That question again

[silent-flyer]

Hi,

As a newbie, I am going to ask another often asked question. I have a MIG welder and have used it to weld aluminium before, with varying degrees of success.
I am looking to get a TIG welder, but like so many DIY’ers, am on a tight budget. Having looked at the usual website deals, I am a bit confused at what can do what, and quite frankly the amount of information out there now can be quite confusing. As far as I can see any TIG welder for aluminium, really should be something like an AC machine.
I know like everything, you get what you pay for, but that said, for a DIY user who will not be doing a lot with the TIG on a regular basis, what is the best advice on a welder for aluminium work for a tight budget?

 

[piman]

Hello SF,

have you considered an oxy\acetylene set? I suppose a lot depends on your needs and how much and what you want to weld.

I have a very basic DC scratch start (German made) Tig which I use for stainless, but for every thing else I use gas.

Alec

 

[silent-flyer]

Hi Piman,

Yes I have thought of gas, in fact there is another thread I started at the same time as this one. http://www.mig-welding.co.uk/forum/showthread.php?t=14930

I liked welding with gas when I was younger, and am well aware of the disadvantages and the advantages of the medium. (Although I didnt ever try gas welding ali with my old set).

I would go for gas if it were not for the high costs to have the bottles lying about. (Just 3 years hire on Gas bottles will pay for a lower end TIG). I am mainly looking to weld sheet ali for some projects with the English Wheel that I am looking to work on, but I dont really think that the disposible bottles are the way to go?

I still like the idea of a TIG, but as a light user of both gas and other types of welding, it doesnt warrent spending stupid amounts just to get the best you can get if you are not going to be using it all the time.

Regards,

SF

 

[Arsonista]

You can only TIG weld ali with AC. Buy something with UK spares and service backup. In a rush at the mo, other people will add more detail later. Cheers.

 

[piman]

Hello SF,

you will have a bottle rental with your TIG also.

I know when started looking at TIG sets about three years ago, I ended up buying an ex demo machine which I think with all the bits and pieces, consumables etc came to over £400. Not sure of current prices but AC machines are a bit more expensive I understand.

Alec

 

[busa]

You can only TIG weld ali with AC.

That's not true, Aluminium can also be TIG welded on DC, although the process is difficult to master, as there is no cleaning action from the arc. Unlike conventional DC TIG, the torch is run on DC Positive using a very large diameter tungsten. Cleanliness of the material is absolutely critical and preferred shielding gas is helium.

 

[hotrodder]

Oxy fuel offers a few advantages if you're welding together panels that've been wheeled. Welds are softer and (with enough skill) smaller than sheet Al TIG welds as the flux actively 'cleans' the back of the weld too. Upside is that welds can be planished out with the wheel alone, downside is messing around flux and cleaning it up after welding.

You can weld Al with DCEN (thicker sections) and DCEP (really thin sections) with TIG but neither are practical. Forget aluminium unless you spring for an AC/DC machine.
Oxy fuel is FAR more versatile, TIG far more convenient. For occasional use i guess a lot will depend on whether there's a rent free gas supplier near you

 

[silent-flyer]

Thanks for the info all.

It has given me lots to think about. I was rather surprised to learn that gas welding ali is as neat, if not neater that TIG, and more versatile. The only ali welding that I have seen done personally has been by TIG, but I am aware that gas welding ali has been happening for years....practice... practice... practice I guess.

How good are these new aluminim brazing rods? Are they worth looing at? Do they give as good a weld (mechanically) as the more common pure aluminium rods for Gas welding?

As a sideline, how do you know when you have the temperature of the ali about right? I know from experiance, when you heat ali, it doesnt do anything other than give a slight shimmer before it drops on yer foot in a molten blob that instantly gets ones attention!

I have seen one guy heat ali carefully, then using a matchstick he drew the stick across the ali he was working on, and when the heat drew the mositure out of the stick, it left a snail trail across the ali. He then said it was the right temp to start work. (He was using a TIG).

Sorry if this is rapidly turning into a Gas subject!

Thanks again.

 

[shenion]

I have used the aluminum brazing rods and they work well when used properly. The trick is to stir the weld to break through the oxidation.

Having done gas and TIG, I much prefer TIG. It can do about anything. O/A has an advantage for many non-welding uses.

I use gas torch sometimes. I have an oxy/propane setup that works for brazing (not hot enough for welding.)

On a budget, I'd get a DC TIG and use brazing for aluminum. For many years, brazing was my only option for aluminum.

 

[piman]

Hello Scott,

I have also used the aluminium brazing rods but with gas. Useful, I found, for casting repairs. I don't know how good they would be with butt welds on sheet, particularly thin section?

I haven't tried it with my TIG (DC only), any guide to the set up?

Alec

 

[hotrodder]

The "aluminium brazing rods"... is it just me or are all the manufacturers websites set up like the typical 'snake oil salesman'? Filled with testimonials and videos showing how fantastic and easy to use the stuff is. They bang on and on about how strong the stuff is but it all goes a bit quiet with regards to the chemical composition though...

I know the stuff physically works but if it's soooo good why sell it the way they do? It is fantastic for repairing pot metal castings, i wouldn't go anywhere near an aluminium part with it personally

Finding out the composition of the various brands isn't easy as most of them fill their MSDS sheets with things like 'trade secret'
Most, if not all of 'em are zinc alloys and are brittle (scroll down, describes ductility as 'good' and then gives an elongation of 3%!) compared with nearly all aluminium alloys. They constantly bang on about how the stuff is stronger than the base aluminium (true for many alloys), typically demonstrating this by showing how easy it is to break the aluminium part again without breaking the repair. I wonder if zinc embrittlement (right hand column) could have anything to do with this?

Silent-Flyer,

I woudn't describe oxy fuel aluminium welds as neater than TIG, in most cases anyway, but because the flux actively 'cleans' the back of the weld you don't need to feed filler into the puddle to get complete fusion. With enough skill/practice you can get a weld with less root reinforcement, couple that with a softer weld and oxy fuel welds are more easily planished out. There's an example in this thread, oxy fuel welds are in the post below mine (Aerometalworker). Tinmantech website has a load of info too but is heavily biased towards oxy fuel

As you say, no colour change with aluminium but there are tell tales (need a proper 'flux rated' lens to see past the flux glare). Can't describe it better than you'll get from this site. Don't fall for the hype over that particular torch, plenty of other nice (and lighter) torches on the market too

 

[shenion]

I bought the Alumweld rods from a swap meet. Later saw the infomecial with all the hype.

It came with a video showing it failed miserably. Then showed the steps that were not done properly. At least there was no hype in the instruction video

I have done sheet aluminum many times, mostly 0.090 to 0.125". Worked great. These were R/C mufflers and they have not failed even with the huge thermal stresses.

 

[silent-flyer]

Thanks for the info Scott and Hotrodder.

I find that logical and well presented impartial advice like this worth more than 1000 salesmen put together.
I personally find surfing the net bewildering when it comes to the sheer volume of information on what ever it is that you are trying to find out, and most of it is questionable.

You have helped to steer me in a direction that I think I will go in, and get gas as it is apparent that I am going to have to shell out many hundreds fo pounds for a ac machine, which I will only need on a relatively occasional basis. I am only working on small peices anyway, and am looking to muck about with custom made aircraft parts, control horns, nosecones for old gliders etc.

I eventually want to look at making up a small race car body if I can build my skills up, but it is a long way off...

Thanks very much, all your help has been a breath of freash air, and thanks to great forums like this!

Ta Muchly,

SF

 

[TheJoker]

As a beginner looking to be cheap I tried those brazing rods. I used a butane torch with them and my experience is a bit split. One thing I do know is that it's not for me. I had problem with a) getting the alu-oxide off (lazyness and complicated U-shaped pieces), b) melting the alu when trying to apply the "brazing" (= big goop!). c) When I wanted to grind the brazing into shape it's too hard to file easily and the using a dremel with a grinding stone just cracks it all up as it's so brittle.

I believe that the use of it is good if you're doing simple shapes, got a good torch, and you don't want to grind/file the results. I'm also afraid that it'd vibrate to pieces in my applications (high-revving motorbikes), but shenion does state it should work.

I paid £600 for my used AC/DC TIG welder - a lot, but one can overcome it. As long as it's not broken I can probably get a similar amount back when selling it.

 

[Bsmith]

As a sideline, how do you know when you have the temperature of the ali about right? I know from experiance, when you heat ali, it doesnt do anything other than give a slight shimmer before it drops on yer foot in a molten blob that instantly gets ones attention!

O/A flame turns a pinkish colour just before alu melts.

 

[TheJoker]

All I know is that it turns shiny and you can see your tungsten's reflection in the pool... that's the "GO" signal to me. Let me know if there's a better one.