Links are also forged with bosses - either one, two, or three - as represented by Fig. 35. The slot of such a link is easily made while cold, and properly shaped by a machine for the purpose; consequently, it is not necessary to forge any slot in the link, except the maker is compelled to do so through want of slotting machinery.

When a link is to have one, two, or three bosses, the mode of procedure consists in making a link which is equal in width to the total width of the link, the bosses included. After such a link is reduced to the necessary width and thickness, and also curved, the bosses are produced by cutting off the superfluous iron or steel that surrounds the intended bosses.

The link is marked upon both sides of it while cold, and a chisel for cold metal is driven into the marks, and the superfluous metal is afterwards cut off while at a yellow heat, and thus the bosses are produced.

Another mode of making link-bosses consists in forging each boss separately, and afterwards welding them to the link. The boss-pieces are made by driving in fullers at each end of a thick piece, thus forming a boss between two stems that are welded to the link. A boss thus formed possesses a concentric arrangement of the layers and fibres, and, consequently, is very durable.

But the strongest sort of fink results from forging it of one piece, and producing the bosses by driving in a fuller at the extremities of each intended boss, and afterwards reducing the intermediate portions of the link to its proper width.

This mode requires a little arithmetic, to ascertain the precise length of metal necessary previous to drawing down or reducing by a fuller to form the bosses.

Previous to driving in a fuller, the fink is reduced to its total forged width and thickness : the length of metal required is then discovered by applying the author's rule in this form:

As the mean width of the link previous to forming the bosses is to the required mean width afterwards, so is the required mean length of the link to the mean length previous to forming the bosses.

The mean width of the link is ascertained by adding the width across the link at one of the bosses to the width across the link at that part which is without a boss. The sum of both dimensions is then divided by 2, and the quotient is the mean width required.

For forging purposes, it is sufficient to consider the link's mean or mid-curve to be an arc of a circle's circumference, and the length of this arc is the required mean length of the link when forged, supposing that no bosses were necessary. In such cases, the length of straight iron required would equal the length of the mean or mid-curve. But, bosses being intended, it is necessary to add the lengths of the semicircular parts of the bosses, and subtract the lengths of those parts of the link which will be occupied by the bases of the bosses.

The length of the link's mid-arc is ascertained by multiplying the number of its degrees by •017453, and multiplying the product by the length of the arc's radius.

The rule applies especially to small work, of iron. Steel links require the same length of metal as the mean length of the link after forging. Driving a fuller into the edge of a steel one produces a burr instead of lengthening the work, and a trimming-chisel is needed to cut off the burr to prevent it being hammered into the link.

Thick links are lengthened by fullers and ordinary hammering on an anvil, but thin ones require to be placed edge upwards in a groove, for the convenience of holding or maintaining the Work in an upright position during the hammering upon the edges.