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Old 05-10-2010, 02:14 PM
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Cutting through two body panels at the same time?

I am helping a friend put patch panels over some rusty wheel wells on a 1950 sedan. I was thinking about placing the new panel over the old one and cutting through both at the same time.

Is this a bad idea? If not, what can I use to cut them out that will leave a small (tight) gap to butt weld back? I don't want a wide gapped loose fitting panel to weld back.

Thanks.

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Old 05-10-2010, 02:54 PM
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Quote:
Originally Posted by ck 2
I am helping a friend put patch panels over some rusty wheel wells on a 1950 sedan. I was thinking about placing the new panel over the old one and cutting through both at the same time.

Is this a bad idea? If not, what can I use to cut them out that will leave a small (tight) gap to butt weld back? I don't want a wide gapped loose fitting panel to weld back.

Thanks.
For butt welding it works great. Use a 1/32" cut off wheel, make sure you have it EXACTLY where you want it and cut away.

Brian
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Old 05-10-2010, 04:26 PM
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1/32 wheel on an air grinder?
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Old 05-10-2010, 04:37 PM
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cutting 2 panels??

NO,i would cut the old panel exactly where you need to cut the new one.maybe draw a line on panel with an AWL,cut a little big,and grind to line,then put either piece of old panel over new panel,tape them together (or C clamp them)again scribe a line with the AWL, cut a little larger,then grind to line.MEASURE A bunch of times,only cut 1 time. we use the 1/32 nd cut off wheel,on a 4 inch elec grinder, HF has discs and elec grinder (not a very good one though)or HD sells some good ones (more expensive though) have fun
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Old 05-10-2010, 04:44 PM
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Quote:
Originally Posted by ck 2
I am helping a friend put patch panels over some rusty wheel wells on a 1950 sedan. I was thinking about placing the new panel over the old one and cutting through both at the same time.

Is this a bad idea? If not, what can I use to cut them out that will leave a small (tight) gap to butt weld back? I don't want a wide gapped loose fitting panel to weld back.

Thanks.
Check out the 5th post in this link...

http://allshops.org/cgi-bin/communit...9990202483912&

The Panel_cut_and_fit.doc gives a pretty good diagam of what he is talking about. I would never have thought about cutting on an angle - but I tried it and it works. Curves are a *****.
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Old 05-10-2010, 05:30 PM
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I couldn't get the link about the angle to open. What does he do hold his wheel at an angle to cut on a bevel instead of a straight cut?
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Old 05-11-2010, 07:09 AM
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Quote:
Originally Posted by ck 2
I couldn't get the link about the angle to open. What does he do hold his wheel at an angle to cut on a bevel instead of a straight cut?
I converted the .doc (Word) file to .pdf and attached it, might be easier to open. Credit to Rog02 at Metal Shapers Assoc. - allshops.org.

I use a 3" air grinder which I grip with my right hand, and then I support my right hand with my left - somewhat like a golf club grip. It works pretty well for straight cuts but can be a bit tricky on curves.

I dont have any clecos yet, so I use small self tapping screws to hold the panel in place while I am cutting.

Hope this helps.
Attached Files
File Type: pdf Panel_cut_and_fit.pdf (12.2 KB, 67 views)
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Old 05-11-2010, 07:32 AM
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You are right Bob, that is the best way to do it. But when I want to make one of those perfect butts I use offset tin snips for a flawless cut up to the line. I use the cut off disc to rough cut it about a quarter inch from the line then the offset tin snips for perfection.

Brian
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Old 05-11-2010, 08:03 AM
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i mark , cut and fit . i keep old speaker magnets to hold the pieces in place while welding.
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Old 05-11-2010, 08:04 AM
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Actually it's easier just to use an air saw with a 24TPI blade, nice clean cut and curves are no problem. An exact match every time.

The air space should be equal to the metal thickness of the panels

Use the butt weld clamps, start at the top-center and work around from there.

Metal warping is not a problem IF there is no stress to the panels. DO NOT clamp down the panel into place, it should just fit into place naturally.

.017 or .023 wire is easiest to use for butt welding. You will be literally welding into thin air SO you will be welding into the puddle, letting it flow into the panels. Start at the tack beads and make the puddle flow.

Practice, practice, practice : up, down and sideways to get the feel for it.

Let the welds cool naturally, DO NOT air quench or water quench, that's called shrinking for a reason. Quenching WILL warp your panels.

Have fun with it, once you learn it you'll know it for life.
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Old 05-11-2010, 08:13 AM
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Quote:
Originally Posted by shine
i mark , cut and fit . i keep old speaker magnets to hold the pieces in place while welding.
I use hard drive magnents.. hold a lot stronger. just can't get them too hot or they loose magnetism
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Old 05-11-2010, 09:09 AM
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Quote:
Originally Posted by oldBodyman
Actually it's easier just to use an air saw with a 24TPI blade, nice clean cut and curves are no problem. An exact match every time.

The air space should be equal to the metal thickness of the panels

Use the butt weld clamps, start at the top-center and work around from there.

Metal warping is not a problem IF there is no stress to the panels. DO NOT clamp down the panel into place, it should just fit into place naturally.

.017 or .023 wire is easiest to use for butt welding. You will be literally welding into thin air SO you will be welding into the puddle, letting it flow into the panels. Start at the tack beads and make the puddle flow.

Practice, practice, practice : up, down and sideways to get the feel for it.

Let the welds cool naturally, DO NOT air quench or water quench, that's called shrinking for a reason. Quenching WILL warp your panels.

Have fun with it, once you learn it you'll know it for life.
You said a mouth-full, ESPECIALLY about cooling the welds. This is without a doubt one of the biggest, if not THE biggest urban myths of autobody. Cooling hot metal causes it to SHRINK. Shrinking causes warped panels, PERIOD, end of discussion.

Can you "control" metal movement by carefully cooling, yes. HOWEVER, this takes a LOT of experience. The simple basics is, cool hot metal, shrink, warp, BAD, no-no.

But on the gap, this is an opinion, personally, ZERO gap is best according to every tin man I know. I weld butt welds (I am miles from a "tin man") with ZERO gap. I have a book where the guy even measures the metal before and after welding and the larger the gap the more shrinkage occurred.

But again, depending on how it is welded it could make a big difference or little with or without a gap. It is largely preference.

I personally don't like the butt weld clamps, just don't. I use large vice grip C clamps ( I have a couple of two foot deep ones). The magnets sound like an interesting idea. I have heard it many times but forget and never try it.

Brian
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Old 05-11-2010, 07:06 PM
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"You said a mouth-full, ESPECIALLY about cooling the welds. This is without a doubt one of the biggest, if not THE biggest urban myths of autobody. Cooling hot metal causes it to SHRINK. Shrinking causes warped panels, PERIOD, end of discussion."

Thank you Brian, it's evil twin is "Hammer Welding":

1) sheet metal is a 3 dimensional object, it has CUBIC volume. If you hammer down the weld the metal must go somewhere, that's called stretching the metal, making an oil can that's a bear to remove.

2) with steel, if it has cooled below cherry red but still too hot to touch, hammering will induce stress fractures, (metal fatigue, work hardened). If the welds need to be hammered, wait until it's room temp.

Yes, bodymen have always had a warped sense of humor.
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