scratch or lift tig

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Hi,Reading about the three methods to start a tig weld (scratch, lift-tig/lift-arc an hf), I wonder which is the essential difference between 'scratch' and 'lift-tig'.As I did read, in lift-tig the electrode is in touch with the workpiece a very short time and only lightly (as when i put a pencil on a piece of paper to write).On lifting the electrode, the weling machine starts an arc.In het 'scratch' method you will not groove the workpiece I suppose, but only 'draw a light line' over the workpiece, in effect  to be seen as  a series of light touches....What is wrong with my reasoning here?(I also read, hf is dangerous for electronics in the neighbourhood, and to avoid this, lift-tig would be the preferred method of the three mentioned above.Thanks,oldwelderman
Reply:Scratch start is like stick welding - just move the electrode close enough for arc to start with gentle movement. HF should not be a problem as long as things are well grounded.Burt _____________________Miller Syncrowave 250Millermatic 211Miller 375 Plasma Cutter Hobart Handler 12010FtDrillBit.com
Reply:If your doing aluminum you'll need High freq.  lift arc is on the better machines.  Scratch start is like a stick welder with the cables switched to strait polarityIt seemed like a good idea at the time!
Reply:problem i have w/ lift, its hard to tack a frajile fitup.  tungsten pulls a lil on ur part.  scratch - not the case so much, easier for me to tackLast edited by 123weld; 7 Hours Ago at 08:29 PM.
Reply:best process depends on the welder. 60cycle transformer tig welders make the most HF noise. and must have the proper HF ground system. See an owners manual for suggestions. AC tig on these welders have the HF on all the time you are welding.In DC only when you start. A good square wave inverter only uses HF pulse to start the arc and restart the arc if the arc stumbles. In both AC and DC.You can lift arc start in AC and weld as long as the aluminum is very clean.Inverters only. Scratch and lift arc can pick up a little of the base metal and contaminate the tungsten and weld puddle. HF start avoids this.It all depends on what you are doing and how critical the weld is.
Reply:I have never compared lift vs scratch on the same machine.  I fine lift start to be softer, less violent than scratch.  Again, never compared same machined, since i never owned one that allowed the option.
Reply:lift-arc TIG usually has a dedicated mode on the machine specifically for it, so that when the arc is initiated it is a bit softer.  Sometimes there is an up-slope timer so the machine ramps up from it's minimum to whatever you have it set to, over a period of a second or so;  where as scratch-start usually develops the full amperage of the arc rather immediately, like when you use a pure stick welder to TIG.

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Reply:

Originally Posted by Oscar

lift-arc TIG usually has a dedicated mode on the machine specifically for it, so that when the arc is initiated it is a bit softer.  Sometimes there is an up-slope timer so the machine ramps up from it's minimum to whatever you have it set to, over a period of a second or so;  where as scratch-start usually develops the full amperage of the arc rather immediately, like when you use a pure stick welder to TIG.