View Full Version : welding a shell
is there any paticular reason we use mig when strengthening a shell? imo it would be better to tig it as the weld is more precise and controllable, plus a tig weld has flex in it so can take a bit of abuse unlike a mig run which just cracks with movement.
Because most of the people on here that mig weld their novas do it themself and tig is not easy or cheap
BRoadGhost
08-04-13, 03:02 PM
Sticking metal is sticking metal. You make sound as if TIG is the more accessible option to the masses...
chrisd1986
08-04-13, 03:02 PM
i think its mainly because its easyer to get use of a mig than a tig welder
I don't have the skills for tig,
I don't have a tig set up either,
I can not afford a tig set up and my mig was £50
Simples :)
ok i understand that not the average joe can tig to a decent enough standard. but even if the shell was sent to a bodyshop they seem to mig it, dont think ive ever seen 1 being tig'd.
BRoadGhost
08-04-13, 03:29 PM
Heh, don't be fooled the "average joe" isn't going to set the fabrication scene alight in MIG either
chrisd1986
08-04-13, 03:36 PM
i taught myself how to weld, i bought a mig welder for.£45 got some gas and had a play about in my shed and have been doing it since
Heh, don't be fooled the "average joe" isn't going to set the fabrication scene alight in MIG either
very true indeed, we even have agency lads in work that have the skills of a soggy sponge
Tig welding is to slow
good things come to those who wait
good things come to those who wait
This is true, but also means difference in price
meritlover
08-04-13, 04:02 PM
is there any paticular reason we use mig when strengthening a shell? imo it would be better to tig it as the weld is more precise and controllable, plus a tig weld has flex in it so can take a bit of abuse unlike a mig run which just cracks with movement.
Please explain...
Have you ever TIG welded? please share your experiences...
Please explain...
Have you ever TIG welded? please share your experiences...
im a coded tig welder. ive repaired my front panel with tig but not welded a full shell.
meritlover
08-04-13, 04:15 PM
im a coded tig welder. ive repaired my front panel with tig but not welded a full shell.
as above,
please explain how a MIG weld gives less flex than TIG
the fact you have not welded a full shell explains why there are 2 pages about this subject already. As you will know, TIG on steel which has even the slightest smell of rust, oil, paint etc is a disaster, some parts of the car you can clean up well enough to TIG, others you just cant.
surely the fact that so few issues exist with MIG welding strengthening plates suggest that in this application, there is no requirement to use TIG?
as above,
please explain how a MIG weld gives less flex than TIG
the fact you have not welded a full shell explains why there are 2 pages about this subject already. As you will know, TIG on steel which has even the slightest smell of rust, oil, paint etc is a disaster, some parts of the car you can clean up well enough to TIG, others you just cant.
surely the fact that so few issues exist with MIG welding strengthening plates suggest that in this application, there is no requirement to use TIG?
for example if you tack some thing up with tig and it pulls with the heat you can easily bend that tac to get the steel back where you wanted it (the same applies to mma). if you tack it with mig and it pulls, you have to grind that tack out and reposition it as a mig weld is very hard and brittle and will snap the minute you try bending it.
your very right about the cleaning aspect of things, i suppose it would be more suited to a shell which has just been blasted.
meritlover
08-04-13, 04:32 PM
for example if you tack some thing up with tig and it pulls with the heat you can easily bend that tac to get the steel back where you wanted it (the same applies to mma). if you tack it with mig and it pulls, you have to grind that tack out and reposition it as a mig weld is very hard and brittle and will snap the minute you try bending it.
true, but thats a tack and does not represent the finished weld. During a TIG tack you can heat both sides with the torch and blob a bit of rod (if need be) on to tack.
when you tack with MIG, you rely on a momentary blast of heat, not enough to heat both surfaces, but just enough to leave a tiny drip of wire...hence its weaker
your very right about the cleaning aspect of things, i suppose it would be more suited to a shell which has just been blasted.
yup, even then any blasting dust or grit causes havok with TIG (the grit sort of explodes). Also, any seam where there is dirt between bubbles through and wrecks the weld.
yup, even then any blasting dust or grit causes havok with TIG (the grit sort of explodes). Also, any seam where there is dirt between bubbles through and wrecks the weld.
and that my friend.... answers my origional question :thumb:
true, but thats a tack and does not represent the finished weld. During a TIG tack you can heat both sides with the torch and blob a bit of rod (if need be) on to tack.
when you tack with MIG, you rely on a momentary blast of heat, not enough to heat both surfaces, but just enough to leave a tiny drip of wire...hence its weaker
just read something on an american hotrod site that said they tig their chassis for this exact reason, and if tig isnt possible they mig it then heat treat it.
meritlover
08-04-13, 04:47 PM
i dont know why they would heat treat after?! it only becomes a problem during the tack process as the heat blob of molten wire is sitting on the surface of two cold plates with no penetration.
during a bead of MIG, as you chase it down the joint, there is enough heat to get penetration and hence a weld is formed.
i dare say an American hotrod is an ideal place to TIG as about 90% is fabricated stock steel anyway with 10% of original parts sat on top of it.
its not like changing a Nova sill on your mums car port with a TIG.
BRoadGhost
08-04-13, 07:10 PM
I suspected this topic might go this route; there needs to be a thread now about why textured bog paper isn't superior to conventional flat.
Fact is what should really be asked is why aren't more people wiping their own bottoms properly?
I suspected this topic might go this route; there needs to be a thread now about why textured bog paper isn't superior to conventional flat.
Fact is what should really be asked is why aren't more people wiping their own bottoms properly?
Quilted is my personal choice with a touch of alo-Vera
The burning question is,,,,,,,,,
Can you wipe with your left hand if your a righty? I'm not brave enough to try incase I get it wrong :(
In my eyes and experience, most welding is MIG for ease and speed. Working in a bodyshop, laying under a car, using a foot pedal isn't gonna be possible...
Where as a Mig you can use anywhere..
I was discussing this with someone a while back and we decided brazing would be a very good idea.....
Nick.
meritlover
08-04-13, 08:17 PM
I was discussing this with someone a while back and we decided brazing would be a very good idea.....
Nick.
what on earth brought you to that conclusion?
what on earth brought you to that conclusion?
It's strength.... Not a good idea then? We were actually thinking just the engine bay not the full shell etc.
Nick.
meritlover
08-04-13, 08:29 PM
its not necessarily stronger. There are advantages in body work repair in that the temperature is lower, but you would need to joggle the faces as a butt-braze would be nearly impossible.
Gas welding might be better than brazing, but pretty much provides the same process as TIG. it might be a bit more forgiving in the sense that it will burn off a lot of contamination before you crank up the heat and start welding.
We are talking about 3 (or more) processes of joining metal here in 3 (or more) situations and will become confusing. There will be no outright winner, but each have their own advantages and disadvantages in each case.
Conad will be able to offer more experience than me, as he is the 'coded' welder.
its not necessarily stronger. There are advantages in body work repair in that the temperature is lower, but you would need to joggle the faces as a butt-braze would be nearly impossible.
Gas welding might be better than brazing, but pretty much provides the same process as TIG. it might be a bit more forgiving in the sense that it will burn off a lot of contamination before you crank up the heat and start welding.
We are talking about 3 (or more) processes of joining metal here in 3 (or more) situations and will become confusing. There will be no outright winner, but each have their own advantages and disadvantages in each case.
Conad will be able to offer more experience than me, as he is the 'coded' welder.
Our main idea was its strength and the fact it less heat is required so things are less likely to warp. When the time comes it may be an avenue we go down with my own engine bay prior to putting in a big block motor. Every day is a learning day though so I'm happy to hear others input. ;)
Nick.
therealnovaboy
08-04-13, 08:49 PM
Stick welder is the best.
Stick welder is the best.
Canny beat a good old Oxford Bantam :)
Working in a bodyshop, laying under a car, using a foot pedal isn't gonna be possible...
doesnt need to be a pedal, we've got some nice torches in work with rollers on the grip.
Conad will be able to offer more experience than me, as he is the 'coded' welder.
cant help but feel you've got a problem with me. you're obviously very knowledgable in what your talking about so cut out the animosity.
as far as brazing is concerned, your not actually fusing the materials together, just addding a material that will stick them together... like gluing it.
meritlover
08-04-13, 09:39 PM
cant help but feel you've got a problem with me. you're obviously very knowledgable in what your talking about so cut out the animosity.
as far as brazing is concerned, your not actually fusing the materials together, just addding a material that will stick them together... like gluing it.
Not at all in fact, on the contrary. Iam not a 'coded' welder and therefor cannot back up any of my comments from anything other than self learned experience...which i always offer freely to the intended benefit of others. Im not here to step on the toes of people who are officially competent and certified and was hoping they could deliver some evidence and science to what i have to say.
brazing is just like soldering.
well..... you were spot on lol :thumb:
meritlover
08-04-13, 09:48 PM
well..... you were spot on lol :thumb:
Phew!! there's a first time for everything.
but...
didnt you start this thread?
i did yeah, was basically wondering if anyone knew of a particular reason nobody tig'd the shell, or peoples views on it. bit by bit it got answered lol
therealnovaboy
08-04-13, 10:05 PM
Some people do tig shells
meritlover
08-04-13, 10:07 PM
some people dont TIG shells.
therealnovaboy
08-04-13, 10:09 PM
If everybody tig welded shells you'd probably ask why nobody Mig welds shells
If everybody tig welded shells you'd probably ask why nobody Mig welds shells
lol
w_wall_2001
09-04-13, 10:51 AM
we could argue all day with weld strength etc of the various process's, but most shells are thin wall material to start with so welding will in fact strengthen the shell. without proper mechanical tests this could go on forever (which wont happen). thats my 2 pence worth.
will
oh i've done my fair share of 'destruction tests' on novas in my time lol
w_wall_2001
09-04-13, 11:01 AM
ha ha i havent done that for a while but my life is hounded with stupid mechanical tests and procedures with work
quality inspector???.... rich boy lol
w_wall_2001
09-04-13, 11:06 AM
client qc inspector for allseas engineering but they throw all the ndt rubbish my way too lol
Jon_nova1
09-04-13, 06:46 PM
Being a coded welder i wouldn't have thought you'd need to ask this question?
Mig replaced arc due mainly to it's quicker running times, tigging takes around 3 times longer and you have to do alot of surface prep work, so your talking atleast 3 times the price.
Mig welds are not brittle and you can bend around a spot weld etc, it's cold fusion on the surface your welding to that gives the impression it's weak, since tig requires all weldable surfaces to be hot to actually be able to tack, this problem doesn't exist, a completed mig run will be stronger than the steel itself...if you can weld.
You also need to get rid of rust and any surface contaminents, i don't think anyone would be impressed if they had to pay £1K+ just to have a sill welded in because the welder had to clean off all the crap, grind all the rust away then wire brush everything that's going to be welded (including comtaninents on the inside of the weld and anything that will bubble through) when it can just be migged and the welder just takes a sanding pad to the area's to be welded
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