Plasma Cutter for auto body work - warpage

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PostPosted: Tue Dec 07, 2021 12:11 am
I am relatively new to the auto body world and am starting body work on my 1986 C10 restoration. I need to cut some rust spots out of the fenders, replace rocker panels, etc, and was wondering if it is better to use a plasma cutter vs an angle grinder. I've watched many instructional videos and have use angle grinders in the past but never seen anyone use a plasma cutter on body panels. I understand they are great for heavy metals, 1/4 or 1/2 inch metal, but what about body panels? Is there warpage from the heat of the plasma cutter? I understand having good technique and good consumables, dry air, etc are all part of getting a nice cut, just wondering why most auto body techs still use angle grinders and saws to cut sheetmetal and not a plasma cutter. There must be a reason, and I wonder if it's warpage? Any help would be appreciated.



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PostPosted: Wed Dec 08, 2021 9:21 am
I use them. Not all the time, but when they are the best choice. They are so fast, accurate, and clean cutting. I've even stuck a patch panel over a rusted out panel, and cut through both at the same time, and had a perfect fit to weld up. But, the plasma "spray" is extremely hot, and contains bits of metal, so there are lots of circumstances when you do not want to use one. Flammables in the area, even undercoating, interior materials, or glass, etc. No masking will protect them except a welding blanket. They can be a bit dicey when cutting double panels, if the second panel is not close up, or right under the top panel, The "spray" can bounce back at you, instead of going through the second layer.



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PostPosted: Wed Dec 08, 2021 1:25 pm
@Chopolds, so is there any warping from the heat of the cutter? Then on top of the heat from the plasma cutter, you let the metal cool and then weld it adding high heat again to the same edges, I wonder if all the extreme heat from both the plasma cutter and welder would cause any warping issues. I know some body filler over the welded area would clean most of that up, but I have never used a plasma cutter before and wonder how hot the metal around the cut actually gets. I very rarely cut heavy metal and if I did, I use a torch to do a rough cut then clean up the cut with a bench grinder and a plasma cutter would definitely speed up that process, but for body panels with thin metal, I just worry I would revert back to an angle grinder with a cut-off wheel to do my cuts and never get my money's worth out of a plasma cutter. Just trying to justify the money for a plasma cutter and if it's worth it for body work.



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PostPosted: Wed Dec 08, 2021 6:52 pm
I have a Plazma cutter and I am still hesitant to use it on body panels accept for initial big cuts. Not because of heat though just I cant get a razor sharp edge with it. Might be because of my set up or I just don't have enough time behind it.

I prefer a Body saw to this day when cutting panels for patches. even elcheapo Harbor fright specials are almost surgical. You can get a really nice edge and fit up with a body saw.
A heck of a lot better than a Die grinder and a cutting wheel.

https://www.harborfreight.com/professio ... q3EALw_wcB

Lots of mfg make them you don't have to get an elcheapo from H/F
i am looking at upgrading mine to a better brand mfg myself.
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Thu Dec 09, 2021 8:42 am
The plasma cutter doesn't put enough heat into the metal to warp it. But welding does, no matter how you try to cool it afterwards (not a good idea). Even paint surrounding the cut area isn't toasted too much, maybe 1/4 to 1/2 inch.



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PostPosted: Thu Dec 09, 2021 9:48 am
chopolds wrote:The plasma cutter doesn't put enough heat into the metal to warp it. But welding does, no matter how you try to cool it afterwards (not a good idea). Even paint surrounding the cut area isn't toasted too much, maybe 1/4 to 1/2 inch.



I agree, Its not the heat with the Plazma cutter.

And Yes as Chop says do not cool weld beads after welding no blowing air on welds, no wet rags, Forget 98% of the You Tube videos you've seen promoting these bad practices just let your welds air cool slowly is best.

Welding and some Heat distortion is normal and unavoidable Hammer and Dolly work will always be required.
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.

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