A Spiral Fluted Screw Extractor Set
A spiral screw extractor is itself a coarse-pitched tapered screw thread. They are left-handed, for use on right-handed threads. These screw extractors are high quality by milled technological process and with the sand-blasted surface.
1. The screw is first drilled out to the proper diameter for that extractor.
2. Then the screw extractor is inserted into the hole and turned in the opposite direction, usually using a tap wrench.
3. As the extractor is turned, the flutes on the tool dig into the screw, causing it to lock tightly and withstand the applied torque required to remove the screw.
4. Turn it till the screw is extracted out.
A disadvantage of this tapered screw extractor is that its wedge action tends to expand the drilled hole and thus weakened the screw. This wedging action can lock the screw even more tightly and make it difficult to extract.