The machinist uses hammers of three shapes: ball peen, cross peen, and straight peen, Fig. 45. The ball peen is the most common; it varies in weight from 4 ounces to 3 pounds. The cross peen and straight peen hammers vary from 4 ounces to 2 pounds and are used principally in riveting. Hammers are made from a good grade of tool steel, hardened, and drawn to a blue color at the eye and a dark straw on the face and peen. The eye is elliptical in shape, and the handle is fastened by driving wedges, either wood or iron, into the end of the handle, thus spreading it to fill the eye. The handle is of hard wood, preferably hickory, and of a length suited to the weight of the hammerhead. When the handle is properly inserted, the axis of the head stands at right angles to the axis of the handle.
Soft hammers are used for striking heavy blows where the steel hammer would bruise the metal or mar the surface. They are made of rawhide, copper, or Babbitt metal, and vary in weight from 6 ounces to 6 pounds. They are subject to rapid wear, but are indispensable in setting up and taking down machinery. Those of metal are so constructed that the soft metal can be recast in the handle.
Fig. 45. Hand Hammers.