Material. Flat vehicle-spring steel, 10 to 12 mm thick, about 35 mm wide and 100 mm long; round-section mild-steel rod 8 to 10 mm in diameter and 1 m long.
Additional tools. Top and bottom fullers of about 25 mm; flatten if desired for a finished surface; vice; file or grinder.
Hot and cold sets are important basic smithing tools and are subjected to much heavy work. They must be kept in good condition and replaced when badly worn. Although tools with wooden shafts are considered the best and the most comfortable to use, handles made from mild-steel rod are adequate and even preferred by some smiths. They are certainly the easiest to make and repair. Vehicle-spring steel is chosen because it is usually the most readily available and cheapest source of steel. The tool design is based on flat spring steel for the same reasons. Material from heavy vehicles or, if available, springs off railway rolling stock will provide metal of substantial size for larger tools. For this job, a piece of steel with dimensions similar to those in Fig. 109A will be needed.
Heat just over half the length to a yellow heat, place on the bottom fuller with about 35 to 40 mm overhanging the tool. Quickly position the top fuller, fuller to a depth of 6 to 8 mm (Fig. 110) then and lightly fuller the edges of the recesses formed to remove their sharpness (Fig. 111). True up the workpiece, reheat the short end to a yellow heat and forge it to a slight taper (Figs 112 and 113). This will form the head of the tool, which should be about 15 to 16 mm or a little more than the original thickness of the metal used.
If no grinder is available, the top of the tool should now be rasped or filed flat and then given a slight radius so that hammer blows are concentrated on the centre of the head when in use. If no grinding machine is at hand, the head of the tool can be finished later.
The forged head of the tool is now held in the tongs and the opposite end is heated to a good yellow heat and then forged to a long taper (Fig. 114). On heavy material, if a helper is available, a fuller can be used to speed up the drawing-down operation. A flatter may then be used to improve the surface finish. While hot, the thin end of the job should be cut back to leave a straight edge that can then be filed to the correct cutting angle (Figs 121B and C). Note that the cold set (Fig. 12IB) is left thicker than a set for cutting hot metal (Fig. 121C).
Next, heat the tool all over to a red heat and allow to cool in the air, lime, sand or ashes to relieve stresses (normalizing). When it has cooled, hold the job in a vice, find the centre of the handle rod, heat the rod at its centre point to a bright yellow heat and bend it so that it fits snugly into the fullered recesses and close to the sides (Fig. 115). Make sure of this by fitting the handle on to the job and adjusting it if necessary.
Reheat the end plus 80 mm or so beyond the bend to a bright yellow heat, place around the forged set (Fig. 115) and take a full turn tightly around the set (Fig. 116). With light hammer blows settle the rod closely to the sides of the set and bring the unbent lengths together (Fig. 117).
Some smiths like to put a twist in the rod handle close to the head of the set (Fig. 118). This is easily done by holding the rod tightly in the vice about 35 mm away from the set and, with tongs, turning the set to give the tight twist seen in Fig. 118. Cool the heated rod and set in water so that they can be handled.
Make sure that the ends of the rod are of equal length and that the straight lengths are lying close together.
Take a full-welding heat on these ends and hammer them together (Fig. 119). After welding, take a longer heat and open out a space next to the weld to form a handle end and an eye from which to hang up the tool in the workshop (Fig. 120). The finished tool is shown in Fig. 121A. The blade sections shown in Figs 121B and C indicate the thicker cold set and the thinner hot set as well as the appropriate angles for the cutting edges.
Hot sets are not usually hardened and tempered because any heat treatment is quickly spoilt when the set comes in contact with hot metal. Keep cooling the set after every two or three blows when in use and repair any damage to it immediately. Keep a fine-toothed file handy for correcting the cutting edge. The cold set must of course be hardened and tempered as for a cold chisel.
Either of the two heating methods may be used and quenching can take place in oil or water. If cracking occurs it will be either because of too rapid a quench, i.e. water instead of oil, or because the metal is worked at too low a temperature when forging. Spring steel must not be forged below red heat or above a yellow heat. At near-welding temperatures the metal breaks down rapidly because of oxidation. After hardening, tempering should usually be at a brown colour.
Tools fitted with rod handles are easy to repair and maintain because they can be readily heated and reforged in order to correct damage. This is of particular importance when the head of the tool has become damaged.