght steel bar, of the cross-section, having its extremity ground. on" to a proper angle, back. from the edges, toform a cutting-tool, and to such lateral angle that when the tool is iu use, aud held to .the blank in the direction corresponding to the pitch of the `thread, the plane of the said extremity shall lie parallel to the longitudinal axis of the blank.

The sides of the groove and the voutside edges form the thread, and the edges the bottom of the groove.

^ The toolis held to the blank lin such position that the direction of the groove rectiou or'piteh of the thread, and` is moved forward against and' laterally along the screw-blank in the manner usual in screw-cutting and threading-machines.

The advantages of this invention are, the screw is made to enter more easily and hold more firmly than when the bottom of the groove is of a volute form at l the ends of the thread, and cylindrical in the middle.

We believe we has thus shown the nature, construction, and advantage of this invention, so as; to enahle otheis skilledin the art to make and use the same therefrom'.

What we elaim, and desire to secure by Letters Patent, isfv The screw,

THE NATIONAL SCREW CO'., [L s] By' EZRA CLARK, President.

Y Witnesses; K

.Tamiami W. Buss, ALFRED WATKINSON.

shall correspond to the dias shown, combining a conical point to vthe core and a supplemental thread or elevation bev tween the convolutions of the thread proper, all sub- ,Btantially as andforthe purpose set forth.

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