I have to tell you guys, heat has nothing to do with it, it is "mechanical compression". I used to think it was heat as well, after blasting in the dark and seeing the sparks as the sand hit. Sparks equal heat, heat warps metal.
But after being told what really causes it, I checked for myself. Sure enough, I sandblasted some metal and felt it, it was actually cooler! Yep, the air blowing on it cools the metal!
Mechanical compression is where the sand particles are acting like tiny hammers putting microscopic dents in the metal. Each of these dents is stretching the metal just as hitting it with a hammer would. Put a zillion tiny dents stretching the metal you are going to have warpage.
I know it is possible to sand blast sheetmetal and not damage it. However, I have seen such HORRENDOUS damage caused by sandblasting I never recommend it.
We are not talking "Dang, I messed up and now I have more work" kinda damage. We are talking "HOLY %#@ I &*%#@ED IT ALL UP AND HAVE TO THROW IT AWAY" kinda damage.
If you do it, be VERY careful.
Brian
