A screw extractor held in a tap wrench A screw extractor is a

tool A tool is an object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many animals use simple tools, only human beings, whose use of stone tools dates ba ...

for removing broken or seized

screw A screw and a bolt (see '' Differentiation between bolt and screw'' below) are similar types of fastener typically made of metal and characterized by a helical ridge, called a ''male thread'' (external thread). Screws and bolts are used to fa ...

s. There are two types: one has a spiral flute structure, commonly called an easy out after the

trademark A trademark (also written trade mark or trade-mark) is a type of intellectual property consisting of a recognizable sign, design, or expression that identifies products or services from a particular source and distinguishes them from others ...

ed name ''EZ-Out''; the other has a straight flute structure. Screw extractors are intentionally made of

hard Hard may refer to: * Hardness, resistance of physical materials to deformation or fracture * Hard water, water with high mineral content Arts and entertainment * ''Hard'' (TV series), a French TV series * Hard (band), a Hungarian hard rock supe ...

brittle A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Bre ...

steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...

, and, if too much torque is applied, can break off inside the screw that is being removed.

Types

left, Spiral flute screw extractors A spiral screw extractor is itself a coarse-pitched tapered screw thread. They are generally

left-handed In human biology, handedness is an individual's preferential use of one hand, known as the dominant hand, due to it being stronger, faster or more dextrous. The other hand, comparatively often the weaker, less dextrous or simply less subjecti ...

, for use on right-handed threads, though there are right-handed extractors for removing left-handed screws. The screw is first

drill A drill is a tool used for making round holes or driving fasteners. It is fitted with a bit, either a drill or driverchuck. Hand-operated types are dramatically decreasing in popularity and cordless battery-powered ones proliferating due to ...

ed out to the proper diameter for that extractor. The extractor is then inserted into this hole and turned in the direction opposing the stuck screw's original one, usually using a

tap wrench A tap wrench is a hand tool used to turn taps or other small tools, such as hand reamers and screw extractors. Types There are two main types of tap wrenches: ''double-end adjustable wrenches'' and ''T-handle wrenches''. Double-end adjustabl ...

. 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. A drawback to tapered screw extractors is that their wedge action tends to expand the drilled, and thus weakened, screw. This wedging action can lock the screw even more tightly in place, making it difficult or impossible to extract. Square flute screw extractors Straight fluted extractors may come in a kit that also has associated drills,

drill bushing A drill bushing, also known as a jig bushing, is a tool used in metalworking jigs to guide cutting tools, most commonly drill bits. Other tools that are commonly used in a drill bushing include counterbores, countersinks, and reamers. They are desi ...

s, and special nuts, or be sold individually. The screw is drilled out with the appropriate drill and drill bushing. The extractor is then hammered into the hole with a brass hammer, because a steel hammer is more likely to cause the extractor to break. The appropriate special nut is then attached to the end of the extractor. The nuts can then be turned with a

wrench A wrench or spanner is a tool used to provide grip and mechanical advantage in applying torque to turn objects—usually rotary fasteners, such as nuts and bolts—or keep them from turning. In the UK, Ireland, Australia, and New Zealan ...

to remove the screw. Straight fluted extractors have less wedging effect than tapered screw extractors, so have less tendency to lock the screws into place. A further form is a parallel fluted extractor, with no taper at all and thus no wedging. These work well, but have the drawback of requiring the pilot hole to be drilled to a precise size. This size is often non-standard for most drill sets, requiring a dedicated drill bit to be supplied with the kit.

Bolts

A tool analogous to a screw extractor, but for removing a seized or rounded off nut from a bolt, is a nut extractor, which has tapered, spiral flutes like a screw extractor, but located internally in the tool, not externally. These flutes or grooves grip the rounded nut from the outside, rather than being driven into the hollowed out screw shaft and taking hold of it internally as a screw extractor would. Another tool for a stuck nut on a bolt, but not a screw, is a nut splitter.

References

{{Reflist Metalworking hand tools Screws