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156 
APPLIED POWER INDUSTRIES INC. (U.K.) LTD.
Page 73
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717 Tudor Estate, Abbey Road, Park Royal, London, N.W.10.
ONLY one spot welder is included in the range of equipment offered by this concern. This is the Blackhawk Spot-Right, which is a welder for one-sided approach. The gun is used with a special power pack on which one terminal is connected by a clamp to the work, whilst the other is connected to the gun.
An electric arc is struck as the electrode of the gun contacts the surface of the metal and which burns a hole through both metal sections to be joined, fusing them together at the edges of the hole. After fusion has taken place, the molten metal deposited by the electrode and its powdered-iron coating fills in the hole, leaving a raised surface which can be sanded flat without further filling. When the right amount of weld metal has been deposited the arc is automatically extinguished. There is a nozzle shield around the electrode which serves to concentrate the heat in the one spot and eliminate distortion of thin sheets being worked on.
Operation of the Spot-Right is quite simple and there are only three settings on the power pack for output. Adjustment for penetration and build up is given by a Vernier-type control on the gun itself ; the timing mechanism does not rely on an electronic relay, but is operated by a mechanical lock which limits the amount of electrode that can be melted. It is possible to join together panels varying in thickness from 16 to 22 s.w.g. and to weld these thicknesses of sheet to thicker metal.