Oil Canning Roof

dhutton01 said:
I read this on another forum. Never read this before…

“Press formed sheet metal has surface tension. Sanding to bare metal can and will allow that steel to relax. Thus beer canning.”

Don
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I can't see how surface tension would be compromised or changed by sanding with 80 grit on a dual action sander. Does 80 grit really remove material or just scratch it up? My opinion would change if say 36 git or coarser was used to sand with, I believe that grit would remove material that could change the tension properties in the metal.
 
MJM said:
I can't see how surface tension would be compromised or changed by sanding with 80 grit on a dual action sander. Does 80 grit really remove material or just scratch it up? My opinion would change if say 36 git or coarser was used to sand with, I believe that grit would remove material that could change the tension properties in the metal.
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I believe he ment to say relieves stresses. Working metal can induce stresses-anything from stamping to machining. Bringing up the metal to a certain temperature can relieve these stresses. Many times this is done intentionally. I would have a tough time believing this could be done with sandpaper, but sheetmetal is a fickle thing.
 
UAmember said:
I believe he ment to say relieves stresses. Working metal can induce stresses-anything from stamping to machining. Bringing up the metal to a certain temperature can relieve these stresses. Many times this is done intentionally. I would have a tough time believing this could be done with sandpaper, but sheetmetal is a fickle thing.
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You bring to the table valid points, especially the comment about temperature and it's effect. So if 80 grit scratches aren't an issue with regards to reliving stress, I wonder if the dual action sander actually reliefs stress to some degree. The sander vibrates, so that is tiny minuscule hammer hits.
 
MJM said:
I can't see how surface tension would be compromised or changed by sanding with 80 grit on a dual action sander. Does 80 grit really remove material or just scratch it up? My opinion would change if say 36 git or coarser was used to sand with, I believe that grit would remove material that could change the tension properties in the metal.
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Maybe our resident engineering expert will weigh in. I honestly have no idea. Just posted it for interest and discussion….
 
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