Material. Metal should be large enough to give 30 x 30-m square section without too much forging or cut from a hand length (tool steel or spring steel are best, but worn axle shaft from a tractor or car is also satisfactory).
Additional tools. Combined punch and eye drift; two pairs of tongs; fuller about 12 mm; set hammer.
Make or adapt a punch as in Fig. 124 to act as both punch and drift. On the workpiece, make a prominent mark (Fig. 125A). Bring steel to a bright red heat and punch as in Fig. 127. Care must be taken to ensure that the punch is exactly in the centre of the width of the metal and that the punch is at right angles to the piece. The mark should be off-centre on the long axis (as shown) to facilitate the placement of the punch. Punch well through from one side, removing and cooling the punch frequently. A little coal dust in the hole will help in removing the punch from the work. As soon as the position of the punch can be seen from the opposite side start punching from the second side, allowing the end of the punch to enter the tool hole of the anvil as it passes through the work. Punch must be hammered in from both sides until the hole is approximately the size shown in Fig. 124 (section).The hole must taper from both faces to produce a hole that is smaller in the centre than it is on the outside faces.
The punch may be loosened as in Fig. 128A. A few quick blows on both sides of the eye effectively ease the punch in the hole.
The peen end of the hammer head is drawn-down as in Fig. 129, using a fuller followed by a set hammer. The job is reversed, heated to a good red heat and the corners removed, as in Fig. 130. The face and the peen in turn may now be reheated to a bright red heat and rasped while hot to give a radiused peen and a flat face. The work is now allowed to cool slowly and further finishing can then be carried out with a file. If a grinding machine is available, use it to do this finishing work.
Because the quality of steels varies, some experimenting might be needed in the hardening and tempering of this workpiece. If spring steel has been used, heat up the piece slowly to a dull (very dull) red heat and quench in oil. Clean up both the face and the peen until they are bright and shiny. Take a rod or a punch that fits well in the eye. Heat this rod or punch to a yellow heat and place it in the eye of the hammer head. Heat will be transferred from the punch to the work and temper colours will eventually be seen on the polished ends. Usually the peen heats up a little more quickly than the face end.
When a dark brown (almost turning blue) is observed, quench the piece in water. If the colour is seen on one end first, cool only that end while allowing the other to continue heating. When both ends are at the correct temperature (colour), remove the punch from the eye and quench the whole job. All that remains is to fit a handle. A good wire-brushing will improve the appearance of the work.
Hammers of this type are easy to make and are suitable for all normal workshop uses. Lighter and heavier hammers can be made using smaller or larger sections of steel. If a ball-peen is required, the drawing-down operation (Fig. 129) is repeated on all sides to give a square but tapered section, corners are removed and the end rounded up with a file or on a grinding machine.
See Fig. 11 for the method of fixing the hammer shaft. The small metal wedge is made in a manner similar to that used for the ragged hinge pin in Fig. 97.