Spiral flute extractors can be used to remove a screw with a damaged (stripped) slot, as well as a screw with a broken-off head. They get their name from the spiral flute on the tapered end, see photo.
These extractors work by driving the end into a hole drilled in the damaged screw. Then the extractor is backed out — taking the screw with it, see drawings below.
undamaged screw hole. The advantage to using a spiral flute extractor is that you can get the screw out without damaging the screw hole. So you can immediately replace the screw with a new one.
drawbacks. Unfortunately, these extractors can only be used on No. 8 and larger screws. This limits their usefulness in wood or damaged screw is to use a screw extractor.
working where smaller screws are commonly used. (Each extractor removes just one size screw. They're usually sold as a set of different sizes, see Sources, page 31.)
Another possible drawback is the need to drill a pilot hole. If the head of a screw is broken off, it can be hard to start a pilot hole.
Also, many screws on the market today are made of hardened steel. It's nearly impossible to drill a hole in a hardened steel screw, such as a drywall screw. So, in this case, there's another system you can use.
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