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Practical answers on the consumable parts for a high-current air plasma torch: gouging, fine-cut and drag-cut sets, wear checks and fitting.
Gouging is a variation of cutting in which the arc is deliberately defocused, mainly by changing the nozzle orifice size, so the torch removes metal in a wide, shallow groove instead of cutting through. Gouging therefore uses its own nozzle and shield, designed for that job, rather than the parts you fit for cutting.Fit the set that matches the gouge you want, and check whether your machine has a gouging mode that adjusts the gas pressure before you start. Your manual's consumable chart shows which nozzle and shield belong in each mode.
Normal wear shows as a small round pit forming in the centre of the electrode tip, which slowly deepens with use. When the pit becomes too deep the arc can attach to the copper holder instead of the emitting insert and damage it, so replace the electrode before it reaches the point where it will no longer start or hold the arc.The pit depth at which to replace depends on the maker and the current, so use the figure in your manual rather than guessing. A pit that is ragged, off-centre or very black can also point to a problem with the gas, so check your air.
A new nozzle has a sharp, round orifice. Replace the nozzle if the orifice is nicked or notched, has gone oval or out of round, or has rounded-off edges. Slight enlargement of the hole is normal wear, but it shows up in the cut as more bevel, more dross on the underside and a wider kerf.Most makers advise changing the electrode and nozzle together, because a worn electrode quickly damages a new nozzle. Never refit a nozzle you have already judged to be worn, and keep it clear of slag.
Fine-cut sets are made for intricate, fine-featured shapes in thin sheet. They are designed to give squarer edges, tighter tolerances and a narrower kerf than standard parts, and they are normally used at the lower end of the machine's current range on mild and stainless steel.They are made for both hand and machine torches. On a machine table the result also depends on a rigid torch mount, good height control and a suitable cut speed. Maker guidance recommends a shield rather than a deflector for consistency and nozzle life, and expects small adjustments from one sheet to the next.