Screw extractor
Encyclopedia
A screw extractor is a tool
used expressly for removing broken or seized screw
s. There are two types; one has a spiral flute structure, which is commonly known by the trademark
ed name Easy Out; the other has a straight flute structure. The tools are made of very hard, brittle
steel
; they can break off inside the screw if too much torque is applied, making the removal much more difficult.
The screw is first drill
ed out to the proper diameter for that extractor. The extractor is then inserted into this hole and turned counter-clockwise using a tap wrench
. As the extractor is turned the flutes on the tool dig into the screw, causing it to lock tightly and apply sufficient torque 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.
s, and special nuts
. 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 will 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
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.
Tool
A tool is a device that can be used to produce an item or achieve a task, but that is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose. Tools that are used in particular fields or activities may have different designations such...
used expressly for removing broken or seized screw
Screw
A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...
s. There are two types; one has a spiral flute structure, which is commonly known by the trademark
Trademark
A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...
ed name Easy Out; the other has a straight flute structure. The tools are made of very hard, brittle
Brittle
A material is brittle if, when subjected to stress, it breaks without significant deformation . Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a snapping sound. Brittle materials include most ceramics and glasses ...
steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
; they can break off inside the screw if too much torque is applied, making the removal much more difficult.
Spiral fluted extractor
A spiral screw extractor is itself a coarse-pitched tapered screw thread. They are left-handed, for use on right-handed threads.The screw is first drill
Drill
A drill or drill motor is a tool fitted with a cutting tool attachment or driving tool attachment, usually a drill bit or driver bit, used for drilling holes in various materials or fastening various materials together with the use of fasteners. The attachment is gripped by a chuck at one end of...
ed out to the proper diameter for that extractor. The extractor is then inserted into this hole and turned counter-clockwise using a tap wrench
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 adjustable wrenches, also known as bar wrenches, have one threaded handle...
. As the extractor is turned the flutes on the tool dig into the screw, causing it to lock tightly and apply sufficient torque 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.
Straight fluted extractor
Straight fluted extractors come in a kit that also has associated drills, drill bushingDrill 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...
s, and special nuts
Nut (hardware)
A nut is a type of hardware fastener with a threaded hole. Nuts are almost always used opposite a mating bolt to fasten a stack of parts together. The two partners are kept together by a combination of their threads' friction, a slight stretch of the bolt, and compression of the parts...
. 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 will 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
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....
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.