Glossary M.N.O

MS Specifications  

(Military Standard)  


Relative ease or difficulty in forming.  


A magnetic method of determining surface and subsurface defects in metals.  

Major Diameter  

On a straight thread, the diameter of the coaxial cylinder which would pass through the crests of an external thread or the roots of an internal thread.  

Master Gage  

A thread-plug gage which represents the physical dimensions of the nominal or basic size of the part. It clearly establishes the minimum size of the threaded hole and the maximum size of the screw at the point at which interference between mating parts begin.  

Maximum Material Limit  

The maximum limit of size of an external dimension or the minimum limit of size of an internal dimension.  

Mechanical Properties  

Those properties of a material that reveal the elastic and inelastic reaction when force is applied, or that involve the relationship between stress and strain; for example, the modulus of elasticity, tensile strength and fatigue limit.  


One millionth of an inch. Used in measuring imperfections of surface finishes.  

Milling Process  

A machining process whereby a surface is generated with a rotating toothed cutter. Each tooth takes an individual chip.  

Minor Diameter  

On a straight thread, the minor diameter is the diameter of the coaxial cylinder which would pass through the roots of an external thread.  


A corrosion resisting metal consisting essentially of two-thirds nickel and one-third copper.   

NAS Drawings and Specifications  

Dimensional and material standards for aircraft fasteners developed by the National Aerospace Standards Committee. All drawings and specifications are prefixed by "NAS" .  

Nail Point  

A sharp pyramidal point of approximately 30 degrees or 45 degrees included angle.  

Naval Brass  

A corrosion resistant metal containing 60 per cent copper, 39 1/4 per cent zinc and 3/4 per cent tin.  


A portion reduced in diameter between the ends of a shaft.  


A silver-white metal usually used as an alloy in steel, bronze, brass and cast iron. It tends to increase corrosion resistance.  


A short piece of threaded pipe used to connect two fittings.  


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

Non-Ferrous Metal  

Metals or alloys without an appreciable amount of iron. Examples are aluminum, brass, copper, etc.  


Steels with sufficient quantities of manganese or nickel to render the steel non-magentic. 18-8 (300 series chrome-nickel steel) is non-magnetic when annealed. Type 316 is non-magnetic in all conditions. (See pg. 156 of the Data Book).  


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


A metal block (solid nut) or sleeve having an internal thread made to assemble with the external thread on a bolt, screw, or other threaded part. It may be a fastening means, an adjusting means, a means for transmitting motion, or a means for transmitting power with large mechanical advantage and nonreversible motion.  

Nylon Fasteners  

Fasteners made of a material that has a low dielectric constant and relatively high tensile strength, enabling it to resist high voltage at commercial frequencies. It can also operate at continuous temperatures as high as 250 degrees F. Any temperatures above has an effect to oxidize material. Electric and electronic equipment manufacturers are finding many corrosion-resistant applicables for this type of fastener.   

One-Way Head Screw  

A round head screw which is slotted but has side clearances at diagonally opposite sides of the slot so that the screw can be driven only in the direction of assembly, designed for preventing tampering.  

Open Washer  

A washer with one side open so as to be removed or put under a nut without removing the nut.  

Oval Binding Head Screw  

Obsolete term for a truss head screw.  

Oval Head  

Rounded top surface and a conical bearing surface with an included angle usually of 82 degrees.  

Oval Point  

A rounded end which is used, particularly for set and adjusting screws, to apply pressure without cutting action.  

Oven Head Screw  

Obsolete term for truss head screw.