TIG Welder - P&H

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TIG Welder - P&H
Control panel.jpg
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Name P&H Tig Welder
Owner i3 Detroit
Make Model P&H Tig Welder
Part Number DAR-300HFSG
Date Acquired
Storage Location Welding Area, against the wall.
Authorization Required
Other References * Welder consumables are on this list: Welding Shop Consumables




  • Turn on the Argon Gas bottle at the wall rack. Remember that the seal system for inert gas only completely seals the stem at full closed and full open. Turn the knob in the desired direction until it stops. When the TIG machine is turned on, you can adjust the argon flow (watch the red ball in the vertical glass tube).
  • Check the power switch on the junction box on the wall. Is it turned on?

Quirks of the I3 P&H TIG machine.

  • Sometimes the foot pedal sticks just enough to turn on the solenoid. This is very bad, particularly if you are using an old style welders shield. Its too easy to flash your eyes in error. Best action, is to ensure foot pedal is at top of stroke before you turn on the machine.
  • Argon use. The machine flows argon gas whenever the machine is turned on. Argon gas is expensive. This means turn off the machine when you have finished your weld, and don’t turn it on again until just before you are ready to run your next bead.
  • High Frequency -- The switch has 3 settings, Start, Off, and Continuous. HF provides a secondary electrical wave that jumps gaps much more easily, but doesn't really make much heat. It's used to help start the arc for DC welding (Start) and to help maintain the arc during AC welding (Continuous). It can disrupt radio communications, so if you plan to listen to music while welding Aluminium, an MP3 player is going to work better than a radio.
  • Duty Cycle -- The machine has a duty cycle of 60$ at full capacity, meaning that it should be given a 4 minute break after 6 minutes of solid welding. This only becomes a concern when welding really thick materials, as the duty cycle goes up to 100% pretty fast as the amperage is reduced. If you are welding with the machine in the "High" range on DC or the upper "Middle" Range on AC, make sure you understand what that means for the duty cycle. If you are on Low range or Middle/DC, no worries.

Machine settings: What material are you welding?

  • Steel? If you are using steel, set the Polarity Selector Switch (large three position switch on the right hand lower area) to the full clockwise position, Direct Current Straight Polarity (DC Electrode Negative). You should be using the red tungstens (2% Thoriated) for DC TIG welding. Set High Frequency to Start.
  • Aluminum? If you are using aluminum, set the Polarity Selector Switch to the full counterclockwise position, Alternating Current (AC). You should be using the green tungstens (pure tungsten) for AC TIG welding. Set High Frequency to Continuous.

Maintenance Info

  • Spark Gap
    • The welding arc should start immediately while High Frequency is on Start or Continuous. If it doesn't, verify that the front panel controls are set properly. If it still doesn't, the spark gap may need maintenance as described in Figure 3-8 of the online manual. The manual recommends a 3 month or 250 hour interval for spark gap maintenance.
      • Unplug the welder.
      • Remove the right-hand side panel.
      • Locate the high-voltage capacitor, which is a few inches from the spark gap, and connected to it with a short wire. Manually discharge this capacitor through a conductor that is not a living organism.
      • Leave the center spark gap electrode bolted tightly in place.
      • Loosen the bolt that holds down one of the end electrodes. Insert an 0.006 feeler gauge into the gap, push the end electrode hard enough to squeeze the feeler gauge, and tighten the bolt. Verify that you feel a slight resistance when you slide the feeler gauge through the gap.
      • Repeat the previous step for the other end electrode.
      • If you need to clean or resurface the electrodes, which is unlikely, take care to maintain the parallel alignment of the gap.
      • Put back the side panel, and plug the welder back in.
    • The spark gap was last adjusted on 2012-10-09 by Dave Scholl and Jody Raiford.




Control panel.jpg

Other machine settings?

  • Set the large Output Control knob to desired setting. The foot pedal will control the actually amperage output to the maximum set on the dial. If you need less heat, back off on the foot pedal. If you need more heat, press the foot pedal further down.
  • Flipper switches, set: Remote Control , Soft Start Operative / Inop (per users discretion), Inert Gas Arc Welding, High Frequency Starting Continuous (per users discretion).
  • There are two small black dials on the right hand side of the machine, These are for the high frequency start circuit. Normally both of these knobs are set such that the white indicator line on the knob is vertical.

Getting ready to weld.

  • Prepare all of your materials. Ensure you have clean metal, including stainless steel wire brush on all aluminum to remove the surface coat of aluminum oxide.
  • As a general rule, set tungsten extension “stick out” distance equal to the diameter of the electrode. You may have to extend it further to reach some welds as required, but note this makes it harder to ensure inert gas coverage, etc.
  • As a rule of thumb, while TIG welding, arc length (the distance between the end of the electrode and the work piece) is: One electrode diameter for A/C TIG welding, and usually considerably less for D/C TIG welding. Be careful to not allow the hot electrode to contact the weld puddle, or the filler rod. If you do touch, you will see a flash of light, and molten material will wick up and contaminate the tungsten electrode. When that happens, you should stop, regrind the electrode.
  • If you want to get better, Practice, Practice, Practice!!