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Cupping, oil canning, potatoe chipping

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Cupping, oil canning, potatoe chipping

Postby WildWestWelder » Wed Jan 31, 2018 1:25 pm

Ok that about covers it. :)

Material 1 pc. 1/2"T x 8" x 8" 3" sq. tube 1/4 wall Both HRS

I am welding the 3" tube center of the 1/2 plate. First time I set the tube center and welded and it cupped at the corners about 3/16". So somebody said cut a hole in the center of the 1/2" so I machined a 2-1/2 sq. hole thru it, centered the 3" tube a welded. It still oil canned about the same. Any remedies? BTW, the 1/2" was flat prior to welding.
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Re: Cupping, oil canning, potatoe chipping

Postby MinnesotaDave » Wed Jan 31, 2018 2:52 pm

One solution is to put a thick washer under it and clamp down the corners to pre-stress it away from the direction it will pull after welding.

Then welding will pull it straight.

Another is to heat the opposite side after welding and let it heat shrink into position.

A third is to do two at once, clamped back-to-back. This way they pull each other straight.

Here is a great old video on "Mr. Shrink."

https://www.youtube.com/watch?v=2vuGlcbDwKY
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Re: Cupping, oil canning, potatoe chipping

Postby aland » Wed Jan 31, 2018 3:35 pm

MinnesotaDave wrote:Another is to heat the opposite side after welding and let it heat shrink into position.


Dave,

When you do this, are you talking about welding on the backside, or just using an oxy-acet torch with a rosebud to heat it?

I'm watching that video now, reminds me of the old South Bend videos on How To Run A Lathe. Could be the same announcer...LOL

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Re: Cupping, oil canning, potatoe chipping

Postby tungstendipper » Wed Jan 31, 2018 4:24 pm

Dave,
Great movie! I'm expecting a coloring book to come out with Mr Shrink to color. Boy! That would give you something to do on those cold Minnesota nights! That was so good, even I go it!
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Re: Cupping, oil canning, potatoe chipping

Postby MinnesotaDave » Wed Jan 31, 2018 11:47 pm

aland wrote:
MinnesotaDave wrote:Another is to heat the opposite side after welding and let it heat shrink into position.


Dave,

When you do this, are you talking about welding on the backside, or just using an oxy-acet torch with a rosebud to heat it?

I'm watching that video now, reminds me of the old South Bend videos on How To Run A Lathe. Could be the same announcer...LOL

Alan


Rosebud or cutting torch for heat. It has to make a line of red to work - like in the video.
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Re: Cupping, oil canning, potatoe chipping

Postby MinnesotaDave » Wed Jan 31, 2018 11:48 pm

tungstendipper wrote:Dave,
Great movie! I'm expecting a coloring book to come out with Mr Shrink to color. Boy! That would give you something to do on those cold Minnesota nights! That was so good, even I go it!


I show it in class - high school kids and us adults learn from that old video :)

If I ever see a new fangled version of it, it'll have to be really good before I use it instead :D
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