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Old 12-14-2017, 11:09 AM
rustreapers rustreapers is offline
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Default Pre-stretch before welding for low crown panels.

I am looking for your input for pre-stretching of low crown panels prior to welding where planishing is not possible due to obstructions.
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Old 12-14-2017, 01:53 PM
toreadorxlt toreadorxlt is offline
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If i had to do it, id surely take a calculated approach. Id run a test panel with two witness marks and measure them before and after welding to determine the amount of pre stretch needed. After that was done, Id try to simulate the amount needed until I was confident, and apply that amount to the panels to be welded
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Old 12-14-2017, 07:31 PM
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Richard K Richard K is offline
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RodDoc once showed some snips be used for final trim. The cutting edges of the snips were serrated and so stretched the trimmed edge just a bit. Upon welding the shrink wiped ou the stretch.
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Old 12-14-2017, 09:43 PM
crystallographic crystallographic is offline
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When I was welding up holes in steel firewalls for primo resto work, I gradually came to stretching each hole area first, and would then weld it up. It was funny at first, to see a volcano instead of a sink and warp. I shrunk the metal more after the first couple of tries on those flat trapped panels. I did the same thing with closing panels up on large flat surfaces, stretching first and then welding. It really helped me solve the weld-shrinkage issues on some "closed" work, like welding a big patch in the side of a double-wall Chev van. I'd stretch both edges as equally as I could measure and then weld. I would test first and then go. It isn't an exact science, but it works surprisingly consistently. Stretch about equal to the expected HAZ, depending on filler or no, type of weld, and weld speed.

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Old 12-15-2017, 12:53 AM
Maxakarudy Maxakarudy is offline
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Sometimes I find it's necessary to mig weld under these circumstances
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