The Stud is also called a double-headed screw or a double-headed stud.  The fixed link function is used to connect the machinery. The double bolts are threaded at both ends, and the middle screw is thick and thin.  Generally used in mining machinery, bridge, automobile, motorcycle, boiler steel structures, hanging towers, long-span steel structures,s and large buildings. 

A bolt is a screw with a larger diameter or without a head, such as a double-headed bolt.  Generally, it is not called a "double-headed bolt" but a "double-headed stud".  The most common form of a double-ended stud is threaded at both ends with a bare rod in the middle. 

Most typical use: anchor bolts or similar places, thick connection, with ordinary bolts can not be achieved. 

Main Use 

1,Used in the main body of large equipment, needs to install accessories, such as a mirror, mechanical seal seat, reducer frame, etc.  At this time, the use of double-headed bolts, one end of the screw into the main body, the installation of the attachment after the other end with a nut, because the attachment is often removed, the thread will be worn or damaged, the use of double-headed bolts replacement will be very convenient. 

2. When the thickness of the connecting body is very large and the bolt length is very long, double-headed bolts will be used. 

3. It is used to connect thick plates and places that are inconvenient to use hex bolts, such as concrete roof truss, roof beam hanging monorail beam hanging parts, etc. 

Surface treatment 

Double-headed bolts generally need to be surface treated. There are many types of bolt surface treatment. Electroplating, blackening, oxidation, phosphating, and non-electrolytic zinc coating are commonly used.  However, electroplated fasteners occupy a large proportion of the practical use of fasteners.  Especially in the automobile, tractor, home appliances, instruments, aerospace, communications, and other industries and fields more widely used. 

However, for threaded fasteners, it is not only required to have a certain anti-corrosion ability in use but also must ensure the interchangeability of the threads, here also known as rotation.  In order to meet the requirements of "corrosion protection" and "interchangeability" in the use of threaded fasteners, it is very necessary to establish a special electroplating standard.