Maintaining thread strength in low shear strength materials

08 February 2010

The increasing use of aluminium, other exotic alloys and engineering plastics throughout industry poses the problem of maintaining the highest possible thread strength within inherently low shear strength materials. HeliCoil, which is able to introduce a high-tech thread within lower-strength parent materials and to replace damaged or worn threads, is one answer to that problem.

Helicoil products are supplied exclusively in the UK by Bollhoff Fastenings, which will be exhibiting the full Helicoil range at Southern Manufacturing (February 10-11 2010, FIVE, Farnborough), including the new HeliCoilplus.
With the Helicoil system, the first coil is reduced in diameter, to form a ‘lead-in’ feature while the outer profile of the insert is simply wound into the mating thread with a mandrel, resulting in a true-to-gauge internal thread. After fitting, it has the tolerance of 2B or 3B, in accordance with NASM 33537.

Screw-locking is another product option where the thread locking function is achieved by one of several polygon formed coils gripping the installed screw. In this way an elastically resilient friction lock is created and this eliminates the need for secondary adhesives.