US98943A - Improved screw-tap - Google Patents

Description

Cd'thttetl 5mm @met @time Letters Patent No. 98,943, (lated January 18, 1870.

IMPROVED SCREW-TAP.

The Schedule referred to in these Lettere Patent and making part of the name.

To all whom it may concern;v4

Be it known that I, CHRISTIAN L. FEHRENSEN, of the city, county, and State of New York, have invented a new and improved Screw-Tap; and I do hereby declarethe following to be a full, clear, and exact description thereof, which will enable those skilled iri the art to make, and use the same, reference being had to the accompanying drawing, forming partof this specilioation, iu which drawing- Figure 1 represents a front view of this invention.

Figure 2 is a longitudinal section thereof'.

`Similar letters indicate corresponding parts.

This invent-ion relates to a screw-tap, provided with a single dat face, cut down` at its deepest place to the centre (or nearly so) of the tap, and .ruiming up in a gradual curve to the circumference of said tap, in combinat-ion with a round guiding-nipple, formed bythe body of the tap, between its tapering end and the flat face, in such a manner, that by said fiat face two sharp cutting-edges are' produced, and that a single tap is suilcient to'cut a-deep and perfect thread, said tap being held in lthe proper position, at the commencement of the operation, by the guiding-nipples.

The letter A designates a screw-tap, vwhich is made tapering toward. its end a, so that` on said end the screw-threadis eutirelycut away, while on the upper part of said tap the thread is left intact, as shown.

Said tap is provided with a single at face, @which is cut down to the centre of the tap, or nearly so, and

runs up in a gradual curve to the circumference thereof, as seen in the drawing, so that two sharp cutting-V edges, c, are produced,`which materially assist in forming the thread in the nut to be tapped.

That portion of the tap below the at face is left round, `so as to form a guiding-nipple, d, which serves to keep the tap in the proper position at the commencement of the operation.

l By these means a screw-tap is obtained, which allows of cutting a perfect thread by a single operation, while with taps of the usual construction two or three different taps are required to obtain the desired result. It is obvious that my improvement is applicable to taps with at threads, as well as to such with V- shaped threads.

What 1 claim as new, and desire to `secure by Let-y

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