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# Thread: 1/8 side + 1/8 other = 1/4 penetration ???

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## 1/8 side + 1/8 other = 1/4 penetration ???

I see the machines for alum rated for 1/8.
If I am welding 1/4 alum bar and do one side 1/8 -
weld around on the other side for an 1/8 -
doesn't that equal a one pass 1/4 inch weld on just one side ?
What is the difference structurally or in practical terms ?

dumb question - but seriously.
Thanks, Stu
Last edited by Stu Miles; 12-18-2012 at 03:34 PM.

2. ## 1/8 one side + 1/8 other side = 1/4 penetration ?

Maybe I'm looking at this wrong or over complicating it but I don't quite understand the question are you saying welding two 1/8 pieces together to equal 1/4 inch?

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Originally Posted by Rezeppa
Maybe I'm looking at this wrong or over complicating it but I don't quite understand the question are you saying welding two 1/8 pieces together to equal 1/4 inch?
If machine only does 1/8 inch penetration on aluminum,
and lets say I am welding 1/4 inch aluminum plate.
I do one side and flip it over -
is that doing the same thing as one pass with a machine rated for 1/4 inch alum ?

Thanks, Stu

4. Originally Posted by Stu Miles
If machine only does 1/8 inch penetration on aluminum,
and lets say I am welding 1/4 inch aluminum plate.
I do one side and flip it over -
is that doing the same thing as one pass with a machine rated for 1/4 inch alum ?

Thanks, Stu
I am curious as to what machine you are thinking gets 1/8 inch penetration on aluminum cause for \$1000 you are not going to get a machine that even comes close to that.

And when the size of a fillet weld is measured, it is measured from the leg to the toe and the effective throat is what actually means anything.

I think you may be misunderstanding the ratings for these machines. When they say 1/4 inch, that means that is the max. thickness of base metal for a single pass weld.
Last edited by jpence38; 12-19-2012 at 06:36 AM.

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What kind of machine and what process? You can kind of get away with it on steel, but aluminum is a bit more unforgiving. Because of how conductive aluminum is, it conducts the heat of your weld away very fast, requiring more input amps to keep the heat high enough to weld.

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Originally Posted by walker
What kind of machine and what process? You can kind of get away with it on steel, but aluminum is a bit more unforgiving. Because of how conductive aluminum is, it conducts the heat of your weld away very fast, requiring more input amps to keep the heat high enough to weld.
Well I guess that is why I am asking - cart before the horse maybe -
because I am try to figure out if I can get away with a smaller machine
to weld 1/4 inch plate from two sides.
I am trying to figure out what machine to spend \$1000. budget on.
Realizing I'd have to also get spool gun and Argon with other \$.

Thanks, Stu

7. Depending on what you are welding you could always bevel it. So if it's 1/4" thick grind a bevel leaving a 1/8" land or slightly less & weld it up. This should give you plenty of penetration.

On another note aluminum bridges easily so it is very easy to have a great looking weld with almost no penetration.
Last edited by MMW; 12-18-2012 at 05:33 PM.

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## thanks

Originally Posted by MMW
Depending on what you are welding you could always bevel it. So if it's 1/4" thick grind a bevel leaving a 1/8" land or slightly less & weld it up. This should give you plenty of penetration.

On another note aluminum bridges easily so it is very easy to have a great looking weld with almost no penetration.
Thanks - That helps - and it helps me understand the purpose a bevel serves.
Really appreciate the help.
Stu

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Bevels, or, i call them weld preps are very important. I do very little aluminum so the other guys can fill you in, but with steel, they are generally used on any thing .250 and up. If you are looking at a machine with a rating of 1/8", and thinking mig, a welder that runs on 110 volts is what to expect. Do your self a favor and dont buy some cheap chinese welder, get one made in the usa

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Originally Posted by walker
Because of how conductive aluminum is, it conducts the heat of your weld away very fast, requiring more input amps to keep the heat high enough to weld.
+1

Aluminum is almost 5 times more thermally conductive than steel. That means the heat "leaks away" from the puddle into the surrounding metal almost 5 times faster in aluminum than in steel. So it's almost like a race where you're "chasing the heat." To weld aluminum, you need a machine with enough power to dump enough heat into the puddle faster than it can "leak out" into the surrounding metal.

If your welder has trouble putting out enough heat to "keep up," you can preheat the surrounding aluminum with a torch before welding, and that will reduce the "chilling effect" that it has on the puddle. Just be careful – unlike a similar-sized piece of steel, the entire piece of aluminum will get hot as heck and stay hot longer than you might expect.

In general, for welding aluminum, you want as much horsepower as you can afford.
Last edited by Helios; 12-19-2012 at 03:36 AM.

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