Sandblaster details

[CraigM]

I'm looking for a sandblaster. I've looked at a bunch of ads for them in Northern Tool and Grainger catalogs. I've seen them at the local farm store. Unfortunately, they were in boxes, so I couldn't play with them or I'd probably not need to post here. The answers I got there didn't all add up.

I read a bunch of old threads about them and I'm still looking, though maybe a little less entheustically. My primary use will be for cleaning rust and old paint off of farm implements, and maybe a tractor or two. Also used for cleaning welds and general scale off of metal projects prior to painting. It's not a full time job, so I don't need great equipment, and if they turn out to be as simple as they seem, I might just build something. They don't look like rocket science.

The things that I can't quite figure:

They all seem to have a nozzle, and some an airjet. Nozzles and jets come in different sizes to create different air flows. Sounds like the air/grit mixture goes through the nozzle. What does the jet do? The nozzle is just to direct the blast, sort of like a choke on a shotgun?

There are pressure and gravity/siphon feeds. The siphon would seem to be nothing more complicated than an airbrush that sprays sand rather than paint?

In a pressure unit, is there a seperate line and regulator to pressurize the sand and push it into the gun? If so, how much pressure in in the hopper tank?

The pressure unit is always stated to be faster and more efficient, and they use sand faster. Is the difference just that they are force fed sand and therefore throw more of it at a time to cut faster?

 

[kennyd]

First question everyone will need answered to help is what compressor do you have? That will determine what size/type of blaster you can operate effectively.

 

[CraigM]

I have a 5HP 2 stage Quincy. The tag says 15.something SCFM @ 175 PSI. Should be enough for a small sandblaster.

 

[GE222]

I would recommend the pressure type.

Siphon types are often times more temperamental.

You will find that with these low cost sandblasters the productivity will be slow.

A lot of time will also be spent re-filling them with sand. Sand that must be kept very dry. Having a nice clean hard surface like a concrete slab is a must. This way the sand can be sifted and re-used.

I bought a Harbor Freight pressure type unit about 10 years ago. I was disappointed with it, mostly due to lack of air. My compressor was much smaller than yours. I haven't used it since, mostly because I have had access to a large blast cabinet.

I have since purchased an industrial 7.5 hp unit rated at 175psi at 24.5 scfm. This will be used to supply a large blast cabinet.

 

[TCowner]

Craig, I hope I don't get in trouble here but I have a small sandblaster that I have never used that I bought a year ago. I paid just over $100 it. If you are interested I would take $50 plus shipping from SE Minnesota.

If I am in violation of the no posting of items for sale, the moderator should feel free to delete this post.

 

[ray66v]

I have a 5HP 2 stage Quincy. The tag says 15.something SCFM @ 175 PSI. Should be enough for a small sandblaster.

This compressor will run a small sand blaster as far as volume and pressure, the problem comes with the heat that will be created from running for longer periods of time. Then comes the water.

Without a drier, doing large projects like implements will be a problem. Especially during humid conditions.

If your going for a lasting result, I would use a chemical metal prep after blasting them. That would help mitigate the effects of the moisture in the air, on the bare metal.

 

[Western]

The one thing that actually makes a difference is CFM. with 15 cfm you will almost be forced to go with a cheap siphon type. At 15 cfm, it will be SLOW going and I personally wouldn't try something as large as a tractor. I have used a siphon style years ago with a 25 cfm and it was slow, but worked.

Pressure really has nothing to do with blasting, rather how many cfm's you produce to become the propellant. 15 might work well for the very small stuff you mentioned.

Side note..Buy the best respirator you can, don't skimp here..

We do this for a living, if you would like a picture of our 300# pot to see how the air is routed I could try to get one next time I'm in the shop. I also have an 80# pot made in 1944 that is simpler strong and works but, not as well as the new stuff. The difference in the two is the air application.

With the 300# er I could bore a hole in concrete running it with a 185 cfm, yet I can still fill a truck tire with air, VERY FAST..

Try a cheap system and see if it works for you. As already said, they can be finicky at times and moisture is a night mare if you run for an amount of time. You can get a 2 stage water kit for like a $100 or so, just 2 bowls basically with drying material/filter and trap drains.

 

[CraigM]

Ray: Tell me more about chemical prep. I've seen it talked about, but could never find out the particulars. If I'm going to go to the trouble and expense of sandblasting something, I will want to put the extra time and money into a lasting finish. What I've come to understand is it is an acid etching process that gets rid of the microscopic bits of rust that might still be there. What kind of acid? Where do I get it and at what cost? How do you put acid on steel and then get it back off without causing more rust?

Western: I've already got a NIOSH respirator that I use for painting and the like.

The expense of having it done is the driver for me wanting to get or build a blaster. Around here, sandblasting goes for $200/hour. I realize that I won't be doing it as fast as that guy, but I still think it will be worth it, and a handy tool to have. I'd like to keep it cheap in case it turns out to be a big mistake. Maybe making something would allow me to try it with minimal investment. That's why I was asking about the particulars that I did. I'm trying to get a feel for how the actual blaster works. I don't want to come across as ungrateful for all of your answers because they all give me something more to think about and another point of reference, but nobody actually answered the questions I asked.

 

[ray66v]

You can buy a bottle of metal prep at any body shop supply store, or order it from an internet supplier.

Each product works differently. Usually the process is brush it on, or spray it on with a spray bottle, wait a specified amount of time, and rinse with water. A coating will be left behind that will protect the metal and it will be ready for primer.

I prefer to avoid that whole process and start with a spray on etch, or etching primer. But, I have perfectly dry air, so I can.

If you want to do general painting without going broke, follow your metal prep with an industrial enamel primer, and paint.

That would be Rustoleum, Valspar, or what ever brand you can get locally.

If you use all automotive products, it will easily cost about 4 or 5 times as much.

 

[dcyrilc]

Ray: Tell me more about chemical prep. I've seen it talked about, but could never find out the particulars. If I'm going to go to the trouble and expense of sandblasting something, I will want to put the extra time and money into a lasting finish. What I've come to understand is it is an acid etching process that gets rid of the microscopic bits of rust that might still be there. What kind of acid? Where do I get it and at what cost? How do you put acid on steel and then get it back off without causing more rust?

Western: I've already got a NIOSH respirator that I use for painting and the like.

The expense of having it done is the driver for me wanting to get or build a blaster. Around here, sandblasting goes for $200/hour. I realize that I won't be doing it as fast as that guy, but I still think it will be worth it, and a handy tool to have. I'd like to keep it cheap in case it turns out to be a big mistake. Maybe making something would allow me to try it with minimal investment. That's why I was asking about the particulars that I did. I'm trying to get a feel for how the actual blaster works. I don't want to come across as ungrateful for all of your answers because they all give me something more to think about and another point of reference, but nobody actually answered the questions I asked.

I have an inexpensive HF blaster which I have only used a few times, but I will try to tell you what I can about it.

My air enters a regulator followed by a water seperator/trap. It then goes through a valve followed by a "T". from the "T", one line goes to another valve and then to the top of the sand tank. The other side of the "T" goes to a "T" at the bottom of the sand tank. There is a valve between the bottom of the sand tank and the lower "T" for turning the sand on and off. From there, it goes to the nozzel for spraying. The hose from the "T" to the nozzel is a very heavy reinforced rubber to handle the abraision of the sand.

Don't know if that helps, but it is how mine is plumbed. The only thing I can't remember for sure, is if the first valve is before or after the regulator and water seperator.