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14. Forging a strap hinge

(to suit Job 13)

Material. Mild steel, 25 or 30 x 6 mm in a flat strap.

Additional tools. Round section punch with 8-mm flat end; 12-mm round drift; 18-mm bottom swage; hot set.

METHOD

Heat one end of the strap to a bright red heat and cut off about 6 mm from the end, cutting from one side only. This gives a neatly chamfered end. Reheat to a yellow heat and begin bending the strap close to the end over the rounded edge of the anvil face, with the long side of the chamfer downwards (Fig. 99). Turn the curve uppermost and continue forming (Fig. 100) until a neat eye is made that fits the drift. Reheat if necessary, replace the drift in the eye, place the job in the 18-mm bottom swage and flatten the back of the strap (Fig. 101). Mark out holes required; the first one should be about 30 mm from the eye and the others more or less equally spaced. Heat the strap and punch the holes. Correct any bending that results. Take a bright red heat on the flat end and trim from one side with a hot set (Fig. 98D). Heat the whole strap to a red heat, wire-brush it and allow it to cool.

Agricultural engineering in development

Figure 98

Agricultural engineering in development

Figure 99

Agricultural engineering in development

Figure 100

Agricultural engineering in development

Figure 101

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