ending arc

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Well i finally had time to run out to a friends shop and pick up some scrap stainless and mild steel to screw around with.  Since this is my first time welding, i had no clue what the hell i was doing, but i did have fun!my question is, how do i end my arc with a scratch start tig?  i have a two piece torch and havnt had time to pick up a pedal yet, but is that was is needed to end it and not take the weld out of the gas flow?  i will post up picks later when i get some more time to mess around with it, right now its off to a bachelor party. thanks for the help!also some tips on preping the metal would be awesome to.  i hit it with a little air grinder and then with an ss brush.  Do you have to use acetone for a clean weld or does it just speed along the cleaning process?
Reply:Last question first, the purpose of acetone is to remove oils which can porosity and hydrogen embrittlement (depending on the metal).  If you sand or grind the metal first, this may tend to spread oil/grease around and contaminate your sander/grinding disk, so it is best to degrease the part as best you can first, then grind/sand to remove rust or scale, then a final wipe with acetone for good measure.To the stop the TIG arc, the best way depends on your welding power supply, do you have a remote current control connection or not?If you have a remote current control connector on you power supply, get a foot or finger control to activate the weld power contactor and control current level.  At the end of the weld, pause and fill the crater as you downslope the current to extinguish the arc, then hold in positon and shield the end of the weld as it cools.If you have a remote connection, but you don't have a foot pedal or torch finger control, you can simply mount a tiny switch to your torch and wire it between pins A and B on the remote connector to activate and deactivate the weld power contactor.  When the weld is complete, fill the crater, hold in position to keep gas on the weld and switch the arc off.  This is what I have on my scratch start system, an on/off switch on the torch that I use when not using the foot pedal.If you do not have a remote contactor connector, and your torch is simply LIVE as soon as you turn on the main power, then all you can do is quickly pull the torch away at the end to break the arc.  That is, after you have properly paused and added wire to fill any crater.  I've never tried this, but maybe there is an advantage of breaking the arc by rapidly reversing direction and speeding up travel to narrow the melt and avoid a large final puddle that may be prone to crater cracking,  then pull away to break the arc?edit:  Sorry, just re-read your post and see that apparently you have the capability for a remote current control.Last edited by pulser; 07-23-2008 at 06:45 PM.
Reply:I have welded with and with out a remote.  The remote I thought was a luxury, but its almost a necessity.  For years all I had was an engine drive and a hi freq box for AC tig.  I used them and made good welds.  THEN I bought an inverter with foot pedal, gas valve..... What nice stuff!My welds always were good, but the ones with the remote control (foot pedal) were indeed better.  Once the arc is started, the heat can be reduced as I get to the end of the weld.NOW I have an invertec V155-S with no remote or hook up for one.  I have used it on jobs doing Tig work.  It is OK, except the trouble you are having.  I pull the torch away from the work quickly then once the arc is out, put the torch back over the weld for the gas coverage.  It is not as easy, but can be done.  I am thinking about taking the machine apart and installing a Double pole switch and a remote.Fill the end of the weld well and yank the torch away to put the arc out.  I am always surprised how long an arc it will continue to make.  Sometimes you can see where the arc went as I pulled the torch away.Bottom line, if you can get a remote.No, I don't use acetone, but I do use a degreaser if needed.  Grinding dry metal so there is no rust of mill scale is good enough for me.  If you grind it, the brush is not needed.  Clean freshly ground steel welds great for me.DavidLast edited by David R; 07-23-2008 at 07:04 PM.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:^^^ What he said.  Flick the arc out of there quickly, and once its extinguished, move the torch back for some post-flow.  If you're welding flat or horizontal, you've usually got a small window of opportunity since the argon, being denser than air, will hang around for a few seconds.  Welding overhead, well, not much else you can do.
Reply:thanks guys, well the machine is a invertec v300 pro so it has remote hook up, i guess i will look into a on off switch until i find a used foot pedal. And yes, it is amazing how long you can get yoiur arc, like 3 to 4 inches when i was welding at like 70 amps.
Reply:also could i just use mineral spirits since i already have it? it degreases and drys with no residue so i dont see why not, but just want to check
Reply:Test it out first.  I won't use mineral spirits because its petroleum based and can in fact leave a very fine residue.  If you try it and it works fine, go ahead, but I only use acetone or alcohol.
Reply:V300.. You got a good machine there.  Get the foot pedal and find out its more than a luxury.Look at my sig, I have a few of those V's.David Real world weldin.  When I grow up I want to be a tig weldor.