COMMON HAND-TOOLS 



263 



Machinists' hammers for metal work are made in three 

 forms as shown by Fig. 123. Fig. 123a represents a ball-peen 

 hammer, the small end of which is shaped like a ball; Fig. 

 123b a straight-peen; and Fig. 123c a cross-peen hammer. 



The sledge hammer, used many times every day by the 

 blacksmith, is a tool so large and heavy that two hands are 

 usually needed to wield 

 it. Sledge hammers are 

 also used for breaking 

 coal, those designed for 

 this purpose having a 

 particularly long head. 



(a) Ball- (6) Straight- (c) Cross- 



Peen Peen Peen 



Hammer Hammer Hammer 



FIG. 123. Machinists' Hammers. 



The heavy smooth-faced 



hammer, frequently used 



for driving wedges in splitting stone, is also referred to as a 



sledge hammer. The peen of a sledge hammer is usually 



made of steel. 



There is still another hammer called a lead or copper 

 hammer which is used for striking on finished parts that 

 would be dented by a steel hammer. The machinist never 

 uses a steel hammer on finished work. Other hammers 

 used for special purposes are the chipping and riveting 

 hammers. 



306. Kinds of Chisels. The simplest form of metal cut- 

 ting tool is the chisel, called a cold chisel. The mechani- 

 cal principle of the cutting edge of the chisel is that of the 

 wedge. Chisels for machine work differ from wood chisels 

 in several ways, the principle difference being that cold 

 chisels have no handles. There are many kinds of chisels 

 in common use in the metal trades, some- small and some 

 large, but all are generally made of % in. octagonal (8-sided) 



