The Stovebolt Site Forums The Shop Area Paint and Body Shop Sandblast warpage?

Hello everyone -

I have just sanded down the outside of my 55 rear fender and it looks great! I used a DA sander and a Norton flap disk. Now I am cleaning up the inside of the fender. Due to the curves I will not be able to use the same approach for the whole thing.

Does anyone think using a siphon sandblaster set at 100 psi will cause any warpage?

Aren't the professional sandblasters using huge psi numbers?

Ross

ah you'll be alright on the inners in the curves,pretty hard to warp a curve! hmmmm! these old trucks are really thick also,pretty hard to warp these girls unless your in the middle of a flat panel holding the blaster in one spot for too long ( five seconds or more) give or take! and it's not the psi that does the warping .It is the heat created from friction, sand meeting metal at a very high speed!well something like that!

The 100psi should not warp the fenders as the contour provides good support. The only problem I see is the 100PSI may not be enough. I would use a scrapper to remove the heavy stuff and then one of those fiber stripping disks on a drill for what is left. Unless you are trying to get a show car finish on the inside surface this should do the trick.

I sandblasted both bedsides of my truck using 175 psi, didn't have any warpage issues. The real trick is to keep moving, don't stay on one spot too long. That helps keep the heat from building up in one area.

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

1stproject, I had the entire body, fenders, doors, hood, frame of my 49 sub sandblasted locally at a very reasonable price. No warpage. If you go this route you need to find someone who has experience in doing this. I found after trying the stripper, DA sander and elbow grease method that it was taking forever. IMHO blasting is the way to go and it does a much better job. It worked for me. Weeds

Like I said, even the pros can DESTROY stuff. I had a guy do it, I know. He DESTROYED a 1928 Buick door for me. And this guy was an owner of a sand blast company that had did a lot of work for me in the past. I had never gave him something like this before but with everything in the past, pickup beds and tons of other stuff. But that door, holy crap it was JUNK when he got thru with it.

I'm sorry, unless I REALLY knew the guy could do it, there is no way I would hand something to someone to sand blast.

Now, "Media" blasting with walnut shells or plastic beads, that is a different story. It won't harm a thing.

This is just one of the treads I have seen on the subject.. http://www.chevelles.com/forums/showthread.php?t=95691

Brian

Hello everyone -

To start with, thanks for the feedback. After reading all of the posts, I see there are a lot of varying opinions.

I can not afford to buy all "new" parts, and I don't want to use my limited funds on a professional, so I guess I am going to do it and just keep the blaster moving. (I have heard and read a lot of stories about professional sandblasting companies destroying parts. Scary!)

Thanks again! I will post how it goes.

Ross

I stripped one fender inside & out with DA's, roloc's, wire brush, liquid stripper and anything else I could find. It was a pain. I took the other fender, a bed side and the bed steps to the local media blaster. They bake first, then glass & plastic bead (not sure of the order). The parts came back rust free, but were much more susceptible to surface rust than the part I did. I ended up have to clean them up just to get rid of surface rust before painting and that was less than a week. I can't see where anything has warped and would do that again, but I'll be ready to paint ASAP and take one part at a time.

Use fine grit sand. 100 psi will do it if you get to a spot you can't get clean quickly move on then scrape and touch up again. Sand blasting is easier than typing!

I would say check out your sanblast guy before taking parts to him , I did a little background check on the 2 local shops in my area an found 1 was terrible the other nothin but good words ....so I stopped in an talked to the owner , an I told him what i wanted done ...he said he done Lotts an when he told me he would not touch the underside of my hood but would blast the top side an explained to me how the reinforcement ribs under the hood when blasting around them is a very tricky process and he couldnt gaurantee against warping it, I knew I had someone with expierience....fenders doors & hood came out very nice !

For whatever it's worth, this entire truck was sandblasted by me, interior, exterior and frame. I had no problems. See pics!