TIG from an Arc welder

[zardoz]

We often see Arc welders that are advertised as being able to be used as a TIG welder, with the adding on of a suitable piece of TIG kit. What exactly is this, how does it work, and does anyone know if my new fave beast below

The Oxford 300 oil cooled,

will it be suitable for this ? I realize there will be no high frequency starts etc, so what is the difference ? Can some more knowledgeable soul explain how it s done ?

 

[irondarren]

First thing is an oxford is AC, which mean you will only have AC TIG at 50hz. On inverters there is normally a switch or a setting change mode. Tig uses a lower basic voltage than Arc, at 140 amps an ARC welder might have 26volts but the same TIG setting will only be around 18volts. Hence you see many TIG/MMA units advertised as a 200 amp TIG, but they only run 180amps on the stick. My IFL unit is the same, but is advertised as 200 tig/180mma, its all to do with current draw from the mains. Having said all this you can get TIG conversion boxes for non TIG units some will introduce HF, check here
www.migtigarc.co.uk/TIG_Welder/tig_welder.html
at the bottom of the page there are a few, before you decide to part with any money to buy one speak to weldequip, he probaly knows more about them and my be able to get you a better deal

 

[Mikey D]

Not possible with the oxford you have , any inverter arc welder can be set up as a scratch start tig unit tho
cheers mike

 

[Drains]

To add to all the above...
Your AC set would do tig, if you had a rectifier to turn it to DC. Then it would scratch. You could put an HF box onto it and you'd have HF too.

You can't AC tig with that set without a constant HF overlay, as the HF is necessary to keep the arc going. But I think it is possible, though old skool. I've seen such things sold on the bay, made in the 60's or so:- oil cooled tranny, rectifier, HF unit. Need a small shed to store them in.

I'm not sure that the voltage differences make any odds, as any inverter will tig, regardless. Voltage is affected by arc conditions more than anything else (although open circuit voltage is as set by the machine). Most inverters do not have an alternative setting, though many do (better quality/newer ones), particularly if they have a lift tig facility.

 

[irondarren]

Most inverters do not have an alternative setting, though many do (better quality/newer ones), particularly if they have a lift tig facility.

Never owned a cheap one Si,but my 7yr old pico 140 has a switch for tig, My IFL has a flashy display that tells me what mode its in. I just assumed most inverters had them

 

[Drains]

Never owned a cheap one Si,but my 7yr old pico 140 has a switch for tig, My IFL has a flashy display that tells me what mode its in. I just assumed most inverters had them

Fair do's Daz. I have an old Lincoln (8 yrs or so), without a switch. Most of the cheaper ones these days are the same, but the likes of Lorch and obviously your Pico certainly do (pro sets). Electronics being as they are now, such fancy things are more common, nevertheless the lower end of the market is as we know, built down to a price.

My point really was about voltages - working voltage rather than open circuit, as once the arc has been struck the voltage will drop to whatever is required - a rutile rod will run different to a basic, different to a cellulosic, different to TIG. The open circuit voltage seems to be most important re striking and keeping the arc going, as with a cellulosic or lo hi on dc (75v+, commonly), even though the actual arc voltage may be much lower.