Quote: Just a quick note. I sandblasted the heck out of most of the parts shown in my posts. The trick to not warping the part is to slow down the air speed. I did alot of experimenting with sand blasting due to the huge amount of posts claiming total destruction of panels from heat. It is not the heat! The speed at which the sand hits the metal has to be slowed to a point that ti does not "peen" it. Sand being thrown at metal at a high rate of speed has the same effect as a whole bunch of little dudes beating on the panel with little dude hammers! I saw first hand what happens with high velocity sand blasting on metal. It warps from the "hammer effect" not heat.Food for thought.
Good observation and totally correct. Sandblasting effectively peens the surface just like shot peening causing compressive stresses and that can cause bending and warping. The amount of bending is a function of the media type, blast pressure, impingement angle, and time. Specially made little pieces of metal called "Almen Strips" are used during commercial shot peening and abrasive blasting procedures as part of the process and quality control. You blast the Almen Strip just as you would the part your going to be working on and measure the amount of bending to verify the process is working correctly. The strip will bend in an arch up toward the surface that has been blasted.
We make jet engine parts where I work. Sometimes we do abrasive blasting to prepare the surface for dry film lube coating and we do this test every time. Incidently, if you flip the blasted strip over and blast the reverse side exactly the same, it will straighten back out. However, that's not likely to fix a warped body panel.
