Glossary D.E.F


The removal of burrs by a secondary operation such as grinding.  

Deep Drawing  

Forming shapedd articles or shells by forcing sheet metal into a die.  


1. One of a pair of hardened metal blocks for forming, impressing, or cutting out a desired shape. 

2. (thread). A tool for cutting external threads. Opposite of tap.  

Die Casting  

A very accurate and smooth casting made by pouring a molten alloy usually under pressure into a metal mold or die.  

Die Chaser  

The separate cutting tools used in die heads, which actually cut the screw threads.  

Dog Point  

A cylindrical extension, or pilot, of diameter smaller than the minor diameter of the thread, commonly equal to about D/2 in length, with a conical section between it and the thread; usually used as a pilot in assembling or as the end of a set screw projecting into a fairly deep hole or slot.  

Double End Stud  

Threaded at both ends with standard Class 2A threads to take nut assembly.  

Dowel Pins  

Used as a holding pin with chamfered on one end. Drilled headed dowel pin (clevis pin) used - frequently removed fastener. 

Dowel Screw  

Both ends have Gimlet points, threaded similar to a Lag Bolt. The center section has a plain unthreaded shoulder. Used in joining two wooden members such as a leg to a table top.  


(v) To sink a hole with a drill, usually with a twist drill. (n) A pointed cuttiniig tool rotated under pressure.  

Drilled Head or Shank  

Used in AN Bolts and Machine Screws, etc.  

Drive Screw  

A piloted, multiple threaded screw with a large helix angle, used for permanent applications. It forms a mating thread as it is hammered or pressed into a prepared hole.  

Driver Head  

A head, on a bolt or screw, designed for driving the fastener by means of a tool other than a wrench, such as a screw driver. 

Drop Forging  

Forming metal, usually under impact, by compression within dies designed to produce the required shape.   


Structural fasteners are normally electroplated to BS1706: 1990 and a thickness of Fe/Zn 8 (previously Zn 3). This coating is sufficient to ensure protection from corrosion during on-site storage, before assembly. 

Higher grade fasteners to BS4395 Pt 2 must always be hydrogen de-embrittled  

Elevator Bolt  

A flat, plain, circular countersunk head bolt with a square neck to prevent rotation.  

Endurance Limit  

The maximum stress that a metal will withstand without failure during a specified large number of cycles of stress.  

Escutcheon Pin  

A piece generally used to join a plate or shield, to cover or protect softer or more delicate materials or actions.  

Expansion Bolt  

A combination of a "lag bolt" and an internally threaded split sleeve, designed for fastening to stone or concrete by inserting a sleeve into a hole in the concrete and expanding to a tight fit in the hole by turning the lag both with a wrench.  


A bolt having a head in the form of an open or closed anchor ring, or of a flattened and pierced section, with or without a collar or shoulder under the head.   


To machine a flat surface perpendicular to the axis at rotation on a lathe.  

Fastener Finder Assistant  

An online fastener solution finder designed to  identify  standard sheet metal fastener solution (if exists) based on product and application geometry and performance criteria  questions. 

Fatigue Strength  

The stress to which a metal can be subjected for a specified number of cyclic changes of stress.  

Feather Key  

A parallel key fastened in either the shaft or in the hub of a member sliding on it. When fastened in the shaft, it must be long enough to hold or drive the sliding member in any of its positions on the shaft. When in the sliding member the key need only be as long as the hub. 


A rounded filling of the internal angle between two surfaces.  

Fillister Head  

Rounded top surface, cylindrical sides, and a flat bearing surface.  


A thin projecting rib.  

Finished Hexagon Bolts  

A washer faced or chamfered bearing surface with a close body tolerance.  

Fin Neck Carriage Bolt  

A plain, circular, oval head bolt with two oppositely located fins to prevent rotation.  


The general term used to signify the range of tightness which may result from the application of a specific combination of allowances and tolerances in the design of mating parts. See  "Class of Thread"  

Flat Head  

Flat top surface and a conical bearing surface.  


When used as a stop or lock nut, the locking threads of the slotted top press inward against the bolt, lifting the nut upward and causing the remaining threads to bear against the lower surface of the bolt threads. (*TM)  

Following Flank  

The flank of a thread opposite to the leading flank.  


To shape metal while holt and plastic by a hammering or forcing process. Dies used in process.  

Form of Thread  

The profile of a thread in an axial plane for a length of one pitch.  

Free Machining  

The property that makes machining easy because of the forming of small chips, a characteristic imparted to steel by sulfur, etc.  

Full Annealing  

Annealing a ferrous alloy by austenitizing and then cooling slowly through the transformation range.  

Full-Size Body  

The body of a bolt or screw which has a diameter between the minimum and maximum limits of the major diameter of the thread.