Fig. 2141.
The mallet is made in various forms to suit the nature of the work and the tools it is to be used upon. Thus the carpenter’s mallet is a rectangular block, such as shown in [Fig. 2141]. It is composed of wood, because the carpenter’s tools are held in wooden handles, and a metal hammer would split them in course of time. It is rectangular in shape so that it may be applied to tools held in a corner of the work, where a round mallet could not, if of sufficient diameter, give the necessary weight. For such carpenters’ or wood-workers’ tools as are for heavy duty, and the tools for which have ferrules at the head of their handles to prevent them from splitting, the mallet is made cylindrical or round, as it is termed, and has an iron band at each end to prevent the face from spreading or splitting.
The stonemason’s mallet is also of wood, and is disk-shaped, with the handle in the centre, the circumferential surface forming the face. The reason for this is that his tools are of steel and have no handles; hence if the blow continually fell on the same part or spot of the mallet face it would sink or indent holes in it, which is prevented by utilising the whole circumference of the mallet for the face.
An excellent mallet for the machinist’s use, for driving finished work without damaging it, is formed of raw hide secured in a metal eye that receives the handle. Or for the same purpose a lead hammer is used, being especially serviceable for setting work in machines.
What is known as pening, or paning, consists of hammering the skin of metal to stretch it on the side that is hammered. It may be employed either to bend or to straighten. Suppose, for example, we have a piece of metal that is bent to a half circle, and if we take a light hammer and hammer it on the concave side and all over its surface the piece will straighten out to an amount depending on the amount of pening. Or if he hammers the convex side the piece will bend to a smaller circle. The principle involved is, that if one side of a piece is elongated and the other remains of its original length, the only shape it can assume to accommodate or permit the elongation is that of a curve of which the convex side is the longest. It follows, therefore, that the hammer blows must in pening be sufficiently light to condense or stretch the metal on one side only of the metal, and not forcible enough to effect it all through.
In order to accomplish this stretching as rapidly as possible it is necessary to use a light hammer, with sufficient force to be expended in condensing the metal at its surface, and to so form the hammer that it shall expend its force upon the work with a dead blow, that is, with as little rebound as possible. These results are best accomplished with a ball pened hammer, such as shown in [Fig. 2108] and weighing about 1⁄2 lb. The blows should fall dead; that is, the hammer should fall, to a great extent, by its own weight, the number rather than the force of the blows being depended upon; hence, the hammer marks will not be deep. This is of especial importance when pening has to be performed upon finished work, because, if the marks sink deeply, proportionately more grinding or filing is required to efface them; and for this reason the force of the blows should be as near equal as possible. Another and a more important reason, however, is that the effect of the pening does not penetrate deeply; and if much of the pened surface is removed, the effects of the pening will be also removed. The work should not be rested upon metal, but upon wood.
Fig. 2142.