Tool Techniques: Impact drivers demystified

Image courtesy of Morguefile
Date:1 June 2010 Tags:

Stuck fasteners are a mechanic’s worst nightmare. Nothing’s more infuriating than spending an entire afternoon trying to remove a single Phillips head.

Immovable hex bolts are tough enough – but Phillips-head screws are way too easy to strip. Most of the effort goes into trying to keep the screwdriver seated in the head. Tapping the screwdriver handle will help seat the bit, but it will still come out if you twist hard enough. And there’s a chance the blows could break the handle in your hands.

The best way is to use a handheld impact driver. This tool has internal cams that spin the bit when you whack the handle with a hammer. Start by engaging the driver’s bit to the screw. Firmly tap the end a few times to seat the bit. Then slowly rotate the handle in the direction you want to move the screw – in this case, counterclockwise – until it stops. Now carefully hold the handle and strike it hard. The device rotates the screw while the hammer blow keeps the bit seated. The impact also loosens up any crud cementing the fastener. Alternate loosening with tightening, and eventually almost any Phillips screw will budge. Unfortunately, this will only work on 6 mm or smaller fasteners.

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