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Tips on how to deal with damaged screws.

Summary

Whilst most screws are easily removed, others can be a challenge to the most experienced among us, particularly if the head is damaged.

Safety

Screwdrivers have pointy ends and although not sharp like a knife, they can still cause serious injury if they slip or are misused.

Rescuing damaged screws

If you end up with a damaged screw, perhaps because you didn't press hard enough, then all is not lost. There are still a few options.

But before starting, ask yourself a silly question: were you turning it the right way? Of course you know that you turn a screw anticlockwise to undo it - you're not stupid. But just occasionally you'll find a left handed screw which turns the other way, most usually on a rotating shaft where the direction of rotation might otherwise cause the screw to come loose. A screw holding a fan, an impeller or a pulley on the end of the shaft of an electric motor might have a left handed thread for this reason.

Small screws in electronic equipment are probably the hardest since there is very little undamaged metal to play with. This iFixit guide covers most of the options, which are summarised below:

• First of all, make sure you're using the right type and size of screwdriver, in particular, Phillips for a Phillips screw or Pozidriv for a Pozidriv screw.
• If the screw head is too badly damaged for the correct screwdriver to work, you can try different one, such as a larger size of a flat bladed one.
• Place a wide rubber band over the screw head and apply the screwdriver to the screw head trough this to get extra grip.
• If sufficient of the head is accessible you may be able to grip it with pliers.
• Add a drop of superglue to the screw head, insert the screwdriver and hold it steady while the glue sets, then try turning it.
• Using a dremel, cut a slot in the screw head and use a flat bladed screwdriver

With larger screws there are a few more possibilities:

• Drill a hole in the screw head and insert a screw extractor. This has a left handed tapered thread in hardened steel which you screw anticlockwise into the hole. Provided you can get it to grip the screw head this will do the job if anything will - but the screw head may shear off.
• Find the largest screwdriver whose tip will reach the bottom of the recess in the screw head. Then fill the recess in the screw head with steel reinforced epoxy. As it just begins to harden and loose its stickiness, carefully press the screwdriver tip into the epoxy to form an indentation exactly matching the screwdriver, then leave it to fully harden before trying again with the same screwdriver.
• If the thread is rusted, then apply a little penetrating oil to ease it, and leave it to soak in. For this, most people immediately think of WD40 but there are many discussion threads on the Internet suggesting that PB Blaster is much better.
• Heat from a butane blow torch may also help in the case of a badly corroded screw, provided this won't damage other parts.
• Tapping it with a hammer may help break up any rust after applying either or both of the two previous suggestions.

Whatever method you choose, you may simply end up with the screw head shearing off, which may allow you to dismantle whatever it was but may then leave you with another problem.