Common welding related questions we hear. Part 15
Pre-sales calls about TIG welders often come around to the discussion of arc starting styles eventually. Many times I have had customers ask me if we had scratch start TIG mode on our AC/DC welders. I’ll reply,” No, but we have lift start”. They’ll then ask, “It’s the same thing isn’t it?” “No, it isn’t” I reply.
Then I’ll begin to discuss the differences in them. Scratch start is a raw, crude way of starting an arc, used almost exclusively in DC mode. By comparison to lift start, it may seem to be quite barbaric. To start the arc, the torch is flicked quickly across the surface of the metal, with a more compact, yet similar motion to striking a match. This causes loss and contamination of the tungsten as the arc initiation often wants to make the tungsten stick or weld itself to the metal if not done flawlessly.
This can be a serious problem on X ray quality welds. However, many a nuclear power plant has been built with this method of welding. It may even fail to create a sustainable arc and is often difficult to master by the TIG “newbie”. It’ll definitely require a lot more grinding and reshaping of the tungsten than any other method. These are often coupled with “TIG” Rigs where an inexpensive transformer DC stick welder, or even a DC power source such as a generator welder to weld. These TIG rigs include a power cable, a powerblock, a gas-valve tig torch and a regulator. The gas valve TIG torch is used in lieu of a gas solenoid which is often missing on simple DC output machines.
Gas flow is turned on and off manually. Power output is constant so that a TIG torch set down on the work surface when not in use should have an insulating buffer between the tungsten and the work piece…many times a rubber hose slid over the nozzle will suffice.