Impact wrench

Q I would welcome your advice please on when not to use an impact wrench to undo stubborn fasteners. A couple of years ago, with my 70th birthday approaching and getting more weak and feeble, I purchased an 18-volt Dewalt impact wrench as I look after four aging cars in my family. The wrench is brilliant. It takes the effort out of much of the work, but I worry about when not to use it.

Many online mechanics use wrenches all the time but others advise against, eg. they use breaker bars on bolts securing subframes to the body – is that because of the risk of the shock loosening captive nuts? Also many say don’t use impact wrenches on wheel hubs because the shock could damage ABS sensors and don’t use them on nuts that are fastened to studs bonded into rubber etc. (eg. suspension top mounts), for fear of shearing the bond.

I look forward to your advice.

Keith Gibson

A The use of an impact wrench is discretionary, but I would say that in most cases the impact wrench can be used to remove any fixing. There may be problems with captive nuts as you mention, and in these cases then a slow application of pressure using a breaker bar is the best option.

Undoing wheel nuts should not pose any difficulty for the impact wrench, and I would note that if it does, then a problem would still be present if a breaker bar were used.

The golden rule is not to tighten fixings up using an impact wrench, as this would be where problems and damage could occur.

One other point to mention is that ordinary sockets are incompatible with impact wrenches, and only dedicated impact wrench sockets should be used to ensure that the cyclic hammering loads are within the sockets capabilities. Under these conditions ordinary sockets may fracture and splinter.