Chains. Chain-making being a distinct trade of itself, thoroughly reliable chains can only be made by men trained to the work, although some of the very small sizes of common chains are made by women, boys, and girls. Chains are of two generally distinct kinds—short-link or unstudded (frequently called close-link) chain, and stud-link or stayed chain. The former usually embraces the smaller sizes of chain up to inches, and the latter comprises ships' cables and other heavy chains. Short-link chain is made in the following manner: The end of the bar from which the link is to be made is heated, then cut to gauge, and while still hot is bent into U-form; the free ends are then heated to a white heat and flattened or scarphed by a hammer, and in this state they are brought together and welded so as to form the other end of the link. The flattening or scarphing of the two ends and the closing of them being all done in one heat, the scarphed ends are again heated to welding-point, and the link is placed in a suitable recess under a hollow-faced tool, worked mechanically, which strikes the roughened weld and ultimately finishes it off as smooth as the other end of the link. The result is the finished link, and when the first has been completed, another piece of iron is bent in the same way and threaded or rove through it, and another link formed and finished in the same manner as the first. In this way each successive link is added until the required length of chain is made.
The foregoing illustrates the way in which chains generally are made, but as a rule, links of chains of 1-inch diameter and over are welded at the side instead of at the end, and a stud or stay-pin is welded across from side to side of the link. The larger sizes of chains and chain-cables are made by men, and the expert workman when employed making first-class chains of all descriptions gets an extra price for his skill and labour. Common (not to say inferior) chains, however, are too often welcomed by bargain-loving users if they can at all be made to pass the statutory tests. Chains which stand certain of the standard tests may be found totally unequal to meet certain others, and superior and inferior parts are often purposely mingled in one chain by dishonest makers to cheapen production and defeat the system of testing. The iron used for very superior chains is selected not only for its tensile strength and welding properties, but for its ductility, as high tensile strength is not infrequently possessed by a hard brittle iron, liable to snap upon the application of a sudden jerk, and therefore totally unsuited for chains. The system of testing cables followed by Lloyd's Register Society well exemplifies what should be adopted in the case of all chains. Every 15-fathom length is subject to a fair standard strain, sufficient to detect bad workmanship, by pulling asunder or opening any defective welds, yet not so severe as to injure the nature of the material by crystallising it—a result invariably produced by overstraining. This standard test, however, not being the extreme limit of strain which the chain ought to bear in actual use at sea, a few links are required to be cut out at random from any part of each 15-fathom length, and submitted to a so-called breaking strain of 50 per cent. in excess of the standard test. If these trial pieces are found to withstand this extra strain satisfactorily, they are then assumed to represent a fair average of the strength of that particular length to which they belong. This operation being gone through with satisfactory results in each length of cable, the whole is then passed, and certified accordingly. Any unsatisfactory lengths are condemned, marked, and sent back to the manufacturer.
In his treatise on Chain Cables and Chains, Mr T. W. Trail, surveyor-in-chief to the Board of
Trade, says: 'Since the Act of 1871, which came into operation in the early part of 1873, until the latter part of 1883, a period of about eleven years, nearly 165,000 tons of chain have been certified to, in accordance with the act of parliament, as having duly withstood the statutory tests, representing about 3,199,000 fathoms of chain, and for which it is computed that from about two and a quarter million to about two and a half million pounds sterling have been paid.'