forged stem of one piece (the male) contains a series of parallel
serrations giving an appearance of concentric rings. The other socket
piece (the female) has holes at each end. in joining the two pieces to
form a link, the pierced socket section is heated, then the stems of the
other section are inserted into the holes. The socket section is then
forged with a drop hammer, forcing its material around the indentations
in the other piece's stems, while both pieces are held in die blocks (see
Each chain link is made to commercial link standard
dimensions, which are 6 wire diameters long by 3.6 wire diameters wide.
Flash Butt-Welded Chain. Each link of this chain is formed by bending a
heated rod into an open chain link shape and flash welding the two butt
ends. While the link is still hot, a stud is inset-ted and the link is pressed
on both sides to secure the stud. After cooling, one or both ends of the
stud may be welded to the link (see Figure B-4).
1.3.2 CHAIN GRADES. The properties of the steel used in the manufacture of chain
for the Navy follow specifications that are similar to the rules followed in the
manufacture of commercial chain. For commonly available chain, there are three
different material qualities designated: Grades 1, 2, and 3, respectively. Grade 3
(which is used as FM 3 chain) has the highest strength of the three and is the grade
currently being procured by the Navy for fleet mooring use and is singularly suited
for application of a cathodic protection system. Figure B-5 depicts a comparison of
the breaking strengths of these different materials.