Automatic electric wire welder No. 64, with board of 19 specimens and 3 gauges, by The Electric Welding Co., Maidstone, Kent, 1904

This is a small machine, made by the Electric Welding Co Ltd, for welding wire by the process introduced by Elihu Thomson in 1886, in which the heat is produced by the passage of a heavy electric current through the proposed joint while the parts are pressed together.

The pieces to be welded are prepared by having their ends made slightly convex and are then firmly held in clamps, one of which is urged towards the other by an adjustable spring having a controlling handle and locking arrangement. The clamps are insulated and form the terminals of the secondary coil of a step-down transformer, the low resistance of which causes the heating to be confined almost entirely to the junction, at first through the imperfect contact and afterwards through the higher resistance of the hot metal; the convexity of the ends, moreover, causes the welding to commence at the interior, so that any scale is expelled and a good joint is obtained throughout.

The controlling handle, which regulates the approach of the terminal clamps, has an adjustable sector connected with an arm operating a switch in the primary circuit of the transformer, and is so arranged that when the clamps have approached each other sufficently, through the up setting of the metal, to ensure a good joint, the circuit is automatically broken.