Glossary G.H.I


To treat with a bath of lead and zinc to prevent rusting  


Long term protection for structural fasteners is obtained by galvanizing to BS729 with a specified minimum thickness range of 0.4mm for the coating. Normal coating thicknesses range from 70 to 100mm; again the nut thread is overtapped by 0.4mm, to accommodate the coating.  

High temperature galvanizing, developed in the 1970's, results in a high quality surface finish with few of the imperfections of the traditional galvanizing process. Acid free cleaning processes make hydrogen de-embrittlement for BS4395 Pt2 fasteners unnecessary.  

Gimlet Point  

A taper-threaded point; applied to wood screws, Type A tapping screws, lag bolts, etc.  


To finish or polish a surface by means of an abrasive.  


The unthreaded portion of a bolt or screw.   

Half Dog Point  

The same as a dog point but half as long; used on short screws for the same purposes as the dog point, but in a shallower hole or slot.  

Hanger Bolt  

One endd is gimlet pointed and has a wood screw thread. The other end consists of a coarse machine screw thread. The center section is unthreaded.  


In a ferrous alloy, the property thaet determines the depth and distribution of hardness induced by quenching.  


A method of heat treating metals by heating to a temperature within, or above, the critical range, holding at that temperature for a given time, and then cooling rapidly, usually by quenching in oil or water.  


Resistance to plastic deformation by indentation, penetration, scratching or bending.  


The preformed, enlarged end of a bolt, screw, pin, or rivet, provided with a bearing surface which is usually either flat or conical.  

Header Point  

A chamfer point, usually of 45 degrees included angle, forming by a die at the time of heading and prior to threading.  

Head Marking  

Used to identify the material used in a fastener such as a bolt or cap screw. The marking is either raised or indented to specifications.  

Heat Treating  

An operation involving the heating and cooling of a metal to obtain certain desirable conditions or properties.  

Height of Thread  

The distance, measured perpendicular to the axis, between the major and minor cylinders or cones, respectively.  


Coil of wire used as an insert to accept a screw or bolt and adding holding power by forcing itself between the fastener and the walls of the recess when the fastener is driven in.  


A recessed hexagon socket in the head of a cap or set screw to add greater tightening and loosening power. Used with a Hex key wrench. (See Hexagon Head)  

Hexagon Head  

Flat top surface with hexagonal sides andn with a flat bearing surface. (Six Sides)  

Hook Bolt  

A "bent bolt" having the unthreaded end bent to form a hook, such as a round bend, square bend, right-angle bend, or acute-angle bend hook bolt.  

Hot Forming  

Working operation such as bending and drawing sheet and plate, forging, pressing, and heading, performed on metal heated to temperatures above room temperature.   


To remove small particles of iron or grit from the surface of stainless steel by pickling in an acid solution. 

Impact Test  

A test to determine the energy absorbed in fracturing a test bar at high velocity. The test may be in tension or in bending, or it may properly be a notch test if a notch is present, creating multiaxil stresses.  

Included Angle of Thread  

The angle between the flanks or the thread measured in an axial plane.  

Incomplete Thread  

On straight threads, that portion at the end having roots not fully formed by the lead or chamfer on threading tools:  


Steel formerly in a molten state, transferred to an ingot mold to solidify.  

Interference Fit  

A thread fit having limits of size so prescribed that an interference always results when mating parts are assembled.  

Internal Thread  

A thread on the internal surface of a hollow cylinder or cone.  

International Metric Thread System  

A thread form similar to the American standard, excepting the depth which is greater. There is a clearance between the root and mating crest fixed at a maximum of 1/16 the height of the fundamental triangle or 0.054 x pitch. A rounder root profile is recommended. The angle in the plane of the axis is 60 degrees and the crest has a flat like the American standard equal to 0.125 pitch.  


Primarily the name of a metallic element. In the steel industry, iron is the name of the product of a blast furnace containing 92 to 94 percent iron. Other names for blast furnace are pig iron and hot metal.