Thread: Workshop Compressor

I'm wonder what you guys would recommend I look for in a workshop compressor, just in case that auction or garage sale etc turns one up on the cheap I have an idea if it will be suitable.

First two uses I can think of would be running air lines around the shed to clean down machines, second would be to use with a small benchtop sand blasting cabinet I have.

I guess spray painting would also be a possibility. What other workshop, woodworking, metalworking do you guys find it useful for and what specs, features should I look for in a compressor.

Also I guess what issues in a second hand compressor are easy to spot and avoid?

Interesting question. I'll expect lots of opinons once peps get reading it!

I admit I only use second hand air compressors, however treat them with respect.
see the thread: 'Stay away from those old compressors' on the 'iforgeiron' forum.

Without knowing exact procedures, my greatest concern is for how rusty the inside of the air tank is. (thus the scary stories in the above thread).
Then knowing the reliability of the pressure cut off- does it work? and is it not too high a pressure for the tank (too high = bomb).

For actual capacities- always the-bigger-the-better! Grit blasting cabinets and many rotary air tools gobble big cubes of air, so the Cubic Feet per Minute (pumped by the compressor) needs to be generous.
Example; my dad has a 40 year old Clisby, 6 c.f.m. runs fine. I have a Hafco SB-100 cabinet (the smallest!) and it kills that compressor.

Shall be interesting to see the other responses.

AndrewOC

Jeez there are some scary stories in that thread and some links to some horrific photos.

Is there a Australian Standard for new compressors?

The only one I really have had much experience with was the one my Grandfather used when i was a kid which was a V-Twin. Dunno what happened to it.

It just like dust extraction - if its not 3hp at least you are just kidding yourself it works

Cheers

Doug

Originally Posted by DSEL74

I'm wonder what you guys would recommend I look for in a workshop compressor, just in case that auction or garage sale etc turns one up on the cheap I have an idea if it will be suitable.

Funny you should ask, I just came inside after a friend & I got my Hydrovane compressor working again.

Anyway, it's totally dependent on what you want to do. Some tools suck air like you wouldn't believe, others not so much.

I have 'successfully' spray painted with a nominal 8 cfm unit. It won't run a die grinder.

For decent volume blasting using garnet and a 6mm nozzle, I use my Hydrovane compressor. That is 120 cfm free air delivery. You are not going to run it in any place without 3 phase power as it has a 25HP 3 phase motor driving it. Really it's too big for a lot of stuff I do and arguably too small for serious blasting. I've recently picked up a biggish V4 compressor head that I should be able to slow down to 30 cfm and run off of a 7.5HP motor.

I wouldn't consider anything under 20 cfm but - I'm impatient and run a blast cabinet that uses a lot of air. Think a minimum of a 15A 240V power dedicated supply if you don't have 3 phase. If the unit will run off of a normal 10A GPO plug, it's too small.....

PDW

As other have already said big as possible... I have a 3hp compressor which I think is around 15 cfm which is good for most air tools and painting but doesn't even come close to being usable for my sand blast cabinet. For that I think I'm thinking of converting an old holden red 6 into a compressor pump and running it off the PTO of my tractor.

Well I am building a nuclear power station under the tank-stand at the back of the shed so that I can run my dust extractor and compressor!

Originally Posted by gallegos

As other have already said big as possible... I have a 3hp compressor which I think is around 15 cfm which is good for most air tools and painting but doesn't even come close to being usable for my sand blast cabinet.

If all the planets are aligned and the red dog crosses the road at midnight, a well made and well run in 3HP compressor can at most push is 12 CFM. Typical max values are in the 8-10 range with occasional higher quality units getting to 11 cfm.

95% of what I do with my 2.5 HP cheapie is clean chainsaws and clear clogged taps and dies. Occasional I blow down other machines and have done a little bit of spray painting. I've been waiting for many years for the stupid thing to die but it seems to keep running.

I'll have 2phase in the new shed already and will need 3phase to run the lathe. 5HP 3phase or bigger is that the way to go then? Or can you get too big for blowing down machines etc

I've got a 7.5 cfm compressor. It's a Binks Bullows with a Swedish pump.

Unless you have a very large tank, it will struggle with a medium sized die grinder.

You can easily spray paint using low pressure guns at 35 psi - I also have a Binks Bullows spray buddy which can easily do this.

But for jack of all trades, a compressor should be as big as you can run off of your power supply.

On single phase 240 I would be looking at getting 12 cfm.

Rob

Originally Posted by DSEL74

I'll have 2phase in the new shed already and will need 3phase to run the lathe. 5HP 3phase or bigger is that the way to go then? Or can you get too big for blowing down machines etc

A large compressor is not needed to clean down machines. There are some folks around that will tell you that you should not blow down machines at all with a compressors as this forces swarf and crap into the wrong places and to a large extent I agree with them. The only time I put a finer nozzle hard up against stuff for cleaning is on chainsaw chains and bars and things like taps and dies otherwise when I blow down machines I tend to use a medium size nozzle air gun and hold the nozzle back from the machine.

I have a newish single phase 16cfm and it will not keep up with a die grinder or small hand held grit blaster.

I have a 10hp Kubota diesel engine doing nothing and I am looking at fitting it up to a 35cfm compressor head. And for some jobs it will probably struggle to keep up.

Could be a noisy problem (for the neighbours) if I move into a built up area though.

Ken

Originally Posted by Toggy

I have a newish single phase 16cfm . . . .

Is that really what it is or just what the manufacturer says it is? How many HP is the moptor?

To generate 16 CFM with single phase it will need to be a 5HP motor which will require a dedicated 20A single phase circuit.

Originally Posted by BobL

Is that really what it is or just what the manufacturer says it is? How many HP is the moptor?

CFM by itself is pretty meaningless...... or at the very least a figure than can be "massaged"(and it certainly has been). Even the motor "hp" can be massaged.

To steal a line for a site a came across "I have a 600 CFM compressor in my garage that uses only 1/3 HP! (It's a fan delivering 0.1 psi.)"

Evaluating True Horsepower and CFM Ratings of Air Compressors

I bought a 12 or 14cfm I&R compressor must be getting on to 30 years ago. Went shopping with a mate a couple of years back when he was looking for a compressor, the numbers that were being quote were huge, one of the salesman even said they were rubbish but he had to put the same rubbish on his labels and the others or he wouldnt sell any.

I have got by with a 12 cfm inline twin cylinder comp for years, I have to wait for it to catch up sometimes when
using the 3/4 impact gun or a die grinder but it handles the air gun and spray painting no probs, it 2 hp and runs
off a 10 amp supply, (through a cheeeep 10 amp powerboard at the mo).

Years ago I bought a 12 cfm direct drive compressor, BIG MISTAKE, start up current is to high, it needed to be plugged
into a 15 amp power point and if you wanted to run it on a decent extension lead you would have to dump the air outta it to get to start.

I also have a 20 cfm Hydrovane comp, it needs to be wired up but so far never needed it.