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Discussing sand blasting odds and ends

Just a Sparky

Hot Rolled
Joined
May 2, 2020
Location
Minnesota
Got a couple things on my mind here pertaining to sand blasting. Apologies if this is a bit of a ramble.

I recently upgraded my blast cabinet with a Skat S-35 siphon gun. I finally get consistent siphoning of media now. But I find myself burning through steel nozzles at an astounding rate. I get 30-45 minutes of blast time with 80 grit aluminum oxide before they wear completely through and disintegrate. And I get nowhere near the 38 seconds claimed to clean a 6x6" area. More like 5-7 minutes.

So there are three things I see that I can change to remedy this and I'm curious for your guys' input on them;

-Upgrading from 5/16" steel nozzles and jets to a Hi-Pro power head with carbide nozzle (TP Tools: 6300-92)
-Changing from aluminum oxide media to silicon carbide.
-Upgrading from 3/8" hose & 1/4" fittings to 1/2" hose & 1/2" fittings.

Is there anyone here who has used the Hi-Pro head to comment on it? I'll have a 10 horse pump running soon enough so the CFMs won't be an issue.

Is silicon carbide a good choice for rapid, aggressive cleaning of tenacious filth on cast iron? I find that flat, machined surfaces are easy for almost any media... but things cling to the rough, porous surface of cast iron very persistently. Are there better options for this work or am I on the right track? I've heard mention of steel grit and steel shot being used too. Would either of these be suitable?

I plan to upgrade to larger hoses and fittings because I feel like I am getting excessive pressure drop between the tank and gun nozzle. The difference between 5/16 and 1/4" orifices is not that great. I imagine there is a great deal of expansion going on every time the flow is directed through a 1/4" type 'M' connector.

Thoughts on these ideas? :scratchchin:
 
I use a boron carbide nozzle and it is just amazing how little wear after hours of blasting with sharp silica sand. These nozzles are a little expensive up front but save a lot of money in the long run. They last several times longer than silicon carbide. The only downside, other than a little higher price, is the brittleness of the material. The ones I use come cemented into a form-fitted aluminum case. I'll never go back!

The company that made mine:Boron Carbide Nozzles & Inserts | Malyn Industrial Ceramics Inc. has a wide variety of sizes and venturi styles, but you might have to do some adapting to get one to fit your gun.
 
Why a quick disconnect at all ?

I think you need to step up to a pressure set-up.

TIP did offer a kluged up rig to doo this (took the 38 special pressure blast valve,
put it on the bottom of a 99r tank, and added a foot pedal). But no longer is it offered.

I have never used silicon carbide, rather simple fine sand, as fine as you can get.

You should be running ceramic nozzles at the least. I'm surprised TIP sold you that gun
with a steel nozzle, and I'm surprised you got that long of life from one.

When you say "Tenacious" doo you mean several coats of hand brushed on paint ?
Rubbery materials are the hardest to blast.
 
Yeah, about 100 years' worth of brushed-on paint and primer turned rotten with grease, oil and rust. Some corners or thick spots where the stuff welled up to form a little bead take several seconds or even a minute or two of continuous blasting to erode. Makes for several hours of blasting to get the whole project done.

IMG_20201205_180025908E.jpg

Quick disconnect because of shop layout. The cubby my blasting cabinet sits in also doubles as ladder storage. Can't get ladders in/out with the air line connected. Can't get the cabinet door 100% open when ladders are stored in front of it. My shop is a little cozy.

Skat sells steel nozzles with their guns by default. Finding the ceramic and carbide stuff takes a little doing since they only list part numbers for steel nozzles on the care sheet that comes with the gun. I'm surprised they don't sell CBN or equivalent.
 
I bought a Skat cabinet over 25 years ago. I'd be glad if I never blasted anything ever again. It's been a POS from Day One.

As for blast time....your experience is 'real'. The times they advertise are fantasy.

IMO the trick to good blasting is dry, dry, dry air. And that is just as difficult to get as the cabinet. More costly, too.

I guess if I had to blast every day I'd lay out the money for good compressor - probably a centrifugal type - and a good drier. I'd accept the fact that they are expensive to buy, power, and maintain.

Then there's the PITA of the vacuum/bag used to keep dust out of the air....

And yes, the nozzles wear down fast.
 
In lieu of a full-on drier, I'll admit the idea of water cooled aftercooler before my tank is very appealing. Nothing like holding onto a blasting gun that feels hot enough to boil water.

I imagine I could build one easily enough with some copper sweat fittings. Wouldn't take up much space if mounted in an otherwise disused wall space. Condensation would go right into the tank to get drained off at my convenience. Hook up a garden hose and good to go.
 
J a Sparky, is the compressor in the photo the one you blast with? I can't imagine using a 5/16 nozzle with just that much air. Have you tried going with a 1/8" bore? You can up the pressure/velocity while reducing the CFM and get better cleaning. Naturally, you get a smaller 'active spot', but anything that will fit in a cabinet can be efficiently blasted with the smaller nozzle.

edit: If you're only willing to use nozzles made to fit your gun, you won't have a lot to choose from. Adapting another type usually isn't a huge deal for a machinist.
 
Lol, no. That's the antique Brunner I'm working on restoring. Hah! That little half-horse is nowhere near suited to blasting.

When my work is done I will have two pumps and one tank.

This 10 HP 'skid' unit as my high CFM workhorse: Video

...And the 1/2 horsepower antique Brunner pictured above as a low CFM 'maintenence' pump for novelty and convenience + central reciever tank. (I have to roll out and connect a coil of S.O. 'cheater' cord for 240V, 50A power.)

Currently I'm relying on 4.5HP worth of small pumps working in tandem for blasting, which is less than ideal. Hence the big continuous-run Quincy skid unit.
 
Got a couple things on my mind here pertaining to sand blasting. Apologies if this is a bit of a ramble.

I recently upgraded my blast cabinet with a Skat S-35 siphon gun. I finally get consistent siphoning of media now. But I find myself burning through steel nozzles at an astounding rate. I get 30-45 minutes of blast time with 80 grit aluminum oxide before they wear completely through and disintegrate. And I get nowhere near the 38 seconds claimed to clean a 6x6" area. More like 5-7 minutes.

So there are three things I see that I can change to remedy this and I'm curious for your guys' input on them;

-Upgrading from 5/16" steel nozzles and jets to a Hi-Pro power head with carbide nozzle (TP Tools: 6300-92)
-Changing from aluminum oxide media to silicon carbide.
-Upgrading from 3/8" hose & 1/4" fittings to 1/2" hose & 1/2" fittings.

Is there anyone here who has used the Hi-Pro head to comment on it? I'll have a 10 horse pump running soon enough so the CFMs won't be an issue.

Is silicon carbide a good choice for rapid, aggressive cleaning of tenacious filth on cast iron? I find that flat, machined surfaces are easy for almost any media... but things cling to the rough, porous surface of cast iron very persistently. Are there better options for this work or am I on the right track? I've heard mention of steel grit and steel shot being used too. Would either of these be suitable?

I plan to upgrade to larger hoses and fittings because I feel like I am getting excessive pressure drop between the tank and gun nozzle. The difference between 5/16 and 1/4" orifices is not that great. I imagine there is a great deal of expansion going on every time the flow is directed through a 1/4" type 'M' connector.

Thoughts on these ideas? :scratchchin:

You might run 2 of the 1/4" hoses in tandem since it is not something you run all day every day
 
Say, another question:

What's a good quick disconnect standard to adopt for 1" air lines? I'm going to need to connect my skid unit to my receiver with no less than a 1" flexible hose.

(Being able to rapidly disconnect equipment and roll it around on casters is extremely convenient for maintenance and housekeeping.)

Something like these 'universal' twist-locks perhaps?

Z2o2HyjcpEx_.JPG
 
Right now, the oversize steel???? nozzle is your biggest factor.

It takes about 6 - 7 HP to run a 1/8" nozzle without the compressor gradually losing the race to keep up at 90 - 100 PSI
10HP will almost run a 3/16" nozzle.

I don't blast that often but have a 1/8" tungsten carbide nozzle on the cabinet/siphon blaster. They are supposed to last at least 10x what a ceramic nozzle does. Old fashion ceramic nozzles are used on the pressure blaster my wife uses in the great outdoors for blasting rocks. They don't last all that long. Several 100lb tanks worth and they are noticeably larger.

I was running a 5HP IR T30 + a 7.5 Kellogg in parallel for the pressure unit. The IR motor died, and the 7.5 Kellogg is just about adequate for the blast cabinet with the 1/8" nozzle. It runs constantly while blasting, but only takes a few minutes to catch up and shut down when i put the gun down.

Put garnet in the cabinet maybe a 1/2 dozen years ago and hardly used since. Was using it for first time in years over the weekend. One nice thing - it never packed up like sand used to in the humid cellar conditions.

good luck!

smt
 
Say, another question:

What's a good quick disconnect standard to adopt for 1" air lines? I'm going to need to connect my skid unit to my receiver with no less than a 1" flexible hose.

(Being able to rapidly disconnect equipment and roll it around on casters is extremely convenient for maintenance and housekeeping.)

Something like these 'universal' twist-locks perhaps?

Z2o2HyjcpEx_.JPG

Yes.

poke around in here, should answer much.
Sandblasting & Abrasive Blasting Equipment & Parts | Indianapolis, Indiana | IDS Blast
 
Whoops, I did say 5/16", didn't I?

D'oh!

5/32" jet.

:wall:

Single stage 10 horse rated for around 35CFM rather than a 2 stage limited to around 25-ish.
 
Sandblasting is such a PITA waste of time.

You're cleaning greasy painted machine parts?

Sandblasting may not be the right process for you.

You need a few heavy wire or perf baskets. Fill them up with your junk, fasteners and all. Separate out the aluminum and zinc parts. Take these down to your local engine rebuilder and have them run through their wash cabinets. Anything that needs to be removed will be gone and the parts will be ready for whatever is next.

This should not cost very much.

I have about a dozen wire baskets that are made for this. They are 12x24x 6" deep with handles. When I tear something apart the pieces go straight into the baskets.

I had a nice older ICM cabinet for about 15 years. I grew to hate it and sold it to a friend with a foundry. Years later I bought a similar cabinet and gave it to my father in law for Christmas as he restores 20's cars and he was using some cheap junky cabinet. I might need a handful of small part blasting in a year. I give those pieces to him and done deal. At the same time, I probably have 5-10 of those wire baskets worth of parts washed up every month. That's probably a $200/month total expense. This is machine parts, way covers, engines, transmissions, differential housings, you name it.
 
Umm....blasting is sometimes used for cleaning but it's also used to provide a proper anchor profile for painting. The auto shop parts washer won't do that. It also won't do a thorough job at removing old paint or rust.

Many industrial finishing specs require blasting to a defined SSPC profile. No way around that.

Then, the local auto shops around here (Houston) are loathe to mess with anyone's greasy parts. Even more, they might wash greasy parts, because that's what they deal in every day, but they sure don't want layers of old latex paint in their washers. And they ain't cheap. Hell, it's a pain in the ass just driving there and back.


As for nozzle size...my Skat cabinet won't flow through a 1/8" nozzle. It needs a nozzle of 5/16 or so in order to pass any abrasive with any velocity. It'll clog otherwise. If I run an abrasive fine enough for it to flow through a small hole, it is too fine to be useful.
 
Umm....blasting is sometimes used for cleaning but it's also used to provide a proper anchor profile for painting. The auto shop parts washer won't do that. It also won't do a thorough job at removing old paint or rust.

Many industrial finishing specs require blasting to a defined SSPC profile. No way around that.

Then, the local auto shops around here (Houston) are loathe to mess with anyone's greasy parts. Even more, they might wash greasy parts, because that's what they deal in every day, but they sure don't want layers of old latex paint in their washers. And they ain't cheap. Hell, it's a pain in the ass just driving there and back.


As for nozzle size...my Skat cabinet won't flow through a 1/8" nozzle. It needs a nozzle of 5/16 or so in order to pass any abrasive with any velocity. It'll clog otherwise. If I run an abrasive fine enough for it to flow through a small hole, it is too fine to be useful.

I've been doing it this way for more than 20 years. In every different place I have lived all over the NW and Chicago area. If you're an inconsiderate asshole and bring a gearbox packed full of grease without wiping out the grease with a few paper towels first, then, yes, you're going to be told to fuck off. I guess I should have mentioned you should be a decent human human being if you want to interact with others in mutually beneficial commerce?

You are correct that caustic soda does not take off much rust, but you are very wrong about the paint. Caustic soda removes all paint if you want it to. I'm not that picky about a layer of paint that doesn't come off after washing. If it stayed on through that it's good enough to paint over. I explain the cleanliness needs of the parts I'm dropping off on delivery. The shop that does all my cleaning currently understands that it's a "Best minimal effort" deal unless I state otherwise. In other words, run it for 1/2 hour and steam clean it off. I'll do the rest which is usually nothing.

As far as paint prep goes I think you're getting far outside the scope of what a blast cabinet does. A blast cabinet is used for small part finishing. They are almost always used with glass bead, stainless steel shot or walnut shells to fine finish parts. Using a cabinet blaster to remove grease and paint is the wrong thing to use it for.

I have tons of stuff sandblasted. I send it out and a guy in a supplied air suit waving a wand fed with 200 CFM of dry air and sand makes these parts ready for paint and PC.
 
Is silicon carbide a good choice for rapid, aggressive cleaning of tenacious filth on cast iron?
I have in Real Life used silicon carbide. A friend who does lots of hard facing on cast iron has two blasters, one with beads and one with carbide. That's a sensible setup.

The carbide rips away material like nobody's business. Internal splines commonly shrink a bit in heat treat, you can remove enough material carefully with silicon carbide to make them fit again. With beads or sand kiss that idea off, it'd take a week. Silicon carbide makes regular sand look like kids' stuff. As Garwood points out, using it on paint and the like would be a no-no but for ripping slag off cast iron, it kicks ass.

Here comes thermite out of the woodwork but one thing about it : static electricity. Ground wire on the parts and gloves without even a tiny hole and you'll be okay but get a touch careless and it'll teach you what Ben Franklin learned - electricity will wilt your pecker and put you on your ass like right NOW ! Beads have never done that to me but silicon carbide, once almost every time I ran it.

I have no idea if it's right for your job, but the stuff removes metal fast. You almost can't use it for regular blasting, so don't think "I can just give it a light going over in the carbide blaster." That wouldn't be practical. You'd need two, if you intend to do any regular bead blasting.
 
It's not an issue of being an asshole...it's an issue of life in 2021. Most shops have a keen sense of what makes money and what doesn't. They shun any work that doesn't fall into Category 1. So...they might take in your greasy parts but it sure won't be cheap. By the time you drive to their shop, wait, then drive back....you've invested a lot of time, effort and money. It works well for an entire engine, but for a pair of valve covers? No way. Way too much intercourse required.

A cabinet blaster is simply going to outclass a parts washer when it comes to surface prep and removal or rust and paint. I have both. Let's assume you are rebuilding a 1960's engine and you want the valve covers and timing cover ready for paint....the blaster is the only way you'll end up with a proper surface. That is, if you are doing high-end work and not an R&R job.

A blast cabinet can handle small jobs piecemeal. Trips to the auto store will eat you alive.
 
I have in Real Life used silicon carbide. A friend who does lots of hard facing on cast iron has two blasters, one with beads and one with carbide. That's a sensible setup.

The carbide rips away material like nobody's business. Internal splines commonly shrink a bit in heat treat, you can remove enough material carefully with silicon carbide to make them fit again. With beads or sand kiss that idea off, it'd take a week. Silicon carbide makes regular sand look like kids' stuff. As Garwood points out, using it on paint and the like would be a no-no but for ripping slag off cast iron, it kicks ass.

Here comes thermite out of the woodwork but one thing about it : static electricity. .

The mix in the blaster matters so much more than nozzles.
And then pressure which is so often dialed up to high.
Add the love of pokes through the gloves. What the heck is that?
It seems so simple and straightforward.
Glass, alumina oxide. silicon carbide percentage and so many grit sizes in the mix and one can go crazy.
Bob
 








 
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