Glossary J.K.L


A "bent bolt" having the unthreaded end reverse bent to approximately a semicircle.  

Jackson Head  

A machine screw with a small oval head. (Trimmed oval head).  

Jam Nut  

(1.) A second nut forced or jammed against the main nut to prevent loosening. 

(2.) A thin nut.   


A small block or wedge inserted between shaft and hub to prevent circumferential movement.  


The recess cut for Woodruff keys produced by sinking a milling cutter of the right diameter and width into a shaft.  


A groove or slot cut to fit a key. A key fits into a key seat and slides into a keyway.  


A roughened surface produced by contact with a wheel which forces metal above the surface while making indentations below the surface.   

Lag Bolt  

A fastener having a square head, with a gimlet or cone point, and a thin, sharp, coarse-pitch thread, designed for insertion in wood or other resilient materials and producing its own mating thread.  

Lead Error  

A variation in the distance between the threads of a screw.  

Left-Hand Thread  

A thread is a left-hand thread, if, when viewed axially, it winds in a counter-clockwise and receding direction. All left-hand threads are designated LH.  

Length of Fastener  

The length of a flat bearing surface fastener is the distance, in a line parallel to the axis, from the bearing surface to the extreme point. The length of a countersunk head fastener is the distance, in a line parallel to the axis, from the largest diameter of the bearing surface to the extreme point. 

Lentil Head Screw  

Obsolete term for oval head screw.  

Liquid Honing  

A metal finishing process by forcing a stream of liquid, in which a very fine abrasive is suspended, against the surface to be finished.  

Lock Nut

A nut which, in addition to serving the purposes of an ordinary nut, has a special means for gripping a threaded member so that a relative rotation between the nut and the threaded companion member is prevented in use.