sizing an air compressor for blasting

[wtb853]

I have been toying with the idea of purchasing a blasting cabinet setup. Many of them show an air requirement around 9 cfm @ 90psi. That translates into a large and expensive compressor. I would only be using it for small parts here and there. Besides sandblasting the compressor might only see bike tires and a brad nailer. I am curious if I could get by with a smaller compressor and a little patience.

What size compressor do you all use for your blasting setups and will a smaller compressor keep up if you are patient?
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1951 M38 (MC25486)

[wilfreeman]

My compressor is 5hp/13cfm/220v/80 gal. It runs my blast cabinet pretty well, but doesn't like running a siphon type blast gun like you use for larger parts outside the shop.Using a small compressor can be done by sizing the tip correctly though I would recommend at least a 5hp/15cfm/220v/60gal for any level of enjoyment of doing it yourself. I know you said you could do it with some patience, but you'll soon get tired of waiting - trust me, I've been there, and am at the same point now with the larger parts - would rather pay someone than struggle with too small of a compressor for the siphon blaster.
In the end, it's your choice - that is just my 2¢ worth.

Matt

[major519]

For blasting, bigger is better!
I have seen this question posted often and have been there myself. Save your pennies and get a decent machine with high cfm.
Conversely, many guys opt to purchase a "deal" at one of the home improvement stores. Sure, they look nice, all new and shiney but why not hold out for an industrial type at an auction sale or swap meet?
A friend of mine was able to purchase a gas driven 120cfm air compressor from a construction auction for $500. If you have the room and noise and dust is not an issue, buy a portable type. You can park it behind the shop and regulate it down for your sandblast cabinet or use it with a full size pot setup outside for larger stuff. Thats my plan!

[OKCM38CDN]

I have been using a Harbor Freight 21 gallon 1 1/2 HP compressor for years... I originally bought it for painting and such... I could run a blast cabinet using sand but I had to be very patient... max pressure would be about 40 psi after the original burst... and forget using glass bead, not enough pressure.

I was looking to upgrade to a 60 gallon and found a deal on the Campbell Hausfeld website... I found a 60 gallon 3 1/2 hp unit for $420 plus shipping... This is a factory reconditioned unit and has a 1 year warranty... (http://www.chpower.com/category/air-compressor-hot-buys_28100)(I am sure if you check other manufacurers you might find the same deals)

I purchased it and had it shipped to my work, saved me $50 (Work has a loading dock and no lift required it came freight not by UPS)... I got it up and running over the weekend and am now able to blast with glass bead at 120 psi and the parts come out clean...

From someone that has been there; done that; and have the "T" shirt... Save your money and invest in a large compesssor... well worth the expense... wish now I had done it that way years ago...

[donthedickens]

wtb853,

You can sandblast with a small compressor doing the blast a few seconds, wait for it to build up and blast again. You'll get a few more seconds out of the process if you start blasting just before the compressor cuts off at top pressure setting. You're then blasting at top range and the compressor is still working to keep up instead of starting when you have run the pressure down. You WILL tire of this very soon.

I had a small compressor when I started in the WWOB (wonderful world of blasting). I got a second small compressor (because it was free). I made a quick connect tee fitting for the air lines and set the pressure on both compressors about the same. When I want to blast I set up the fitting, an air line from each compressor to the tee and one from the tee to the blaster. I can run what I need.

Set up a air line dryer. Moisture will clump the sand in the nozzle.
_________________
Don Norris
Southeast, NC
53 CJ3B F134
59 Willys Pick-up truck
54 CJ3B is my M606 wanta-be in progress (rough)
M100 trailer

[wilfreeman]

Yes, yes - I forgot about the dual small compressor setup. When my brother first set up his body shop he didn't have the funds for a nice compressor, so he did the same thing with a 5hp/60 gal and a2 1/2hp/20gal - worked fine. As a matter of fact, I still have that old 2 1/2hp compressor in the corner of my shop covered with 'a1 parts - thanks for reminding me about that setup! I'll have to try that in the spring.

Maybe that idea is more feasible for you too wtb853?

Matt

[wesk]

It works to a certain degree. What you are really doing is using more air storage space but the two compressors if not equal in performance will allow the stronger guy to overpower the weaker guy so you are not combining the output of two compressor pumps. You are only combining the air storage capacity of the two. Also you should use the two 1/4" hoses to feed the "T" but then use a 3/8" or 1/2" hose to feed the sand blaster from the "T".

You can get the same result by buying a dead old industrial compressor with the huge 60 or 80 gallon tank and piggy backing your 5 HP compressor to the big tank with a "T" setup.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

[major519]

Remember, CFM (cubic feet per minute) and PSI (pounds per square inch)are the key ingredients.
I see everyone talking HP (horsepower) here. That is just simply how much power the electric motor has to turn the compressor. A compressor will only output as much cfm as it is rated for; period.
A compressor motor running full tilt consumes a lot of electricity, especially when it has to ramp up constantly on and off to keep up.
A higher CFM compressor with a higher HP motor and an equally sized tank is what is required. It is all a formula...
240v is also required. Higher voltage equals less amperage draw.
A 5hp 15cfm compressor will hardly ever do the trick; my club has one and even continuous use of an air grinder or chisel is a pain in the a**.

[wtb853]

Thanks for the quick responses. I get the message and will save accordingly.
_________________
1951 M38 (MC25486)

[wesk]

[BullRun]

One other factor to consider is noise.

Running a compressor all day in a room will drive you nuts from the noise. If you can swing it get a rotary screw compressor and save your hearing and avoid the headaches. Or isolate your compressor and run a long hose.