J... Glossary of Fastener and Fixing Terminology
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GLOSSARY ALPHA LOCATOR
J BOLT
J shaped fastener threaded at one end used in roofing applications. A "bent bolt" having the unthreaded end reverse bent to approximately a semicircle Product
J NUTS
Spring sheet metal clips used to put a thread on sheet plate, used in conjunction with self tapping screws and machine screws Product
JACK NUTS
Also known as Molly nuts are a threaded inserts. The Jack Nut® (Molly) is a lightweight threaded fastener ideal for use in thin, soft or brittle materials. During setting, the legs of the Jack Nut® collapse to provide a firm anchor on the underside of the material. Jack Nut® is used extensively in vacuum and rotational moulding applications as its flexible grip range can accommodate fluctuation in the moulding process. Product
JAM NUTS
American term for a lock nuts, two lock nuts are jammed together The term is used for thin nuts used to lock against a second nut. When used in this way the thin nut should be adjacent to the joint surface and tightened against the thick nut. If placed on top of the thick nut the thin nut would sustain loads it was not designed to sustain.
JOINT CONTROL TIGHTENING
A fastener tightening method which allows a fastener to be tightened to yield. The angle of rotation of the fastener is measured relative to the applied torque, yield being assessed when the slope of the relationship changes to below a certain value. Sometimes called joint controlled tightening.
JOST EFFECT
The name given to the reduction in the frictional resistance that occurs in a direction different to that in which slip is occurring. This effect is used in many applications including the removal of corks from bottles. If the cork is first rotated the force needed to pull the cork from the bottle is significantly reduced. It is also the fundamental reason why threaded fasteners experience self-loosening. Frictional resistance is first overcome in the transverse direction by slip occurring on the joint resulting in the frictional resistance in the circumferential direction reducing to a small value. The torque acting on the fastener in the loosening direction (as a result of its preload) that when coupled with the Jost Effect results in self-loosening occurring.
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