Impact Wrenches Statement

Further to a previous statement made by the NASC in 2012, the confederation has received an increasing number of enquiries regarding its stance on the use of impact wrenches during erection/dismantling and alterations to scaffolding.

In order to provide clarity and advice for members and other users of impact wrenches, the NASC has recently completed some testing. A wide range of drop forged couplers from different suppliers in various conditions (new, used, lubricated and unlubricated) were tightened using two popular types of impact wrenches as well as a traditional scaffolding spanner. In excess of 60 tests were completed.

The subsequent results data indicated that there were no concerns or adverse effects in respect of any of the tests carried out (for both impact wrenches and traditional scaffold spanner). It is therefore the view of the confederation that the use of impact wrenches during erection/dismantling and alterations to scaffolding is acceptable. However there are several important recommendations which should be considered by the employer prior to authorising the use of impact wrenches by employees:

  • The recommended force required to tighten a fitting is 50 N/mtr as stated in EN 74. Most wrenches have stated torque settings (N/mtr) in excess of this recommended figure. However during testing it was noted that settings published by the manufacturer can differ greatly from what is actually achieved. It is therefore recommended that any employer considering authorising the use of impact wrenches carries out testing to establish that the impact wrench which they intend to authorise for use by their employees is capable of applying the correct torque to scaffold fittings on a consistent and recurring basis. Further to completion of an adequate risk assessment by the employer the impact wrench may then be deemed fit for purpose for erection/dismantling and alterations to scaffolding by their employees.
  • It is recommended that prior to use of an impact wrench on site the employee should first undergo a suitable period of training, familiarisation and monitoring, to ensure that the impact wrench is being used in the correct manner at all times.
  • The NASC recognises that impact wrenches can offer certain benefits. However members and users of such equipment should be aware that there is potential for concern regarding use and operation. Employers should adequately assess the risk for their own particular situation and ensure that they put in place protocols to cover safe use. It is recommended that any assessment should also address noise and hand/arm vibration.
  • In addition to the initial training and familiarisation phases, it is recommended that employers should carry out regular toolbox talks refreshing operatives with company policy and rules for the safe use of impact wrenches.
  • In the event that a nut is stripped off the ‘T’ bolt it is recommended that the fitting should be returned to the employer’s yard where a new replacement ensemble (‘T’ bolt, nut & washer) can be fitted by the company’s maintenance team.
  • Impact wrenches are normally supplied with rechargeable lithium batteries that provide a more stable power pack. However the confederation recommends that all users follow manufacturer’s instructions and that battery life should be monitored.
  • This statement only applies to drop forged scaffold fittings. The NASC does not recommend the use of impact wrenches with ‘pressed’ type scaffold fittings.

The NASC has developed a basic Tool Box Talk which members and other users of impact wrenches may find useful.

The NASC will continue to monitor the situation and will issue further information if required.



New £1M Scottish CISRS Scaffolding Training Centre Opens


New NASC Promotional Film Launches


CISRS Instructors Conference Success