Global Fastener News

1994 FIN – Taylor’s Most Frequently Asked Fastener Questions

May 20
00:00 2010

 

November 28, 1994 FIN – Jim Taylor, vice president of Elmhurst, Illinois-based Semblex Corporation, told the Southeastern Fastener Association fall meeting in Charlotte, NC, that in comparison to machine screws and thread cutting screws in a pilot hole, the advantages of thread-rolling include the largest shear area, greater resistance to vibration loosening, stronger mating threads with uninterrupted grain flow; extra strength from work-hardening method of forming; stronger fastening; and 65% engagement.
A machine screw has 75% thread engagement; the tapped pilot hole with cut threads shows weakening by interrupted grain flow; chamber depth and chip space are needed in a tapped hole; the area is subject to shearing; and tolerances required on the male and female threads contribute to looseness; Taylor said.

The thread-cutting screw requires a longer point; the tapped hole with cut threads show weakening by interrupted grain flow; the unsymmetrical point contributes to difficult starting and re-use; and champfer depth and chip space are needed in the tapped hole.

Taylor’s list of the most frequently asked questions and his answers:

• What is the unique shape of the thread-rolling screw?
Trilobular.

• What are the benefits of this shape?
(A) Will produce higher percentage thread engagement;
(B) Produces prevailing torque, which helps prevent screw loosening;
(C) Produces resistance to loosening caused by vibration in assemblies.

• What are the advantages of “thread-forming” with thread-rolling screws?
(A) Cold-formed exactly fir internal threads;
(B) Internal threads are formed to tap dimensions;
(C) Formed threads are stronger due to the “work-hardening” effect and uninterrupted grain flow;
(D) No chips, no burrs.

• Why do thread-rolling screws provide stronger assemblies?
(A) High resistance to stripping
(B) Tensile strength of 135,000 PSI;
(C) Increased thread depth allows higher tensile loading of the assembly.

• What advantages do the thread-rolling screws bring to the production line?
(A) Low driving torque;
(B) Excellent drive-to-strip ratio to aid in power driving of fasteners;
(C) Overwhelmingly reduces fastener installation costs;
(D) No chips, no cleaning.
©1994/2010 Fastener Industry News

Related Articles

0 Comments

No Comments Yet!

There are no comments at the moment, do you want to add one?

Write a comment

Only registered users can comment.

Register for our Mailing List

Sign up now to receive valuable weekly news about the fastener companies, people, and trends impacting the industry. REGISTER NOW
error: Content is protected !!