Arc, Tig Or Mig ?

[Jay]

I Am Going To Attempt To Teach Myself The Fine Art Of Welding And Am Looking Around At Different Welders.

Can Anyone Give Me Any Info On Which Would Be A Good Choice, I Need Something Usable At Home, But Man Enough To Weld My Bike Frame And Not Fall To Bits.?

Appreciate Your Advice!

[Pennywise]

mig if your looking cheep, tig if you wanna be serious about welding, arc if you wanna laugh

[dracken1]

i agree with pennywise.
but dont class mig and cheap as to mean not sutible.

mig is the perfect tool for a beginner admittedly tig gives you more control.
but will take a novice longer to master than mig

i personally detest the gasless machines.
but unless you want splattery welds you will need to use an argon/co2 mix
gas.
it will cost you to open an account for the bottles.
used to be that you could borrow a mates spare bottle but these days it's nothing to get a supprise visit from boc/airproducts.
and woe betide you if you can't show them the correct number of bottles registered to you. (i know)

get a mig, buy the the most powerfull one you can afford.
a small dc tig will cost you about the same as a medium sized mig.

but if you want to do ali then you'll need a switchable machine which can really hit the housekeeping hard

[Blackjack]

If you go to a welding supplier, you can sometimes pick up usedsingle phase industrial MIG welders that they've taken in part ex on new units.

Two things make this a good idea. First of an "proper" one will have longer duty cycles, better arc stability, and just generally be nicer to use than a "hobby" welder. Normally things like tips and liners will be a lot cheaper too, and since you bought it from a commercial welding supplier I'm pretty sure the wire will be cheaper too. I've always found that an industrial machine performs better on thin stuff like mudguards and tanks.

Secondly it's already second hand, so if you decide it's not for you then you have a good chance of getting back what you paid for it.

Look for something about 160-180 amps, and you'll find it will do most things.

[Pennywise]

quote from above
"but if you want to do ali then you'll need a switchable machine which can really hit the housekeeping hard"

how do you mean a switvhing mig?


ive got a clark weld 150te and ive tried welding ally wit hit to varing degress of success.

when using gas you have the earth in the earth and the lead in the positive

when god forgive you want to use it gassless you have to have the earth in the positive and vicea versa

is this what you mean by switching?

also, i found an old oxy bottle, and i painted it to look like an argon shield heavy bottle, took it to my local metal yard, and they have a service "like for like"...in fact if you ask around you will always find some one who will exchange a bottle without a contract....I dont know how much it is from boc, by McGovans in harlesdan is £23 exchange, and haywoods here in wrexham its £41 exchange.....

a bottle usually lasts me a year, and im welding trucks, bikes,cars, numerous projects, and it just seams to last forever

and you are just as well to weld gassless, than you are with pub gas, cause pub gass is poop.

[dracken1]

a dc (direct current) tig will weld most metals
but for ali you need an ac (alternating current) machine

theres quite a price difference between a dc and an ac machine

[Pennywise]

mmmm...ok...but mine did weld ally......i realised that i had the 6mm roller but the 8mm wire, and that didnt hepl....but i was also not welding clean ally....even though id ground it clean...apparently you have to clean the ally with a cleaner

what cleaner do i need?

also, its a truck sump im welding....does oil saturation hinder ally welding?, and if so, what do i combat it with?

[dracken1]

ah you were welding ali with a mig!!
i've tried that, it is not easy to get a decent finish .

as for the other questions i'm no expert with ali.
ask blackjack :)

[Pennywise]

i dont care about a decent finnish, all i car about is an oil tights weld on the sump...the bugger holds 4 gallons, an i wouldnd like to deposit all that on my drive:)

http://www.granadaclassics.com/rust1.jpg

[Pennywise]

sounds like i need to get some 1 inch angle and make a new flange, and just weld me up a steel sump:)

[Blackjack]

I've got a big old fashioned 300 amp TIG. As long as your sump is close to, or over, 1/4" thick I can probably weld it for you by "floating" the oil contamination on top of the weld pool.

This is only really possible with a water cooled torch and a LOT of amps as you need to do it in one pass. Anything much thinner than 1/4" won't let you get enough heat into it to float the contaminants on the pool without collapsing in a heap of molten ally. And even then there are no guarantees.........

[Pennywise]

scary.....i think ill just make my own out of steel....where ive had to unbolt the spring hangers and slide em forward 9 inches, so that the wheels of the truck are in the middle of the arches , ment i had to slide the axle under the engine........in fact a bit more weight to the engine will help compensate loosing almost 1.5 toones of dennis fire engine cab:)

BTW, if you ever in the situation, where you are pushing a fire engine onto your drive with no brakes.....a seat belt tied round the rear axel, and to the front of you citroen xantia....just doesnt work

http://www.granadaclassics.com/oopse4.jpg
http://www.granadaclassics.com/oopse1.jpg

[Sir Ewok]

The reason you need AC current to weld ally is simple. If you have ever broken an ally part you will notice that it oxidizes almost instantly. When welding, this is exactly what happens. When welding ally with AC, one pulse produces the heat for the weld, the negative pulse pulls the oxidization of the heated parts. If you use DC current, you lock the oxidization into the weld, creating a weakness in the welded area.

[Jay]

Thanks for the advice guys. I have got myself a MIG on the basis that it was reasonably priced and most people seem to think it's a nice easy way of starting off...if there is such a thing.

I am only looking to do some small stuff to start with, a few brackets for my bike really. I could no doubt have one of the boys in the workshop make anything I need but that isn't as much fun........he says.....BEFORE he has even had a go.

[Peirre]

The reason you need AC current to weld ally is simple. If you have ever broken an ally part you will notice that it oxidizes almost instantly. When welding, this is exactly what happens. When welding ally with AC, one pulse produces the heat for the weld, the negative pulse pulls the oxidization of the heated parts. If you use DC current, you lock the oxidization into the weld, creating a weakness in the welded area.
when I was an aprentice welder, they told me the reason you must use AC for welding aly is that the surface oxide melts at a far higher temperature than the aly itself.
the AC makes the surface oxide shake off allowing you to weld the base material, making for a cleaner / stronger weld. Note, generally the gas mix used for comercially welding aly is slightly diferent than the 1 used for welding steel. and a word of caution, I have had more sever electric shocks off an AC welding set than a DC set (once being blown across a room 20ft)

[dracken1]

I have had more sever electric shocks off an AC welding set than a DC set (once being blown across a room 20ft)

oh yes i hear that :eek:

[MrFluffy]

Ive had reasonable oil tight alloy welds with a mig using a argon mix on a cebora 130 (snap on) mig. I know it was tight because it was a plenum chamber (actually about 1/4 ally sheet coincidentally) and we pressure tested it after. Ive done other bits and bobs with it too, but Id shy away from stuff that my life depended on (brake mounts on forks etc)...
They sell argon refils in the diy shops over here (france)... Its only 500L tho, I just take in the old cylinder and they give me a new full one. And I agree pub gas is awkward to use compared to argon, but if your doing mild steel sheeting on some old car or the like its better than wasting the good stuff. I used to get my pub gas refilled at a local calor depot who had a exchange service and im sure i seen argon cylinders there too. You have to have a messers cylinder to use theirs tho, and fortunately the magic supply co had come up with the right one. Its just ran out and im now scratching my head where I can get it filled local, it may have to come to uk on holiday to a calor depot :)
Another thing is find someone who can weld, I did a welding course at college and stuff, but never got on with my mig at first, I just put it down to a crap welder after the good stuff at college. A welder friend with the same sort of kit came to visit and he told me it was terrible (which I knew anyway, helpful git!) , then shortly after the bottle fell over and smashed the regulator, and after replacing it, it welded like a dream...
One last thing I bought two regulators and I ALWAYS wind it back out after a session on the argon, just too expensive to leave it for a few weeks to find you had a leaky shut off valve and saves peeing round, have rapid push fit connectors on the regulators so I can just snap on the cylinder suitable for the job in hand...
Having said all that, Im shopping round for a nice old 3 phase tig, as I have the luxury of 3 phase in me shed, and Im about to start building a new tube chassis for my car (burn the heretic!), he says eyeing that old pickup cab with a nice v8 ;)

[Blackjack]

Never gave it much thought, but I'm assuming the leaky sump is cast? Welding sheet (or billet) ally isn't a problem if it's been soaked in oil, the problem lies in castings (mostly sand cast, die cast is a lot better) which tend to be porous.

Try "cooking" a set of perfectly clean pre unit Triumph crank cases prior to fitting the main bearings in your mother's brand new gas oven, and you'll soon find out just how much oil a casting can retain (bloody lucky I put a baking tray in there!!!).

Mr.Fluffy there is a possibility I may be selling my BOC ADR 300 split phase TIG, with a Tweeco water cooler at some point in the future (thinking about getting an inverter set up). And thinking about it I may know for another one if he hasn't sold it already. This would be in Bristol.