Author Topic: Sandblasting gun air nozzle  (Read 483 times)

Online AdeV

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Sandblasting gun air nozzle
« on: June 29, 2017, 08:00:41 AM »
A friend of mine has a sandblasting cabinet, 2 guns, and in both the inner air nozzle is worn out. New ones only cost £5 each, but he's very tight & resents paying that for something which will wear out again... plus, he wants to learn to use the lathe, so making a steel one seems like an amusing project.

Since you only seem to be able to buy brass nozzles, I got to wondering.... why? Does brass abrade more slowly than steel? Why not coat one with some kind of rubberised paint, since rubber seems to resist sandblasting with pretty much anything (I presume the media just bounces off it)?

Anyway, I'm going to make a steel nozzle out of some ghastly grabby steel I've got lying around just to prove the concept, but if anyone can shed any light on why brass seems to be the preferred material?

Also... seems like a good excuse to start working on the CNC lathe again. I reckon that with a bar feeder added, I could turn these things out by the bucket load, sell them for £4.50, I'd only need to make a few hundred and the lathe's paid for  :thumbup:

I'll just add that to the project list.... oh, seems the book is full, better buy another one!
Cheers!
Ade.
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Offline awemawson

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Re: Sandblasting gun air nozzle
« Reply #1 on: June 29, 2017, 08:34:15 AM »
Stack up some old carbide inserts and use the central hole as your nozzle - not a lot comes harder than those inserts  :thumbup:
Andrew Mawson
East Sussex

Online AdeV

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Re: Sandblasting gun air nozzle
« Reply #2 on: June 29, 2017, 08:51:28 AM »
Stack up some old carbide inserts and use the central hole as your nozzle - not a lot comes harder than those inserts  :thumbup:

I was reading somewhere else that carbide is the preferred nozzle & wears very slowly... but that was for the outer nozzle, not the inner one (the one that creates the venturi). Does that nozzle need to be nozzle shaped, or will a simple pipe shape do the job?
Cheers!
Ade.
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Offline awemawson

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Re: Sandblasting gun air nozzle
« Reply #3 on: June 29, 2017, 09:15:29 AM »
The venturi on my blaster is at the other end of a 25 foot pipe so the nozzle forms no part of the suction other than limiting flow  :scratch:
Andrew Mawson
East Sussex

Offline Ed ke6bnl

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Re: Sandblasting gun air nozzle
« Reply #4 on: June 29, 2017, 09:31:23 AM »
not sure what you are doing but ebay has some chinese guns with ceramic nozzles for about $15 and the replacement nozzles are cheap. they seem to work ok 
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Offline vtsteam

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Re: Sandblasting gun air nozzle
« Reply #5 on: June 29, 2017, 10:20:29 AM »
Ed, this forum is about making things. Even if cheaper, easier to buy.

Hence the name.

 :proj:
I love it when a Plan B comes together!
Steve
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Offline Ed ke6bnl

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Re: Sandblasting gun air nozzle
« Reply #6 on: June 29, 2017, 10:24:39 AM »
then make the cheap ceramic nozzles fit your blast gun.
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Online AdeV

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Re: Sandblasting gun air nozzle
« Reply #7 on: June 29, 2017, 10:30:37 AM »
The nozzle I am referring to is one like this:

http://www.ebay.co.uk/itm/401343384009

Not the ceramic nozzle which sticks out of the end of the gun...

The nozzle as above causes a low-pressure region inside the barrel of the gun which pulls the blasting media up the pipe. This also abrades the nozzle causing it to, eventually, hole, which then tries to blow the sand back down the pipe again.... with predictable results.

That particular nozzle is ludicrously expensive... apparently cheap ones can be had for £5.
Cheers!
Ade.
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Offline vtsteam

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Re: Sandblasting gun air nozzle
« Reply #8 on: June 29, 2017, 10:59:56 AM »
Ade, looking forward to your experiment!

To go back to your original question, I don't know why brass is used for that in the present gun. A couple of dubious guesses would be that some sandblasting uses might require that no iron (from the inner nozzle) reach the sandblasted surface for contamination reasons, or that brass doesn't rust from vac condensation, sand moisture (or gun storage) or that it's easy to machine a fine finish on it. The freedom from rust might be the most likely of the above, since the inside of the nozzle could get scaled up, where no medium (occasionally) hits it, and that's the part that needs to be smooth.

Brass seems to be universally used as jets and nozzles in carburetors (on my mind since I just rebuilt one on a Ford 3000 tractor for a farmer/friend) -- probably again for rust/pitting reasons, smooth finish, and non-seizing properties for removal.
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Offline Bluechip

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Re: Sandblasting gun air nozzle
« Reply #9 on: June 29, 2017, 11:50:04 AM »
The nozzle I am referring to is one like this:

http://www.ebay.co.uk/itm/401343384009

Not the ceramic nozzle which sticks out of the end of the gun...

The nozzle as above causes a low-pressure region inside the barrel of the gun which pulls the blasting media up the pipe. This also abrades the nozzle causing it to, eventually, hole, which then tries to blow the sand back down the pipe again.... with predictable results.

That particular nozzle is ludicrously expensive... apparently cheap ones can be had for £5.

Ade

When I had my Guyson Bead Blaster the nozzles were hard steel and used to wear out where the bead hit the side as you say. I used to make my own from mild steel 'cos they were a lot cheaper.  :beer: Not so durable. Can't see why brass should be better.

I once made one from delrin ( well polyacetal ) and it seemed to last reasonably well for the reason you mentioned with rubber..

Not sure whether that one is overly expensive, I seem to remember the Guyson item was far from cheap ...  :scratch: for some reason.

This was in the early '80's.

Dave.   
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Online AdeV

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Re: Sandblasting gun air nozzle
« Reply #10 on: June 29, 2017, 03:10:12 PM »
Cheers guys  :thumbup:

I realise the guns are cheap enough, but it seems a shame to throw away a perfectly functional gun just because a removable nozzle has worn out...

I started to make a steel one, but I realise I've cut the (rather lovely) taper, and left myself no safe way of holding it in the chuck! Doh! So I think I may buy some hex bar, and try again. Hex bar has the advantage I don't need to dig the mill out to make the flats...

I'd wondered about making a steel (or brass) one, then painting it in some kind of rubberised paint; or even wrapping it in a little EPDM glued on with some kind of super-sticky glue. In theory, if one kept an eye on it, as the rubber wore through (assuming it does), then one simply peels off the rubber sheet and sticks on a new one... I reckon it'd cost less than a £penny in rubber & glue...

Still, now I have a good reason to work on the CNC lathe. What do we reckon, about 100/hour production should be achievable, sell them on eBay for £4, after material/leccy/tooling costs that's got to be £3 profit...
Cheers!
Ade.
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Offline vtsteam

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Re: Sandblasting gun air nozzle
« Reply #11 on: June 29, 2017, 03:51:47 PM »
Well if there's the demand.......mailing out 100 can take a lot of time, however. 

Packaging, stamping, addressing and putting in the mailbox even at 15 minutes/order and a minimum purchase of 2, yields 12.5 hours of reaaaaallllllyyyy boring human time to add to that 1 hour machine time.

Not wanting to discourage you, however, because I'd like to see you make the darn thing!
I love it when a Plan B comes together!
Steve
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