Glossary U.V.W


A "bent bolt" having threads at both ends of the rod and the rod bent at the middle to a semicircle or to two right angles, used for clamping.  

Undercut Head  

For short lengths of flat and oval head machine screws, the heads are undercut to 70 per cent of normal side height to afford greater length of thread on the screws.  

Under-size Body  

The reduced body of a bolt or screw, the diameter of which may range from below the pitch diameter to the minimum major diameter of the thread. Such a body diameter is found on some bolts or screws having rolled threads.  

Unified Thread Standards  

The basic American standards for fastening screw threads as agreed upon by standard bodies of Canada, the United Kingdom, and the United States. They are a complete and integrated system of threads for fastening purposes. Their outstanding characteristic is general interchangeability of threads achieved through the standardization of thread form, diameter-pitch combinations, and limits of size.  


1. A metal working operation similar to forging. 

2. The process of axial flow under axial compression of metal, as in forming heads on rivets by flattening the end of wire.   

Washer Face  

A circular boss turned or otherwise produced on the bearing surface of a bolt head or nut to relieve the corners.  

Weld Screw  

Projection welding applied to screws offer a means of providing attached threated members in sheet metal construction. Welding lugs on the head of the screw reduce the amount of current required for surface welding and provide fusion of metal at predetermined points.  

Welding Stud  

A "drive screw" having a flat fillister head, used as an anchorage for welding.  

Whitworth Thread  

A screw thread, also known as the British Standard Whitworth (B.S.W.), used principally in Great Britain.  

Wing Nut.  

One-piece, round threaded nuts with wing lugs for ease of manual assembly. Particularly suited to applications where frequent removal and replacement or adjustment are required  

Wing Screws  

Special screws with projection heads. Widely used in industry and home where a finger tightened screw is needed for frequent adjustments or for knock-down assembly applications. This piece is produced by pressing, forming, machining, welding or die casting. (Also available as 2 piece wing nut and studs, peened or welded together.  

Wood Screw  

A metal screw having a driver head, a gimlet point, and a sharp- crested, coarse pitch thread, for insertion in wood or resilient materials. It produces its own mating thread.  

Woodruff Key  

A semi-circular or half-round piece, resting in a circular groove cut in a shaft. Sometimes referred to as a half moon key. Largely used in machine building.  

Work Hardness  

Hardness developed in metal as a result of cold working. 

Wrench Head  

A head on a fastener designed for driving or holding by means of an externally applied wrench to the sides of the head.