Air compressor min CFM for media blasting

[tdskip]

Sorry guys, I know I asked this question in the last 24 months but I can't seem to find it via searching.

To be able to effectively, without watching the grass grow, media blast parts what CFM spec air compressor do I need to track down?

 

[TR3driver]

First, pick the blaster you want to use. Ratings range from 4 cfm to 17 or more.

Then multiply by 7 (90 psi ~= 7 atmospheres) and divide by the size of your pocketbook.

I'm happy with my 4 cfm blast cabinet (although I wish the cabinet were bigger) and 17 cfm, 80 gallon compressor. With the tank pumped to 170 psi, it will run the blast gun for longer than I care to stand there.

But the old, 7 cfm, 20 gallon, 120 psi single stage compressor was the pits. By the time I got started good, the compressor was "out of breath" and I had to wait for it to catch up again.

 

[Tinkerman]

TD are you using a blast cabinet or an pressurized sand blaster? I have a 240 volt, 5HP 60 gal single stage compressor. It is a Craftsman oil-free that puts out 14 cfm @ 40 psi and 9.9 cfm at 90 psi. It operates my bead blast cabinet quite well but was marginal on the pressure sand blasting because of the low cfm. It kind of depends on what you are going to do. For small parts in a bead blaster it works great. You just have to watch your air flow and give it a rest every once in awhile to let it catch up. if your going to paint with it and do large pieces you really need to get a two stage compressor. They are more expensive but have come down quite a bit in the last ten years. You might also consider a two tank system.
Take a look on line at Harbor Freight or Northern tools and see what they have to offer.
BTW I like the oil-free but it sure is noisy.

Good luck, Tinkerman

 

[tdskip]

Thanks guys. I have this cabinet;

which calls for 10 CFM @ 100 PSI and having been running it off a unit like this;

Not my compressor so I don't have all the specifications, and it recently starting losing it's ability to generate pressure so it's a bit academic at this point any. LOL.

I would like to be able to blast everything from carb parts to suspension parts. Despite the tank being underrated it actually worked OK in short bursts before fading, but I'd like to be able to just crank the parts out.

Is there a specific siphon gun you guys would recommend?

Thanks!

 

[Tinkerman]

TD, I wouldn't recommend any type of siphon gun. If your talking about big stuff to sand blast outside, you need to use an 80lb or larger pressure blaster. Again HF or Northern would have what you need and they usually come with a gun. My comments stem from trying to use a siphon gun on some fenders back in the late 80's. It was, to me, mostly useless.
The problem with the compressor that you are using has at best a 10 to 20 gallon tank. You need more like a 60 to 90 gallon tanks then you have some staying power. I mentioned using two tank. If you had two 60's hooked up in line it would give you double the capacity and more time in the blast booth. In the pics you can see what I have. I'm with Randall would have liked to have had a bigger cabinet, but what I got is what I use. I have been using this rig for about 12 years now and it continues to do the job. There are two pictures.

Tinkerman

 

[martx-5]

Just some information...At work I've found out that our blast cabinets work just fine at 70-75 psi. I've got a chart at work that shows how much cfm you need for each nozzle size with whatever pressure you want to run it at. We have one glass beader with four #5 nozzles in it that requires 50 HP to operate. I lowered the pressure and can now get away with a 35 HP compressor. Try lowering the regulator pressure, and you'll use less air, and the guns should still blast just fine. Worn out nozzles will also suck up more air then necessary, so keep up on the maintenance of the guns. Also, a rule of thumb, it takes about 1 HP of compressor for 3 cfm of air. Be careful, some of the horsepower ratings for compressors sold today are way too optimistic. Go by the cmf @ 90 psi.

 

[trfourtune]

I agree. You have to go by the rating of cfm and the pressure it is at. Also, you might want to look at the duty cycle. Some are very low 50% or less. If you want to be able to "go at it" without stopping, you should be looking for 100% duty cycle or at least 75% or more. With an external blaster (non cabinet) of 100lb capacity, you nead at least 20cfm at 120psi IMHO.
Rob

 

[Hap Waldrop]

When I first open my shop 10 years ago, I just brought the air compressor I had in my home garage to the shop with the intention it would get repalced with a bigger two stage 240 volt unit or even a 3 phase unit, but 10 years later I'm still blasting with the same compressor and it does the job for me, which is on a professional level, meaning bead blasting everyday. I've got the big 3 foot Skatblast cabinet and the air compressor is a 110 6hp 6.6 CFM Husky unit, bought when on sale at Home Depot, cast iron motor. Quite hoinestly it does the job, when you compare to my buddy's set up, same blast cabinet 10hp two stage air compressor, I say his work time before you need to give the compressor a rest is 7-8 minutes, my work time before I need to give the compressor a brealk is maybe 5 minute, so not alot of difference for about $700 in the differenc in the cost of the compressors. Here's the deal almost any compressor you put in your home garage will exhaust your air compressor in 5-8 minutes of blasting time, and as you get into blasting, you'll quickly relaize that about as long at one time as you want to blast anyway. People I think look at a blasting cabinet before they get one as great thing, and they are great for this type of work, and very much needed, but blasting in cabinet is about as much fun as a kick in the privates , so 5 minutes at time is very acceptable work time.

I can't say enough good thing about a TIP Tools Skat Blast cabinet, the nozzles are way better than the HF/Northern variety, and the foot feed is a much better choice than the hand trigger, the light in the Skat Blast is normal flood light and it works alot better than the cheaper units lights. Here's the deal though if you have the HF type units and you would like to spruce it up a bit, you can got the TIP Tools website and buy upgrade for your cabinet, replacment gloves, dust vaccums, bettrer tips (I use the graphite ones, they are more expensive but outlast the regular ceramic ones 10 to 1) better nozzles, differnet types for media, I use fin glass I do alot of clean steel and carb bodies in my cabinet, but if you are stripping rust and paint you could go for aluminum oxide for example. Anyone who has or wants a blast cabinet needs to visit TIP Tools website.

 

[Tinkerman]

Hap, I couldn't agree more about TIP and their blast cabinets. The availability of parts is really important. I don't know about you but I go through gun tips fairly fast so being able to get replacements is important. My vacuum motor went out and I had a replacement within days. Mine is also the three foot wide model. Not only that but it's made in the USA!

Tinkerman

 

[racer_x]

Sorry guys, I know I asked this question in the last 24 months but I can't seem to find it via searching.

To be able to effectively, without watching the grass grow, media blast parts what CFM spec air compressor do I need to track down?

I believe you need at least a 10 CFM at 90psi to operate the smallest cabinet at Harbor freight.

To get 12CMF at 90 you need a pretty big compressor. I have that Craftsman 5 hp 25 gal oilless compressor and it couldn't keep up with Gregg's pressure sand blaster or a orbital sander.

If you already have a compressor it isn't a bad idea to couple it with another compressor, you can more more CFM without throwing your old one away.

 

[tdskip]

Just triple checking what you all think about spec for glass bead blasting;

240 volts, 60 Hz, 23.5 amps (start up), 12.5 amps (no load); 120 PSI max; Air delivery: 8.74 SCFM @ 40 PSI, 7.70 SCFM @ 70 PSI, 7.47 SCFM @ 90 PSI, 6.67 SCFM @ 115; 20 ft. stripped power cord ready for 220 volt plug connection;

 

[martx-5]

At the bottom of this link is a chart that shows nozzle sizes and the cfm requirements at various pressures. This chart is based on continuous use. Anything smaller, and you will have to stop and allow the compressor to catch up. Most likely, you will be using a #2 (1/8") nozzle. If you set the air regulator on the compressor to about 70 psi, you<span style="font-weight: bold"> might</span> get things to work OK with the volume of the tank. That compressor shows 7.7 cfm at 70 psi, and you would need 15 according to the chart, so you'll only be standing around half the time. :laugh:

 

[tdskip]

Thanks Art - looks like I need to up the compressor size and mortgage the house here. All I want to do, now, is glass bead blast some carbs.... Argh!

(oh sure, wheels and other parts will follow in like 2 seconds but still)

 

[Tinkerman]

Shucks TD, I had to sell my first born but in the long run it was well worth it. I'm 8 years into the frame off and still using the rig I bought. I operate my cabinet at 80 psi and still find that I occasionally have to stand around playing catch up. Mine is 9.9 cfm at 90 psi.

Good luck, Tinkerman

 

[TR3driver]

I had to sell my first born

Pays to look around for a used one, IMO. Took awhile, but I found a 17.4 cfm 2-stage Craftsman for $500 on Craigslist. Just watch that you don't get a 3-phase motor by mistake (or else plan on buying a phase converter as well).