Bead blasting help, please!

A. Brett Schaller

A. Brett Schaller

Joined
Mar 22, 2001
Messages
787
Help! I'm trying my hand at bead blasting, but things are not going well. So far, I have not even been able to take the shine off Micarta by blasting. It seems that I'm not getting enough velocity behind the abrasive.

I got one of the Harbor Freight two door cabinets, a compressor, and 80 grit glass beads. The cabinet specifies 5 cfm at 100 psi, while my compressor (10 gallon) is only 4cfm at 90 psi, so I realize it's a bit small. I didn't think that would be much of a problem, as I've read in previous threads about guys doing small blasting jobs with the small pancake compressors, and I'm only thinking of doing one blade and a pair of liners at a time.

I thought the problem might be the small self-coiling air line, so I picked up a larger line from Harbor Freight. Thinking it might also be the gun the cabinet came with, I also picked up one of their cheap gravity feed hopper guns - I saw Peter Atwood use one of these to good effect in his video. Still no good.

I SEEM to be getting good pressure out of the compressor when it's not hooked up to the blast unit, but that's subjective - I've never owned a compressor before. Is there a way to test the PSI, maybe?

I've checked for air leaks between the compressor and the blast unit. There are none.

Any advice you could give me would be greatly appreciated.

Thanks!
 
Couple of things.
1) Put a pressure gague on the tank,so you know what the pressure is.
2) Adjust the regulator for a higher pressure if it is low.
3) Many (most) of the cheaper compressors and motors are rated higher than they actually produce.(Think of your shop-vac and its 3HP motor?) It may say 4CFM/90PSI but it probably produces 3CFM/70PSI continuous.
4) Make sure you got the right kind of beads for the gun you are using.
 
I just started blasting myself and found that the 80 grit glass beads would hardly knock the shine off my ATS-34at RC60. I mixed 70 grit aluminum oxide with the glass bead and I really like the finish I got and I am using the smallest orifice that came with the HF cabinet setup. I have a 5 hp Blackmax air compressor and I shoot it at 90-100 psi. Hope this helps! Caution...blast a test coupon because it could be too aggressive for your tastes.
Jim
 
Well, I bought a pressure gage today. My compresser was already equipped with one, but I wanted to test the accuracy. Result: The pressure seems fine.

My compressor is only 1.5 hp. I'm not sure what difference the hp makes, as long as I'm at the pressure I want (I was running 90 - 100 as well.) Fillling the tank faster?

I suppose I could try some aluminum oxide, but you'd think that 80 grit glass beads would at least knock the shine off Micarta! It still seems I'm doing something wrong; I'm just not sure what.

My gun came with three nozzles, but they're all the same size. I guess I'll check HF to see if they sell smaller sizes.
 
I've got a wally world special air compressor and harbor frieght blast cabnet. I'm using 80 grit beads.

One thing I've noticed is that I have to make sure the beads are falling back into the sump while blasting and I can only go for two or three minits before having to let the compressor recharge. I think I'm running 100 psi, can't remeber. Are you getting beads to come out the gun? If so you may be running down the pressure after the first minit and don't have enough veloticy. Before I got the beads I used play sand to good effect, but it was a little course for my taste.
 
I have a Harbor Freight bead blast cabinet also. I use a pretty good size compressor but I've used a small one before that (the same one I use for my nail guns) and it worked fine you just had to allow it to catch up if you were doing something much bigger than a pocket clip.

I would suggest making sure you don't have any kinks in the lines, that all are open and working as they should as well as checking the set up of the handpiece and nozzle to be sure its all put together correctly. Then if all that checks out I'd suggest making sure the suction part of hose set up that siphons the glass beads into the nozzle is submerged in the beads nice and deep and that you are not letting it expose so it is just sucking in mostly air and very little of the beads. I have to stop after bigger jobs to shove all the beads back over top the siphon so it buried again if I want to maximize the use of the beads and my time.

You might also make sure you stuck the proper amount of beads in the cabinet. Mine called for 10 lbs and I've found it works a little better with 12 to 15 actually.

Of course the other big killer of the system is moisture. If you haven't drained the compressor lately take out the plug and do so. If you get a good bit of water coming out you may have found your problem.

STR
 
Step down in nozzle size(like from 3/8" to 1/4" and get a ceramic nozzle, if they offer one, they last a lot longer than steel. That will give you some added velocity.
Another thing is to get some 150 aluminum oxide blast media from your local abrasives supplier. Mix it 50/50 with the glass beads. I'd be willing to bet you have no more troubles then.

You can vary the AO mixture heavier, or lighter(like 70/30AO/GB, etc.) to suit your needs.
I pre mix it in 1 gallon milk jugs(in several combinations) which hold about 10 pounds of mixture, which is about what one of those cabinets takes.

Good luck.

Like Stacy said, compressor people lie about horsepower ratings on those things, big time. I have a 3.5HP Quincy that runs on 120V. :eek:
Yeah, it could happen.:rolleyes:;):D
 
Yeah, I would recommend some aluminum oxide media with the glassbeads.

Or blast it first with filtered sand (use a fine sieve like the one in the kitchen :p ), then blast it again with the glass beads.
 
STR touched on the moisture problem. That will cause the beads to accumulate before exiting the orifice and completly stop most of the abrasive from doing the job.I had that problem and added a water trap which fixed the problem completely.You can tell if you have the same problem by doing a little blasting and then taking the nozzle off and looking to see if you have a mass of abrasive stuck together in the end.If so clean it out and try a test blast ( just a short one ) to see if that makes a difference,check the orifice again for the mass of abrasive starting to form again.If it is , get a trap . It doesn't take long at all for it to clog up if you have a moisture problem.
 
Thanks to everyone for the advice. I'm relieved to see that my compresser should be up to at least small jobs - it's the biggest compresser I can fit in my shop at the moment.

Moisture doesn't seem to be a problem at the moment, but one of those in line traps sounds like a good idea anyway. It looks like my best bet is to try a smaller nozzle and some aluminum oxide mixed with the beads.

By the way, my compresser's owner's manual says to completely drain the tank every night. Is this really necessary, or can you leave it a couple of days?
 
A. Brett Schaller said:
T............................

Moisture doesn't seem to be a problem at the moment, but one of those in line traps sounds like a good idea anyway. It looks like my best bet is to try a smaller nozzle and some aluminum oxide mixed with the beads.

By the way, my compresser's owner's manual says to completely drain the tank every night. Is this really necessary, or can you leave it a couple of days?
Click to expand...


I live in about the same climatic conditions you do and I rarely drain mine. I've not ever had a moisture problem, except during the monsoon season in summer when it gets hot and humid here. I drain it after using then, or every night, as there just so much moisture in the air.

You can see the moisture blow out of the tank then, but at no other, drier part of the year does that happen.
It's also a good idea to drain them occasionally and run the compressor with the petcock open to dry the tank out in case condensation has built up in there. Then just shut it down and leave the valve open so it can continue to dry till the next time needed.
 
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