Problem with abrasive blasting - Aluminum Oxide

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Old 09-25-16, 08:48 AM
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Problem with abrasive blasting - Aluminum Oxide

I have a 48 year old classic car that I decided to give its second major restoration to myself.

So I set about getting tooled up to shot blast, starting with a replacement hood as my test piece. After a trial with glass media which seemed slow with a hand held gun/canister I settled on Aluminum oxide media, and upgraded to a 20 lb. Pressurized Abrasive Blaster (Harbor Frt) fed from my 21 gal/125 PSI Compressor running at 90psi with oil/water filters inline.

Some initial tests with small amounts of shot looked good, with the old paint and rust coming off well from the steel hood with a fine mist of shot and air pressure.

The problem - with everything set up per the manual, is that when I open up the trigger, fully, with the tank fully charged now, the abrasive dumps out in one rather slow steady stream that looks like it is 50% shot, 50% air, and 40 seconds later the tank is almost empty. Using the throttle valve doesn't seem to help.

Am I missing something ?
 
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Old 09-25-16, 09:56 AM
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It's just my opinion, but I would not media blast sheet metal to remove paint. Maybe in crevices or folds, but on flat metal, a rotating media such as a lap sander would work better. Yes, you will use up a good bit of media with all the valves open fully, as described in the instructions.
 
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Old 09-25-16, 10:50 AM
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I agree, flat metal is better sanded or even chemically stripped. If you aren't careful you can warp large flat pieces of metal sandblasting although I doubt your blaster has that much power. Sandblasters probably require more cfm than any other tool so that might also be part of your problem.
 
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Old 09-25-16, 11:36 AM
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fed from my 21 gal/125 PSI Compressor running at 90psi
That definitely won't cut it. It will work for short blasts but it needs to be allowed to build up pressure. Most compressors of that type can only produce around 4 CFM at 90psi.

Your blaster needs 6-25CFM of air.
 
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Old 09-25-16, 11:54 AM
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Gosh, I skimmed right over the air capacity of the compressor. Definitely not enough CFM. Stand up 60 gallon would work better.
 
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Old 09-25-16, 06:18 PM
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Excellent, thanks. Obviously I missed the cf of the output and cf for the blaster. I do have a glimmer of hope in that the 40psi rating of the compressor is around the bottom end of the blaster's range but I know that 90psi is a non-starter.
 
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