Material. Square-section carbon steel, spring steel such as large spring tines from cultivator or railway-line metal.
Additional tools. 10- and 20-mm top and bottom fullers, slot punch and drift.
The simplest of set hammers is shown as B in Fig. 142. The dimensions are for guidance only and can be varied to suit the metal available and the requirements of the smith.
Set-hammer faces are usually 25 to 30 mm square. For handles made from steel rod, the top or head of the set hammer is drawn-down as for previous tools. Fullering to accept the rod handles is carried out on the corners only. After forging, the tool is normalized and finished by grinding or filing with each edge slightly rounded (Fig. 142B). If you want to carry out hardening and tempering, bring the face end to red heat and quench in oil. Next, clean and polish the face and heat up the opposite end slowly in the fire while keeping the face uppermost. Heat will be conducted to the hardened end. When a dark-brown oxide colour is seen, quench it in water.
A side set is made in a similar manner with the face angled at approximately 60 degrees (Fig. 142C). Side sets are used for the rapid setting-in of shoulders for tenons.
Although adequate for most work, the set hammer with a handle made of metal rod is sometimes difficult to use with precision. A tool fitted with a wooden handle gives the smith a better grip and thus better work.
The eye is made by punching a slot hole and then opening this out to accommodate the wooden handle. A slot punch and a drift are required (Figs 144A and B). The slot punch is like a very small fuller, while the drift is a piece of round-section steel drawn to a taper as shown and finished to section by filing or grinding. These tools should be well-made and kept ready for use when other wooden-handled tools are to be made.
The slot punch is made from flat spring steel in the same manner as the fullers previously described. The working end can be 25 to 30 mm wide by 2 to 3 mm thick. If possible, the drift should also be from spring steel although axle-shaft steel will suffice. The drift is made by drawing-down to a tapered round-section point and then flattening. The 80-mm tapered length is given as a guide; it may be longer. If the section shown occurs about halfway along the taper, a proportionately larger section will occur farther along this taper, and it can be used for making larger eyes in other tools. Dimensions are not generally critical but should be somewhere near those indicated.
Forging is easier if a hand length of material is available. First mark off the centre of the workpiece on both sides and then mark the position of the hole, leaving enough material to form the head, about 35 to 40 mm from the end to the start of the hole. Centre-punch these positions. Take a good yellow heat in the position of the hole and carefully punch from both sides with the slot punch. The punch must be kept upright and cooled frequently. After the hole has been started, a little coal or coke dust sprinkled in to the hole will keep the punch from binding in the work.
When the slot hole is completed (Fig. 145), the hole is opened out with the drift (Fig. 146) but not to its full size. If you have trouble getting the drift to enter the work, an upsetting action (Fig. 150) will open the slot a little and make the job easier. At a good yellow heat, forge the head of the tool (Fig. 147), then trim all around with a hot set. This will make cleaning up the head easier.
Heat again to a yellow heat and fuller below the eye (Fig. 148) with a fuller of about 10 mm to a depth of 6 mm. This operation can be omitted, but the fullering makes it easier to site the position of the edge of the tool when in use. While at a bright red to yellow heat, drive in the eye drift to the correct depth from each side in turn to bring the eye to the required size and to make the eye taper toward the centre from each direction. While the drift is in position, slightly flatten the sides of the eye. Leave the maximum possible thickness of material around the eye to withstand hammer blows.
The formed tool is next separated from the bar by cutting with a hot set (Fig. 149). Cut evenly and squarely from all four sides. At this stage, if a good rough file or rasp is available, heat to a yellow heat and rasp off much of the unevenness from the cut face. Normalize it, and when it is cold either file or grind it to a flat face with slightly radiused edges.
On hot metal the tool will work well in this state, but it can be hardened and tempered. To do so, heat the face end to a dull red and quench it in oil. Clean and polish the face, heat up the drift or preferably another piece of steel tapered to fit the eye, place the heated drift or other piece in to the eye and watch for the oxide colours. As soon as dark brown to blue begins to appear, requench it in water.
Fit a smooth, comfortable wooden shaft about 300 mm long. The handle should be a firm fit. Most smiths, however, do not wedge these into place for anvil tools. Use your own judgement, but remember that if the handle is not wedged, the hammer must be watched closely or the head may fly off while you are using it.