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#11 Re: Panel Work- Welding question
B210sleeper Posted on: 2006/11/21 7:33
flux core wire is probably going to make it really hard unless you have a good one with current and feed speed, which if you did probably could tig also.

i've learned my lesson no MIG on sheetmetal! ( of not unless you got a really good one,etc..)

I'd use the MIG for quick little things like making a grille or things out of 1/8" stock, mine's no good on thinstuff, and it overheats if you really get welding...


#12 Re: Panel Work- Welding question
pager Posted on: 2006/11/21 9:57
Hey this is a very informative thread good work!
I have heard important things in choosing a MIG welder are:-

duty cycle. More info

detachable handle. Cheaper and easier to replace inner sleeves once they get dirty (i recon just dont let dustetc get into the machine and onto the wire)

Wire size.More info plus a few interesting points

cheers


#13 Re: Panel Work- Welding question
Coops Posted on: 2006/11/21 10:24
Quote:
mig is the way to go as oxy will produce too much heat and distord the metal


I agree, but panel beaters were using oxy / acetalyene for a long time before migs were around.

Yes - You have to be more careful about how much heat you put into the panels, but as a cost effective option, you can certainly get good results from an oxy set.

Judge for yourself: -

From this - Open in new window


To this - Open in new window


And finally, this - Open in new window


All using an oxy set.


#14 Re: Panel Work- Welding question
woody Posted on: 2006/11/21 10:40
ive got a lot of holes in my coupe im just wondering for the bigger ones should i cut a rough circle and weld it on then grind the weld or just try to fill the holes?


#15 Re: Panel Work- Welding question
B210sleeper Posted on: 2006/11/21 10:49
oxy + brazing. will work just fine.

in highschool shop i used to braze thin sheet to thick walled pipe and bar stock to make oil lamps and random stuff. use a small tip.

if you look the frame is brazed together - it's actually stronger than the steel it's holding.


I could be wrong, but that's hat i've seen and experienced myself.

the brazing is more brittle than the steel. more or less brittle than a weld? dunno...


#16 Re: Panel Work- Welding question
Cable_Tie Posted on: 2006/11/21 11:29
For small holes. . .

Put some copper behind the hole.

Weld from the front.

Grind and done!

The weld will not stick to the copper, it supports the molten blob.

I use a bit of 1/2" copper pipe bashed flat. . .

Try it, you will be surprised


#17 Re: Panel Work- Welding question
Daveman Posted on: 2006/11/21 11:53
if you look the frame is brazed together - it's actually stronger than the steel it's holding.

the brazing is more brittle than the steel. more or less brittle than a weld? dunno...


There is no way the brazing is stronger than the material it's joining. Brazing doesn't penetrate like a steel weld and shouldn't really be used to take loads. They would have used it from the factory just to join panel skins together like from the roof to the pillars. I think our datto's have lead brazed joints in the tops of the pillars.


#18 Re: Panel Work- Welding question
B210sleeper Posted on: 2006/11/21 12:11
I am partially correct. a tig would be best.

from : http://en.wikipedia.org/wiki/Brazing

...Common brazements are about 1/3 as strong as the materials they join because the metals partially dissolve each other at the interface and usually the grain structure and joint alloy is uncontrolled. To create high-strength brazes, sometimes a brazement can be annealed, or cooled at a controlled rate, so that the joint's grain structure and alloying is controlled...

Brazing strength - joint geometry - Brazing is different from welding, where even higher temperatures are used, the base material melts and the filler material (if used at all) has the same composition as the base material. Given two joints with the same geometry, brazed joints are generally not as strong as welded joints. Careful matching of joint geometry to the forces acting on the joint, however, can often lead to very strong brazed joints. The butt joint is the weakest geometry for tensile forces. The lap joint is much stronger, as it resists through shearing action rather than tensile pull and its surface area is much larger. To get braze joints roughly equivalent to a weld, a general rule of thumb is to make the overlap equal to 3 times the thickness of the pieces of metal being joined...

Advantages over welding

The lower temperature of brazing and brass-welding is less likely to distort the work piece, significantly change the crystalline structure (create a heat affected zone) or induce thermal stresses. For example, when large iron castings crack, it is almost always impractical to repair them with welding. In order to weld cast-iron without recracking it from thermal stress, the work piece must be hot-soaked to 1600


#19 Re: Panel Work- Welding question
Daveman Posted on: 2006/11/21 12:16
Heh, you're supposed to delete the reference to wikipedia and pretend you came up with all that!


#20 Re: Panel Work- Welding question
B210sleeper Posted on: 2006/11/21 12:22
lol that would be silly, then i'd have to go back and edit my first post so it is correct and then rant about it...

I went and looked it up so i know what's right.

I think it's ok to fix rust outs brazing if you follow procedures and have no other options.

don't braze your rollcage, frame, or other load bearing structures.

...brazed joints are generally not as strong as welded joints. Careful matching of joint geometry to the forces acting on the joint, however, can often lead to very strong brazed joints...
{which means don't engineer if you're not up to doing your research..}

now if someone made some sheet metal flares, that would be the way to attach em.



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