Tungsten Size

[HasBean]

As it's my evening for posting, just one more

Had my first go at tig at the weekend using a filler rod (1.6) Had to use a disposable cylinder so guessing 6lpm at full welly. 3/16 plate 80A No 7 shroud, 2.4 tungsten.

Weld was 'interesting' (read c**p)

However I understand current/gas flow but not the relation for tungsten size and shroud/cup size
Guessing small tungstens can use smaller cups for recessed areas (?) but can you use, say, a 2.4 tungsten with a No 6/7/8 cup on lower amps?
Basically, as I said, can't understand the relation. Had a look at the Miller site which is very good but maybe it's just me (more than likely )

Can anyone enlighten me or point me in the direction of a good site/book which is sympathetic to the hard of thinking

Paul

 

[shenion]

I suggest you use the Miller TIG calculator.

 

[HasBean]

Hi Shenion, thanks for the reply.

I've seen the calculator before but it's the maths behind it I don't understand.

i.e. is the cup related to tungsten size or gas flow? Is the current related to material thickness or tungsten size? I understand that a thicker material requires more current therefore a larger tungsten but can you not use a larger tungsten for thinner material, maybe just increasing the amps just a bit to compensate for the larger rod if thats the case?

I really don't know so appologies for being a bit thick, it's just that when I want to know about something I tend to go a bit over the top
(If only I had the desire to learn that I have now when I was at school )

Paul

 

[shenion]

The thickness and type of metal sets the needed current.

You want as small a tungsten as needed. That helps keep the arc focused. Too small for the current and the tungsten will overheat. Too large and the arc will wander.

Cup size and gas flow are related to the amount of current. The more current, the more heat so the tungsten needs more cooling.

More current means a bigger weld pool, so there will be a larger area that needs gas shielding, hence a bigger cup.

The cup size and gas flow are related. If gas is too fast for the cup, it will generate turbulence. Too slow and it can easily get blown away.

I use the Miller calculator. Seems everything I do says 1.6mm tungsten and 3/8" cup Just put in a gas lens and have nothad time to try that. Should help as thelast ime I tried aluminum it seemed to get contaminated easily.

 

[HasBean]

Aah, That makes sense, thanks Shenion

 

[gaz_moose]

i didnt think that the gas 'cooled' the tungsten?

 

[fingers99]

To some extent it will -- it even cools those plastic see through tent things that people use to weld Ti.

Here's a point -- some of the stuff I do is very thin -- anyone ever seen a tungsten smaller than 1.6mm?

 

[shenion]

fingers99: I have some 1.0mm (0.040) tungstens

 

[fingers99]

Thanks -- I'll have to see if I can get some: just about everything I do in Ti, stainless or mild is 1mm or less, thinner should help focus the arc better.

 

[shenion]

I picked up a set of 10 electrodes on ebay. was less then $20 if I remember right including shipping.

I just checked an it has 3/32" (2.4mm), 1/16" (1.6mm), 0.040 (1mm) and 0.020" (0.5mm). Red, green and orange tipped.

I don't think I even have collets for 0.020

 

[fingers99]

Yes. I've just seen some 0.040 on US eBay. Very cheap -- I think less than £4 -- for 2% thoriated, but the carriage...............

I'll try and get some locally when I drag my torch in to try and find some gas lenses.

There's some nice stuff on US eBay, like small quantities of Ti rods, that are very tricky to get hold of this side of the pond.

 

[Wozzaaah]

Fingers, are those 0.8mm of mine any use to you? Seems a shame to bin them if someone can make use of them.

 

[fingers99]

I'd love them -- might have to make up a collet or collet adaptor, though!

 

[Wozzaaah]

Weldmet sell 0.8mm collets.
PM me your address and I'll pop 'em in the post next week.

 

[fingers99]

Weldmet sell 0.8mm collets.
PM me your address and I'll pop 'em in the post next week.

You are a star!

PM on it's way!

 

[hotrodder]

Personally i've never had any arc wander issues with 1.6mm tungstens, even welding tiny stuff at 8A or so despite the charts saying otherwise. The published 'upper limits' for a given size are a bit high imo though

Tip geometry has a large role to play, 'sharper' offering better stability, 'blunter' having better current carrying capacity. More info here but bear in mind that a lot of it is aimed at orbital/automated TIG

99% of the time i use a gas lens with a #7 cup, a larger cup allows more stickout (when needed) and usually still offers better gas coverage than switching to a tiny cup, along with a better view.

 

[fingers99]

Yeah, gas lens is on the list!