The Stovebolt Site Forums The Shop Area The Tool Chest Calibration help please

Was blasting some small engine parts in the cabinet today. About 70 psi with alum oxide (fine grit). Things like the stomp starter, and bell housing cover plate (probably wrong name, but you guys no what I'm talking about). 70 years of rust and grime and it took about 10-15 minutes with cracks, etc for each. Seems too slow. To calibrate, how long would it take you guys with cabinets to clean a 2x2 in sq. flat metal with paint and rust.

Sounds about right. Not enough pressure with a suction feed system to really do any serious sand blasting. It works OK for paint and light rust, but anything more than that and you're going to be there a while.
Carl

It would take less than 2-5 minutes or less in my cabinet, depending on the paint (both sides of a 2x2 plate of metal). I'll check the pressure setting, but I would guess between 60-80psi.

That's about what I'm seeing Tim. What media are you using?

I use a mixture of fine alumina and fine plastic beads. I think that TP Tools calls it SPEED BEAD ABRASIVE: "80 grit Aluminum Oxide abrasive for fast cutting and 50-80 grit Glass Beads"

http://www.tptools.com/Speed-Bead-Abrasive,352.html?b=d*8019

The industrial blasting firm that does big jobs for me has been willing to buy bags of those media for me (I mix them 50/50).

I try to clean all grime/grease off before placing parts into the cabinet.

2x2 both sides? Less than a minute. We have probably 100 psi+ at the cabinet with 54 grit garnet. We did have glass bead but it makes way too much dust. Add that to dirt and rust and it gets really hard to see. I really prefer the garnet.

120 psi less than a minute, 70 psi about the same time you are talking. Pressure is a wonderful way to regulate the process.

Thanks Fellas. Today blasted the fan, the paint and primer for a 2x2 both sides at 80 psi w/alum oxide would be less than a minute. What takes time is the deep imbedded, I think of it as microrust (I don't think that is a real term, but should be), that is very fine and darn hard to clean. That stuff takes another 2-3 minutes to get down to bare metal.

Also, how do you guys know when it is time to change the nozzle.

Allen.. you never change the nozzle because you get a Carbide one. They are $50 or so for one nozzle, but I got mine about 15 years ago and its still just fine.

I had all of these problems before I went to the media I use now. Micro rust, or any anomalies come off at the same speed everything else does. I dont think this has as much to do with the media as it does the higher pressure? Bet its a combo of both.

http://devestechnet.com/Images/Restorations/1950B/D50b02015lg.jpg

That is my compressor setup. Its two EL Cheapo single stage 60 gallon compressors in tandem. I can run my blast cabinet all day with that setup and get no less than 100 psi. Less than that? You are waiting about 15 minutes for the compressor to build back to 100. Hope this helps! Holler if I can help!

Keep a spare carbide nozzle. Compare the aperture/opening of the nozzle you are using next to the spare nozzle.

I have replaced my carbide nozzle once in 6 years, but I do not regularly use my blasting cabinet.

I use it almost every day, but the way I tell if the aperture is a problem is if the compressor can no longer keep up. So far so good. But good advice. I have another one too. You never know.

I then ordered a carbide nozzle from sandblast-nozzles.com (part no. TL2-1) in the 3/32" size. The 3/32" is really the best size for the sand I use and the pressure I need.

excerpt taken from my shop how-to section. Hope that helps!

I used the ceramic nozzles for while but if you don't watch it, not only will the nozzle go bad but the siphon gun as well. I finally spent the money and got me a carbide!

I've got a carbide nozzle, but I think it is too big for my media. I'll eventually get it dialed in with you guys help. Much, much better today, 20 psi increase made a huge difference. Put the rusty ole bell housing in after a quick scrub in the parts washer, and it went very fast. Even sprayed some epoxy primer on 8 or 10 cleaned up engine items. It's been so wet here, haven't been able to ride the horses, so making some progress on the truck.

I traded my horses and the accompanying shovel for a blast cabinet. Have never looked back!(get it?) I am breakin myself down here!

Anyhow, the 3/32 carbide nozzle made all the difference for me. Before that, I ruined a few siphon guns because I didnt change the ceramic nozzle fast enough. If you need justification for getting a $60 nozzle, you can do a really good job on horseshoes too!

Glad you are getting it all dialed in Allen!

I run about the same pressure and same grit. But like you some days take forever to clean a small item.
I tried pressure 60-85.

What I find is the pick up tube and where to feed hose goes into the gun get clogged.

Material is not old enough to be dirty but does seem to lump.
As Arizona is dry it is not moisture. so maybe static.

If I jam the pick up tube up and down and wiggle it some thing it clears and clean for 15 minutes or so, other days I need to keep wiggling it.

If that does not work then a quick disassemble of the gun tapping out the clumps and I am back running.


May I will bump up the pressure and try some of that speed abrasive mix.

I am starting to lean toward electroplate for the micro rust, keeping the blasting for paint.

On my cabinet, if you place your thumb over the nozzle and hit the air pedal, it will blow back through the pickup hose and clear any obstructions. All in a matter of seconds.

Yup. Thats a good Tip Mark. Works everytime.

I blast at 40psi using Black Beauty and a 2 sq/in section would take about 20 seconds. Unless the OP meant 2sq/ft High pressure just shatters the media faster making dust - "2x2 in sq."

Al oxide really isn't the right media for rust... paint only, yes. Surface rust, getting iffy.

50lbs of Black beauty is $8.. change it when it slows down.

I use 1/8th in ceremic tips. At the low pressure I run they are good for a few hours. I would go carbide if I did blasting for a living, but just for one or two trucks ceremic will be fine.

Eastwoods
Popular Mechanics

It may not be the best material for removing heavy rust, but it removes rust and leaves a smooth paintable surface - smooth compared-to more aggressive and larger-grained rust-removal media.

Comment to original poster: you might want to consider removing grease and grime (and as much paint as possible) with solvents and/or paint remover before blasting, especially if you are blasting in a cabinet.

I use alox in my big old honking KELCO blast cabinet and it works fine. I use a boron carbide nozzle for alox in the cabinet and switched the ceramic in my pressure sandblaster to tungsten carbide and made a big difference. Not cheap but minimal wear so far.

Having the right equipment for sandblasting sure makes a difference. I built a fairly large sandblast shed with a King industrial air extraction system and use a full Clemco mask/breathing system. youngest son is blasting his 240z and actually enjoys it. A long ways away from 25 years ago when I was blasting my 55 Belair with minimal safety gear. I hated it.

That PM article is pretty funny... and here is the punch line:

"The last section shows why aluminum oxide is the 800-pound gorilla of blasting media"

No, no its not. There are many, many more aggressive types of media and grits that will make al ox look like you are slapping the rust with a wet noodle. Coal slag (aka black beauty) is the cheapest and fastest one that is readily available.

Also 50lb of Al Ox will set you back $50 or so per 50lbs (Eastwood wants $70 PLUS shipping!). Black Beauty is $8 for 50lbs.

There ARE times when you want to use less aggressive media for rust... thin metal and final surface texture being the biggest reasons.

If you ware warping or burning through metal panels its not the media's fault, its the operator and the setup that's making the mistake.

That's a ridiculous price for al ox. You need to find a commercial supplier, may have to drive a little farther so just stock up on your favorite media. I get al ox for about $15 for 50 lbs, about the same for glass beads. About $8 for coal slag (BB), nickel slag (Green Beauty).