setting up an old tig machine

[Jay reKx]

Hi
A few years ago I could tig steel to a fairly acceptable standard, but never got to experiment much with ally. Now several years have passed without me so much as picking up a tig torch and it seems I've forgotten just about everything I ever learned. Yesterday a friend asked me to weld some thin narrow aluminium angle for him and pulled out this dusty tig welder and handed me a bunch of filler rods:

Now I knew enough to switch it to AC, had the argon blowing at about 20psi, but apart from that, after a couple hours playing with the dials and a bit of trial and error, I still had to give it up as a massive fail. I've googled it, and watched several and various youtube videos, but a lot of them have super flashy space age machines with half a million dials named with confusing acronyms that this one doesn't have, or are dead basic with just a couple of switches, and quite frankly, not very helpful at all.

oh, and what does this 'crater' dial do?

theres no foot pedal. I dont think I ever used a pedal before, so I'm hoping this wont be a problem.

Can someone explain, or tell me roughly how these dials should be set so I have a fighting chance of sticking stuff toegther instead of reducing it to molten lumps? The stuff this chap wants doing needs butt welding; 3 quarter inch angle, probably 1.2-1.5 mm thick


any help much appreciated!
JKx

 

[hotrodder]

Up and down slope refer to the time taken for the current to ramp upto the welding current and down to the 'crater current'. Crater current is the point at which the arc extinguishes... it's to prevent/minimise pinholes/craters in the weld that happen if the arc is shut off before the weldpool freezes. Time is post flow which is how long the argon to continues flowing to protect the tungsten/hot weld

Reckon on around 40A/mm as a starting point (more for tacking). Very rough rule of thumb for postflow is 1 sec/10A... take that as a bare min for ally with an aircooled torch and at least 5 secs. Personal preferance plays a largish role in slope times, say not much slope up 2 + secs down. Crater current looks to be set as an amperage rather than a %... obviously less than welding current, i'd set it at less than 50% of your main juice. 20psi argon doesn't make sense, flow should be litres per minute (around 6 - 8) of cubic feet per hour. Too much can be as bad as not enough

Ally is quite different to steel, sub 1.5mm butts when 'cold' with TIG and a virgin with ally is gonna be tough. What flavour tungsten (colour code on the end if it's not been cut/rubbed off? Is the ally new/clean? Are you brushing it with a stainless wire brush to remove the oxide layer (more important if it's old/used/dirty)? If the filler rods are as old/dusty as the welder then scotchbrite 'em and give 'em a solvent wipe

 

[Jay reKx]

thanks hotrodder, thats very helpful. I have no idea what breed the tungsten electrode is/was, the colour code seems to have gone long ago. the argon isn't psi at all - my bad, I think its lb/f or maybe even cfm? I set it to 20 whatever it was anyway, but will adjust as advised. the ally was cleaned with a steel wire brush, but I'll scotchbrite it and the filler rods next time.

another Query though,
The 'time' dial on the bottom right of the pic didn't seem to make much difference to the gas flow. If I didn't spark up, the gas shut off as soon as I let go of the switch, If I did spark up for more than a couple of seconds, the gas flowed for 4 or 5 seconds after the switch was released, regardless of what the 'time' dial was set at.

many thanks for your help so far

JKx

 

[hotrodder]

It's crater time. My bad, glanced at the pic and assumed. It holds the crater current for whatever time you set it to by the looks of things, post flow sounds like it's probably fixed/automatic. Slope down and crater controls should effect how long the arc continues for after releasing the button i.e. releasing it activates the slope down timer and it winds down to the crater current, pauses there and then shuts off

The most common flavour of tungsten used for DCEN (steel/stainless etc) is thoriated (red). It can work on AC but is prone to splitting and melting weirdly... odd growths, multiple balls which in turn can cause the arc to wander around. If it's behaving itself or rounding off/balling up cleanly then you're pretty much golden

 

[Jay reKx]

ok, that all makes sense now, cheers! whilst I'm here, what are the best tungsten electrodes for AC? this one was quite messy and would blister with the wierd little ball growths after a minute or so
thanks for all your help!

JKx

 

[hotrodder]

Sounds like the ones you've got are thoriated. See this http://www.mig-welding.co.uk/wiki/TIG_Welding_FAQ#Electrodes_for_Aluminium , i'd suggest zirconiated (white tip)

 

[Jay reKx]

thanks again. rods ordered

JKx