Glossary of Fastener Terminology

N

Neck: Neck is used to define: (1) a specialized form of a portion of the body of fasteners near the head to perform a definite function, such as preventing rotation, etc.: and (2) a reduced diameter of a portion of the shank of a fastener which is required for design or manufacturing reasons. Various neck styles are fin neck, ribbed neck and square neck.

Nicked Threads: Nicks or indentations in threads can occur during the manufacturing process and during fastener transportation. In general, nicked thread problems tend to increase as the thread diameter increases and for fine pitches.
There are acceptance tests for nicked threads that involve measuring the maximum torque required to drive a GO gauge down the thread. Examples of acceptance tests are SAE J123 and the Ford Motor specification WA990 1993. Nicks and indentations in threads are sometimes referred to as gouges.

Nitriding: A surface hardening process used on ferrous metals by heating the metal in contact with ammonia gas or other nitrogenous material.

Nominal Diameter: The diameter equal to the external diameter of the threads.

Nominal Size: the nominal size is the designation used for the purpose of general identification.
Non-Ferrous Metal. Metals or alloys without an appreciable amount of iron. Examples are aluminum, brass, copper, etc.

Nonstandard Fastener: A nonstandard fastener is a fastener which differs in size, length, material, or finish from established and published standards.

Normalize: To remove internal stresses by heating a metal piece to its critical temperature and allowing it to cool very slowly.

Nut Dilation: Under load, the wedging action of the threads causes dilation of the nut resulting in an increase in the minor diameter of the nut, and reducing the effective shear areas of both the external and internal threads.

Nut Runner: A torque control fastener tightening tool that is usually powered by compressed air. The design of the tool is such that attempts are made to ensure that the applied torque is independent of joint stiffness.

Nut Thickness: Nut thickness is the overall distance from the top of the nut to the bearing surface, measured parallel to the axis of the nut.

Nut Width and Length: the nut width is the distance across opposite flats of hexagon, square or twelve-point nuts.

Nyloc Nut: A torque prevailing nut that uses a nylon patented insert to provide a locking feature. The nylon insert, it is claimed, helps to seal the bolt thread against seepage of water, oil, petrol, paraffin and other liquids. The nut is covered by UK patent 8028437 and European patent 81303450-1. Nyloc is a registered trade name of Forest Fasteners.

(Click on the letters below to browse the glossary terms)

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z