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A screw extractor is a tool for removing broken or seized screws. There are two types: one has a spiral flute structure, commonly called an easy out after the trademarked name EZ-Out;[ clarification needed ] the other has a straight flute structure. [1]
Screw extractors are intentionally made of hard, brittle steel, and, if too much torque is applied, can break off inside the screw that is being removed.
A spiral screw extractor is itself a coarse-pitched tapered screw thread. They are generally left-handed, for use on right-handed threads, though there are right-handed extractors for removing left-handed screws. The screw is first drilled 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. 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. [1] 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 extractors may come in a kit that also has associated drills, drill bushings, 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 to remove the screw. [1] 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.
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. [2]
Another tool for a stuck nut on a bolt, but not a screw, is a nut splitter. [3]
Taps and dies are tools used to create screw threads, which is called threading. Many are cutting tools; others are forming tools. A tap is used to cut or form the female portion of the mating pair. A die is used to cut or form the male portion of the mating pair. The process of cutting or forming threads using a tap is called tapping, whereas the process using a die is called threading.
A torque wrench is a tool used to apply a specific torque to a fastener such as a nut, bolt, or lag screw. It is usually in the form of a socket wrench with special internal mechanisms.
Drills are cutting tools used to remove material to create holes, almost always of circular cross-section. Drills come in many sizes and shapes and can create different kinds of holes in many different materials. In order to create holes drill bits are usually attached to a drill, which powers them to cut through the workpiece, typically by rotation. The drill will grasp the upper end of a bit called the shank in the chuck.
A bolted joint is one of the most common elements in construction and machine design. It consist of a male threaded fastener that captures and joins other parts, secured with a matching female screw thread. There are two main types of bolted joint designs: tension joints and shear joints.
A reamer is a type of rotary cutting tool used in metalworking. Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides. There are also non-precision reamers which are used for more basic enlargement of holes or for removing burrs. The process of enlarging the hole is called reaming. There are many different types of reamer and they may be designed for use as a hand tool or in a machine tool, such as a milling machine or drill press.
A socket wrench is a type of spanner, that uses a closed socket format, rather than a typical open wrench/spanner to turn a fastener, typically in the form of a nut or bolt.
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread. A screw thread is the essential feature of the screw as a simple machine and also as a threaded fastener.
A chuck is a specialized type of clamp used to hold an object with radial symmetry, especially a cylinder. In a drill, a mill and a transmission, a chuck holds the rotating tool; in a lathe, it holds the rotating workpiece.
A lug nut or wheel nut is a fastener, specifically a nut, used to secure a wheel on a vehicle. Typically, lug nuts are found on automobiles, trucks (lorries), and other large vehicles using rubber tires.
An impact wrench is a socket wrench power tool designed to deliver high torque output with minimal exertion by the user, by storing energy in a rotating mass, then delivering it suddenly to the output shaft. It was invented by Robert H. Pott of Evansville, Indiana.
An impact driver is a tool that delivers a strong, sudden rotational force and forward thrust. The force can be delivered either by striking with a hammer in the case of manual impact drivers, or mechanically in the case of powered impact drivers.
A screw is a mechanism that converts rotational motion to linear motion, and a torque to a linear force. It is one of the six classical simple machines. The most common form consists of a cylindrical shaft with helical grooves or ridges called threads around the outside. The screw passes through a hole in another object or medium, with threads on the inside of the hole that mesh with the screw's threads. When the shaft of the screw is rotated relative to the stationary threads, the screw moves along its axis relative to the medium surrounding it; for example rotating a wood screw forces it into wood. In screw mechanisms, either the screw shaft can rotate through a threaded hole in a stationary object, or a threaded collar such as a nut can rotate around a stationary screw shaft. Geometrically, a screw can be viewed as a narrow inclined plane wrapped around a cylinder.
A threaded insert, also known as a threaded bushing, is a fastener element that is inserted into an object to add a threaded hole. They may be used to repair a stripped threaded hole, provide a durable threaded hole in a soft material, place a thread on a material too thin to accept it, mold or cast threads into a work piece thereby eliminating a machining operation, or simplify changeover from unified to metric threads or vice versa.
An insert nut provides a threaded socket for a wooden workpiece, similar to a wall anchor. Insert nuts are inserted into a pre-drilled hole by one of two means: screw in and hammer in. In both cases, the external protrusions bite into the wood, preventing the nut from either turning or pulling out.
A screw and a bolt are similar types of fastener typically made of metal and characterized by a helical ridge, called a male thread. Screws and bolts are used to fasten materials by the engagement of the screw thread with a similar female thread in a matching part.
A nut is a type of fastener with a threaded hole. Nuts are almost always used in conjunction with a mating bolt to fasten multiple parts together. The two partners are kept together by a combination of their threads' friction, a slight stretching of the bolt, and compression of the parts to be held together.
A bolt is a form of threaded fastener with an external male thread requiring a matching pre-formed female thread such as a nut. Bolts are very closely related to screws.
Width across flats is the distance between two parallel surfaces on the head of a screw or bolt, or a nut, mostly for torque transmission by positive locking.
A centerlock wheel is a type of automobile wheel in which the wheel is fastened to the axle using a single, central nut, instead of the more common ring of 4 or 5 lug nuts or bolts.
