Dies for making thread-forming screw with step taper

Details Dies for making thread-forming screw with step taper Dies for making thread-forming screw with step taper

1979-06-07

1981-03-17

Mehr, Milton S.

Metal deforming

Tool and/or tool holder

Tool-comprising die plate having ribs and/or grooves

B21H 306

Patent

active

042559596

ABSTRACT:
A thread-forming screw has a point or lead thread portion having a relatively steep entry angle with respect to the screw axis. Adjacent to the point thread is a tapered thread portion of about two to three pitches in axial length. This tapered thread has a shallow entry angle defined by the taper of the maximum diameter of the thread toward the point. This shallow entry angle may be approximately 5.degree. to 8.degree. or equal to about three times the helix angle of the tapered thread. This configuration of the tapered thread results in a balanced action of thread formation and axial in-feed of the screw, resulting in a lower end pressure to initiate the thread-forming in a workpiece. A roll-threading die is contoured to provide ridges and valleys to effect the tapered thread portion.

REFERENCES:
patent: 2183688 (1939-12-01), Olson
patent: 2348850 (1944-05-01), Richards
patent: 3246556 (1966-04-01), Phipard, Jr.

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