Sand Blast Box air pressure

Steve Plucker

Steve Plucker

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I have a Harbor F. blast box. What should the air pressure be at the Air Compressor and the regulator before the air gets to the gun?

Thanks.

Pluck
 
Can't help you but I had a blast box from HF and my compressor would produce about 100 psi continuously through the hose and that wasn't enough to make it operate satisfactorily. Seems to take quite a bit of air at a pretty fair pressure or you get to work only in bursts then let it build up again. My compressor disintegrated and I never replaced it. Gave the tank away as well as the blast box. It looked to have been made from a 55 gal. oil drum. The compressor was sitting on top of an upright tank and vibration cracked the pot metal it was made out of, then it became lethal and I shut it down to watch its dying throws. The tank was later used to make a wheel barrow. The box is working well with a 220V three horse compressor, I am told. Don't know the specks. If I find out I'll send them. Works well with glass beads he said.
 
A lot has to do with the size and condition of the tip you are using in regards to what size media your are using. Keeping the media clean and having a cyclone or vacuum hooked up along with moisture traps helps. Then also size of tank. We have a 60 gal tank and I run at about 60-70 pounds pressure, tank shut off set at 150. We have a decent compressor running 220, it handles what we do in the shop, but still that tank get depleted quickly a there is a lot of air going thru the tip when in use.
Re the HF box, we have the same one. It is sold under many different names. first thing I would suggest is on the view port, install threaded pop rivet inserts so you can change the plastic glass protector from the outside, then install real lights. You will find in use, the plastic protectors fogs up real fast from media hitting it and is a royal pain to reach inside to hold the nuts for the screws holding the frame on. I hope this year we can install better lighting in ours, I am thinking LED. (along with maybe new tips, ours are plum wore out)
 
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I regulate the pressure to 45 lbs, cuts good and it doesn't make the media into dust as fast, I keep the big pressure pot sandblaster to that pressure too--- air lasts longer, media lasts longer, nozzles last longer, sand hose lasts longer, harder to damage to items being cleaned
 
There's no such thing as a an air compressor that's too big. Only ones that are too small. The garden variety air compressors that are rated at 15 to 20 CFM, (cubic feet per minute) at 90# pressure won't keep up to a 1/8" sand blasting nozzle. They are adequate for air tools, but sand blasting requires a huge air supply. I would look for an older unit, still in good condition, that runs with a 5 or even 7 HP electric motor and 120 gallon tank. The bigger the better. I run a very old 2 cylinder compressor that was salvaged from a factory that once was powered by a 20 HP electric motor. It's probably older than I am. I rigged it up to run with a farm tractor PTO (power take off). It's been reliable for 30 years and puts out about 60 CFM. It will hold 90# pressure with a 3/16" nozzle. So, the compressor that you need to run a cabinet needs to be 30 CFM or larger. Hope this helps.
 
I have a HF cabinet and run it with an average output of probably less than 15 cfm . Had problems with HF gun and replaced it with a better one. Works for me . I seem to blast in spurts not long trigger times . If you have a lot of blasting and in a hurry then as Mike says go big for cfm .
 
I regulate my pressure at 80 psi.

A TP tools gun and pick-up tube will make the HF box a better tool and use the air you have available more efficiently.
 
A word of caution about a large, 2 stage 7.5hp compressor. I thought bigger is better, sold a 5hp, 60 gal 2 stage and bought a 7.5hp, 80 gal. Man i have enough air to power everything in my one man hobby shop. Problem is with a big compressor is that it must run for extended period of time and get hot to keep the oil from becoming contaminated with water. A lot of my use was to air up tires, drive a few nails, etc. whereby the compressor will start but not get hot, hence a water in oil problem. My solution was to return to using my old small compressor for the more moderate shop use and only run the large one when using air tools. Something to consider before investing in a high hp machine.
 
As Kurt suggested above, back your pressure down. At that pressure, the media tends to shatter when hitting the object you are blasting.

Also look at using carbide tips and aluminum oxide media.
 
redmodelt said:
A lot has to do with the size and condition of the tip you are using in regards to what size media your are using. Keeping the media clean and having a cyclone or vacuum hooked up along with moisture traps helps. Then also size of tank. We have a 60 gal tank and I run at about 60-70 pounds pressure, tank shut off set at 150. We have a decent compressor running 220, it handles what we do in the shop, but still that tank get depleted quickly a there is a lot of air going thru the tip when in use.
Re the HF box, we have the same one. It is sold under many different names. first thing I would suggest is on the view port, install threaded pop rivet inserts so you can change the plastic glass protector from the outside, then install real lights. You will find in use, the plastic protectors fogs up real fast from media hitting it and is a royal pain to reach inside to hold the nuts for the screws holding the frame on. I hope this year we can install better lighting in ours, I am thinking LED. (along with maybe new tips, ours are plum wore out)
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I did the same on my Harbor Freight cabinet. I also caulked all of the joints and seams prior to firing it up for the first time.
 
I like lower pressure and lots of volume, at least 25 or 30 cfm.If you can't get the cfm you need, you can buy smaller tips. I use the ceramic tips, work well and are cheap and easy to replace. However, they only last for less than an hour and then time to replace. Only cost 2 bucks so no big deal. I run about 45 lbs when blasting. If I come to a stubborn spot, I can always up the pressure a bit, then drop again. Remember, if sandblasting sheet metal keep your pressure low, keep your tip at an angle to the surface, and keep moving. Otherwise it can warp the surface.
 
1crosscut said:
I did the same on my Harbor Freight cabinet. I also caulked all of the joints and seams prior to firing it up for the first time.
Click to expand...

In addition to the above, I keep a 3inch wide paint brush in the cabinet to dust off the inside plastic sheet. Really enhances the clarity of the window. I updated the suction tube to one made by TP tools specifically to improve the media flow in HF cabinets. As to pressure and flow, the more the better. My priority is fast results, as my volume of work is not that high, so media cost is not a priority for me. I use a 5HP 80 gal setup. Plenty of volume for anything.

Changing the window hardware so it's easily changed from outside is crucial.
 
P.S. Remember to strip the paint off any parts first. As Peter said CFM is what it's about. I've seen big compressors that have small CFM. 20 - 25 CFM is good.
 
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