New level of threaded fastener security
12 June 2018
Bollhoff’s Helicoil Plus range of threaded inserts has been developed to provide design engineers with additional security when using threaded fasteners in critical environments, particularly where loosening fasteners are at best an annoyance and at worst a potentially catastrophic occurrence
The new range has proved especially resilient in applications such as electric motor and factory automation systems where both low and high frequency vibration – especially over the long term - can threaten the integrity of an installation. Moreover, as new materials and combinations of materials continue to emerge, an additional advantage of the new Helicoil Plus range is reported to be its ability to cope with thermal expansion and contraction far better than ‘normal’ threaded inserts are able to, rendering them ideal for use where both vibration and heat variations occur simultaneously. This has proved valuable to design teams working on projects that join materials with different rates of thermal expansion and contraction.
The new level of threaded fastener security provided by Helicoil Plus is a direct result of the key design element in the insert, a patented feature of the range. Whereas a Classic Helicoil threaded insert is sized larger than the tapped hole, the development that is unique to Helicoil Plus and the factor – and patent – which sets it apart from all other threaded inserts is the altered profile of the first thread. Bollhoff’s Clive Brown explains: "As it is only this first thread which ‘leads’ the Helicoil Plus insert into the hole, the remaining part of it which follows finds itself under significant and equalised radial compression inside the host material. This delivers reliable, repeatable and dependable threaded fastener security with industry-leading pull-out resistance."
In effect, as the Helicoil Plus insert is led into the hole by the patented profile of the initial thread, the remainder of the insert body is ‘deceived’ into following and thus squeezes itself into the hole extremely tightly. The result is significantly greater resistance to ‘pull-out’ compared to other threaded inserts, irrespective of the host material type, plus a greater assurance of long term integrity to designers.
Additional locking feature
In addition to these advantages, Helicoil Plus inserts can also be specified ‘off the shelf’ with a mechanical locking function which delivers even greater threaded fastener security. Whereas the standard product is free-running and features precision formed rhombic profiles to both sides which result in an internal thread that is true to size along its entire length, the Screwlock version goes further by providing design engineers with an additional and inbuilt positive mechanical locking facility.
On the Screwlock Helicoil Plus, an integrated screw locking function featuring one or more polygonal threads is designed into the insert. This results in an elastically-resilient friction locking function which Bollhoff states was developed for ‘critical use’ applications in mind, and those environments where continued vibration has the potential to cause loosening of threaded fasteners.
Brown continued: "With modern drive systems and automation equipment able to run faultlessly for thousands of hours it became apparent that in some applications it was the fasteners or the machine mountings that could present challenges and problems in service, leading to significant downtime and cost in some cases. In many of these instances it is the presence of continued residual vibration which was sometimes allowing threaded fasteners to work loose, with obvious negative consequences.
"By designing-in the Screwlock version of Helicoil Plus, engineers now have an opportunity to specify something which has proved to be a real problem solver in these circumstances. Because the positive locking facility is part of the threaded insert, the use of additional locking devices such as washers, lock nuts and threadlockers has proved to be unnecessary. So by being able to talk to design engineers in the early stages of a project we can help to deliver a better engineered solution – one which lasts for the long term and is 100% maintenance free - from the outset."
- New threaded insert range resilient in applications where low and high frequency vibration can threaten integrity of installation
- The level of threaded fastener security provided by Helicoil Plus is a direct result of the key design element in the insert
- Inserts can also be specified ‘off the shelf’ with a mechanical locking function which delivers even greater fastener security