Upon the principles underlying the shapes, sizes, and uses of hammers, much will be found under the heading of Carpentry. A few representative forms of hammer head are shown in Figs. 18,19: a to d are used by engineers and mechanics, e to k by boiler-makers, while l is a sledge hammer. All but l are hand-hammers. They differ mainly in the form of the pane, the head remaining pretty much the same; a is a cross pane, b a straight pane, c a ball pane, and so on. Hand-hammers mostly range between 1 and 4 lb. in weight; chipping hammers, 1/2-1 1/2 lb.; riveting hammers, 1/2-2 lb.; sledge hammers not exceeding 8 lb. in weight are "uphanded," i.e. only raised to a little above the shoulder, while the heavier ones (8-1G lb.) are "swung" in a complete circle. The machinists' hammer is made heavier at the face than at the pane end, so that the hammer will naturally assume a position in the hand with the face downwards, thus relieving the workman from the necessity of specially forcing it into that position.

In using a hammer it is essential to study the difference between a sharp blow with a light hammer and a blow blow with a heavy one: the former penetrates farthest and gives least lateral pressure; while the latter penetrates less and spreads more sideways.

Hammers 20Hammers 21