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post flow with scratch start tig

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  • post flow with scratch start tig

    I was playing with my scratch start setup and I got a few beads that almost look like a weld, I need lots more practice but I'm starting to see progress. I'm either too hot or moving too slow, I'm going to play with both next weekend.

    The only thing I haven't been able to figure out is how to break the arc without losing postflow. The best thing I've been able to figure out is to pull the torch away from the weld until the arc breaks (about 2 or 3 inches) and then go back for some gas coverage, but this obviously leaves my weld unprotected while it's molten. If I don't pull away far enough or go back too soon the arc restarts.

    How can I break the arc so I don't lose gas coverage?

  • #2
    Hi, pull the cable out of the welder? only yoking...
    Next step to make a foot control now that the first step is already working.


    • #3
      Hi again, just thinking about what you asked, I don't know how it's done in the real world but I reckon a relay on the primary windings of the welding transformer wired so that a switch would break the mains power. The contacts would have to be rated at 15 or so AMPS and 240volts or whatever power you're feeding the welder.
      It would be a bit like reaching over the bench and switching the mains switch off.
      Can anyone see a problem with this?


      • #4
        I'm new to scratch start tig as well and have been having the same issue. what i've been doing is quickly snapping the torch to the side with a whipping motion and bringing it right back about an inch higher from the workpiece for postflow. This motion takes about half a second, and this seems to break the arc much more easily than simply lifting the torch up, and adequate shielding is maintained. Only thing is if the torch is too close when you snap back, the arc will restart. Maybe someone more experienced with tig will have a better tip, though.
        As a related sidenote, I'm working on a solenoid controlled footswitch for my argon flow, So I won't have to turn it on/off on the torch all the time. Next will have to be a footpedal!
        Last edited by blaz72282; 10-15-2006, 12:21 PM.


        • #5
          Break the arc with a quick pullback, and return to position for postflow coverage. Done all the time, works well.

          You want to be a little careful a) to do it quickly to minimize the unshielded time, b) not make so much of a breeze that when you come back in the gas is blow away preventing postflow, and c) not to tap a new arc when you come back in. You pretty much learn what to do quickly, and then it is automatic.

          Remember that the ahield gas has a slight reducing effect, so if you get back in quickly, you won't totally lose the shield, the gas will displace oxygen rapidly when you return, and the metal will still be hot enough for the shield to reduce the small bit of oxygen that gets to the surface. Then, a light surface cleanup and Bob's your uncle.
          I may not be good looking, but I make up for it with my dazzling lack of personality