Glossary of Fastener Terminology

M

Machining: Machining is the process of forming the surface by cutting away material.

Major Diameter: This is the diameter of an imaginary cylinder parallel with the crests of the thread; in other words it is the distance from crest to crest for an external thread, or root to root for an internal thread.

Malleable: A commercial iron that is capable of being extended or shaped by beating with a hammer or by the pressure of rollers.

Maximum Material Condition: The maximum material condition of a feature of a fastener means the maximum amount of material permitted by the tolerance shown for that feature (abbreviated MMC).

Meanshift: The difference in tightening torque values produced by the same tightening tool on hard and soft joints. A hard joint typically gives a higher torque value than a soft joint. Generally speaking, the lower the meanshift of a tightening tool, the better it will be in achieving a specified torque value irrespective of the joint condition.

Mechanical Galvanizing: Mechanical galvanizing is a process in which powdered zinc is applied to a base metal using the principles of cold welding and barrel finishing techniques.

Mechanical Properties: Mechanical properties are those properties which involve a relationship between strain and stress. Hardness, proof load, yield strength and ultimate tensile strength are examples of mechanical properties. The final combination of the fastener’s mechanical properties gained during its manufacture. and post-treatment processing.

Metal to Metal Contact Flange Joint: A flanged joint in which a gasket is compressed by bolts - the gasket being located in a recess within the joint so that it is compressed by the bolt loads until metal to metal contact occurs. Unlike the FLOATING TYPE FLANGE JOINT, for metal to metal type joints there are no standardised gasket factor definitions, test procedures, nor generally acknowledged calculation procedures available.

Milled From Bar: Milled from bar fasteners are fasteners machined from bar stock on a lathe, screw machine, etc.

Minor Diameter: This is the diameter of an imaginary cylinder which just touches the roots of an external thread, or the crests of an internal thread.

Model Engineers Thread (M.E.): A thread based upon the Whitworth thread form that was established in 1912. A very fine thread (a 3/32 inch thread having 60 tpi for example).

Molybdenum Disulphide: A solid lubricant that acts as a high pressure resistant film. Can be used by itself as a dry lubricant as well as in with other solid lubricants and in oils and greases. Used in threads, such lubricants act as a separating film to prevent corrosion formation on the thread surface (even under adverse temperature and environmental conditions) ensuring the release of the threaded connection. Such films can also act as friction stabilisers.

(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