The negative effects of using impact tooling in conjunction with TEK® screws.

Ryan Murphy, Technical Director, Evolution Fasteners UK Ltd.

Thursday 28^th November 2019.

The use of impact tooling is prevalent through the construction industry, which is propagated by the fact they are generally included free with other power tools and thus have a high incidence over the correct tooling for use with TEK Screws®[1].  It is our firm belief that from training and awareness: users will learn that the correct tooling and installation procedures will significantly reduce fastener wastage, improve their installation time and form an appreciation for the underlying science and mechanics of TEK Screws®.

For the avoidance of doubt, impact tooling includes (but is not limited to) drill drivers, combi-drills, hammer-drills, impact screwdrivers and impact wrenches.  The difference between these tools are the method of imparting the impact and magnitude of impact.  This then comes back to simple physics: the more energy put into a system, the more heat and mechanical work (work being the product of force and displacement) is done:

1. Additional axial load causes damage (crushing) to self-drilling point (loss of self-drilling performance),
2. Additional axial load causes damage (blunting) to male tapping threads (loss of tapping performance and loss of mechanical performance),
3. Additional torque load causes damage (pre-loading) to screw head (loss of mechanical performance),
4. Combined axial and torque loads cause abrasion of the coating by excessive chipping against the female cut threads (loss of corrosion resistance and loss of mechanical performance),
5. Additional mechanical work and additional heat energy causes ablation of the coating (loss of corrosion resistance and loss of mechanical performance),
6. Additional mechanical work and additional heat energy causes softening (annealing) of the screw (loss of self-drilling performance and loss of mechanical performance).

Ultimately the use of impact tooling is leading to loss of performance and loss of lifespan of TEK Screws® and the use of such tooling invalidates the Evolution® Product Warranty, as well as many other system manufacturers warranties, such as Kingspan® in their Technical Update EU105.  It is also widely condemned by manufacturers and trade associations such as the NFRC® (National Federation of Roofing Contractors) in their GN-01 publication.

It is recommended that TEK Screws® are always installed with metal construction screwdrivers, such as those approved in Evolution’s Qualified Vendor List as well as adhere to the installation instructions, which are included in our Engineering Specification documents for the product you are using.  These are available from our website, alternatively, for further information please call us directly on +44 (0) 141 647 7100 or by e-mail.

[1] “TEK Screw” and “TEK Screws” are registered trademarks of Evolution Fasteners (UK) Ltd.

Photograph credit – Bidvine®, 2019.