Compressors and sand blasters (again)

[malcolm]

I've been reading through a few threads about compressors and sand blasters. I want to sand blast things like wheels and bits of car, but if it's only a small stretch then being able to do bits of chassis and body would be handy too.

I've got a cabinet already with an enormous syphon gun that's too big for my compressors. rtbcomp and others have suggested the 10 gallon pressurised sandblaster (now available on eBay in 20 gallon size)

For the compressor I've got an old 200L belt drive with only 1.5hp motor, and a nasty old 50L Airmaster with 1.5hp motor. Thinking about taking the plunge and picking up something decent like the shiremore compressor SB15/200 I've only got 240V.

What do you guys think about those as a combination? Also for a fixed compressor how would you go about the pipework for a workshop air supply?

 

[oddball90]

Malcom you are going the right way, get the biggest air tank that you can afford. In the old days sand blasters used the towable compressors that run jackhammers, cause it is the volume of air supplied that you need for sandblasting. Would look to see if you can get a petrol engined compressor as they tend to supply more volume of air than a 240volt compressor. Also the larger diameter pipe from the compressor to tool the better the tool will work.

 

[malcolm]

I thought about picking up a road tow compressor a while ago. Masses of cfm, and reasoned that I could always sell it again if I moved on. Then went around in circles a bit and didn't get anything. Couple of other used petrol/diesel ones on eBay though - that's a good thought.

 

[rtbcomp]

Malcom you are going the right way, get the biggest air tank that you can afford. In the old days sand blasters used the towable compressors that run jackhammers, cause it is the volume of air supplied that you need for sandblasting. Would look to see if you can get a petrol engined compressor as they tend to supply more volume of air than a 240volt compressor. Also the larger diameter pipe from the compressor to tool the better the tool will work.

No. Get the biggest pump you can afford. All the tank does is reduce the stop-starting of the compressor. Obviously bigger pumps need bigger tanks to maintain a sensible duty cycle, but a large tank per-se won't give more air.

My sandblaster causes the compressor to run all the time so the size of tank is irrelevant in my case, I should have spent the same money on more cfm and used a smaller tank.

As for piping I'm using 15mm and 22mm copper. You can get plastic with push-fit connectors. If you go down the plastic route get pipe designed for compressed air, water pipe will shatter if hit under pressure.

Certainly the diameter of the pipe makes a big difference to performance, I'd use 22mm at least if you have one compressor supplying several outlets or runs over a few metres.

I've noticed the 20 gall pot. I'm thinking of getting one for my blast room to reduce the number of times I need to refill it and demote my 10 gall tank to use with cabinet for bead blasting.

I prefer to fill the pot at natural breaks in the work rather than when it runs empty, this increases the time I actually spend blasting.

 

[oddball90]

Yes but the motor and pump is the biggest you can get on 240volt, the bigger the tank the more blasting you will be able to do before you have to stop to let the compressor catch up. The 20 gallon pot says it works on 5/25 cfm, bet it is closer to 25 cfm to work properly.
The only way forward for electric would be a hydrovane(screw type) compressor which can supply a large volume of air.

 

[rtbcomp]

Yes but the motor and pump is the biggest you can get on 240volt, the bigger the tank the more blasting you will be able to do before you have to stop to let the compressor catch up.

Yes, and the longer you will have to wait before you can start again.

The 20 gallon pot says it works on 5/25 cfm, bet it is closer to 25 cfm to work properly.
of air.

5/25 means it will require anything between 5 and 25 cfm depending on the pressure you set the regulator to, in turn the pressure you choose depends on the work and blast media.

I've used 90 psi at the compressor's full output (14cfm) to remove rust, filler and paint, yet I've removed topcoat and left the primer behind at about 20 psi. (Pressure at the receiver, less at the pot). If I need more than 90 psi I need a bigger (or additional) compressor, or as you say, keep stopping and starting.

 

[malcolm]

That's another thing I had on my mind. Noticed some cheapo 14cfm compressors for under £200. While they won't be the longest lasting in the world is there any reason why 2 of those connected at the outputs wouldn't supply more air than say a single 18cfm compressor?

Or better still maybe some possibilities for mixing and matching with that great big 200L job that's sitting around unused.

 

[rtbcomp]

That's another thing I had on my mind. Noticed some cheapo 14cfm compressors for under £200. While they won't be the longest lasting in the world is there any reason why 2 of those connected at the outputs wouldn't supply more air than say a single 18cfm compressor?

Or better still maybe some possibilities for mixing and matching with that great big 200L job that's sitting around unused.

No problem. If you can get by with 14cfm if one compressor fails you can still get some work done. 2 x 14 = 28 and if you only need 18 cfm you'll spread the work between the two units, hopefully improving reliability.

I'd set the pressure switches to (say) 100 and 105 psi so that the units don't switch at the same time to avoid large current surges.

The downside of using as much storage as you can is that if you drain the down at the end of the day you waste more air, ie money.

 

[malcolm]

I can see a plan emerging. I ought to buy a new compressor as the current mobile one isn't well.

Might be an idea to pick up a 14cfm one like the ER14/50 in the link in the first post, then when I want to sandblast tee it in with the 200L 1.5hp compressor and end up with a 20cfm supply. Then for other things I can wheel the 14cfm compressor around without the need for air lines everywhere. Better for security too as I wouldn't fancy leaving anything expensive looking outside.

With the sandblasting stuff thrown in it should all come in at less than £400.

 

[rtbcomp]

That's the way to do it!

 

[snowcat]

Just an idea, Hydrovane, Masive Cfm, low pressure, cheep as chips.

 

[Wozzaaah]

Just googled for 'used hydrovane' and came across a guy called 'compressorman' who deals in them, this page makes for some interesting reading. He seems to know his stuff.

 

[malcolm]

I've ordered ER14/50 from Shiremore. Thanks for the link Wozzaaah. Oddly enough I had the old compressor running continuously for air grinding for an hour and a half this morning and it slowed down and stopped. Probably a duty cycle thing - oops

Not a fan of those KMS folk that sell the 20 gallon sandblaster thing - was daft enough to order one before finding out they wouldn't post to a work address. Should still be OK if their courier is half decent.

 

[Welderpaul]

grinding for an hour and a half this morning

Orrible!

 

[malcolm]

Wasn't so bad - found out that milling machine bits of a certain diameter fit into an air grinder - had to widen a circular cutout in an aluminium block.

Now I want a milling machine! Which type do the screw threaded bits screw into? Have rather a lot of them found in the bottom of my parts washer.

 

[snowcat]

Wasn't so bad - found out that milling machine bits of a certain diameter fit into an air grinder - had to widen a circular cutout in an aluminium block.

Now I want a milling machine! Which type do the screw threaded bits screw into? Have rather a lot of them found in the bottom of my parts washer.

British, Clarkson autolock type chuck on an int taper, not bridgeports.

 

[Welderpaul]

British, Clarkson autolock type chuck on an int taper, not bridgeports.

And morse taper with drawbar. You can get adapters Snowy

 

[snowcat]

And morse taper with drawbar. You can get adapters Snowy

Oh, i guesed you might, every machine i have ever bought has a diffrent set up, from every thing else. Its a bloady minefield, draws of tooling that fit just one machine grrr.

 

[Welderpaul]

Oh, i guesed you might, every machine i have ever bought has a diffrent set up, from every thing else. Its a bloady minefield, draws of tooling that fit just one machine grrr.

Mmm, a decent tooling set up to enable you to do most things costs as much as the machine. There are a few int taper clarkson autolocks on ebay at the moment - some at good prices. I paid a fair bit for a MT3 one a while back for the smaller mill.

 

[snowcat]

Mmm, a decent tooling set up to enable you to do most things costs as much as the machine. There are a few int taper clarkson autolocks on ebay at the moment - some at good prices. I paid a fair bit for a MT3 one a while back for the smaller mill.

Think I paid a couple of hundred quid for 3 chucks 2 30int and a 40, the trouble with it is buy a chuck with no collets etc is useless...I bought all me common turning tools new, went for the proper insert tipped tools dont regret that at all, .I need a set of keyway broches for a job comeing up but think il buy new, again i could buy S/H cheep and find there blunt, or missing half the sizes.