Coupling nut

From Wikipedia, the free encyclopedia
Jump to: navigation, search
A coupling nut and its orthographic view

A coupling nut also known as extension nut is a threaded fastener for joining two male threads, most commonly threaded rod.[1][2] The outside of the fastener is usually a hex so a wrench can hold it. Variations include reducing coupling nuts, for joining two different size threads; sight hole coupling nuts, which have a sight hole for observing the amount of engagement; and coupling nuts with left-handed threads. These are used to make up long rod assemblies from shorter lengths of rods. The rods are threaded into the coupling nut for a certain distance. Coupling nut dimensions are described by the industrial fastener institute in standard IFI-128. It is given a plain finish. It is either cold drawn or hot rolled depending on the bar stock used. Coupling nuts threaded with two different thread sizes and profiles are called reducing coupling nuts.[1]


  1. ^ a b "Coupling Nuts". McMASTER-CARR. Retrieved 26 March 2013. 
  2. ^ "EXTENSION NUT / COUPLING NUT". Kisan Engineers Machine Tools. Retrieved 26 March 2013.