Engineers' hammers are of two principal varieties, one class being named ball hammers, and the other class being termed pane hammers. A ball hammer is one which has a ball at one end, and at the other end a flat extremity named a face. A pane hammer is a wedge-ended hammer, the wedge-shaped part being the pane. Ball hammers are represented by Figs. 318 and 320, and are used for riveting and ordinary hammering; if employed to rivet, the ball of the hammer is first hammered into the centre of the rivet's end, in order to thicken the rivet in addition to merely spreading the extremity, and this thickening is effected by making the convex surface of the ball form a hollow in the rivet end, after which the riveting is completed with the flat face of the hammer instead of the ball. Wedge-ended hammers are denoted by Fig. 319, and these are useful for hammering in a gap or other opening which is not large enough to admit a broad face, also for bending and straightening, and for thinning extremities of bars and plates, also for riveting small rivets. That which is termed the flat face of a hammer is always convex to the extent of about an eighth of an inch at the centre, such a form being necessary for ordinary hammering, to prevent the edges of the hammer face damaging the work which is hammered.

Chisels

The chisels indicated by Figs. 321, 322, and 323, are chipping chisels, and are used with the hammer denoted by Fig. 320, which is termed a chipping hammer. Chisels of this class are employed to cut iron, steel, and gun-metal, and while a chisel is in use it is held in one hand so that the chisel is at an angle of about forty degrees with the surface which is to be chipped, and while thus held, the chisel is struck with repeated blows of a hammer until the surface is chipped. The chisel shown by Fig. 321 is a planing or smoothing chisel, and is used alone for chipping small surfaces which are to be planes; but for a large surface, the channeler or groover shown by Fig. 322 is first driven across the surface to make a number of grooves at a short distance from each other, and also at right angles to each other; after this, a planing chisel is driven across the surface to cut off the prominences which were left by the channeler. Channeling chisels are used also for cutting key-ways into wheel bosses, also for key-ways in bolts, rods, and axles. Fig. 823 indicates a pointed chisel which is used for making angular grooves, and for driving out hard pieces from a piece of work which is to be planed or lathe-turned, also for clearing inner corners of angular holes.