Sandblast nozzles and prep tips

Well I need that with sand blasting. I have purchased a cabinet model that came with various nozzle sizes but the instruction manual assumes you have previous experience in sand blasting - I don't. What do the various nozzle sizes do for you? Are they used for different medium, different surface finish, etc?? I am currently using glass beads as my first parts will be the carb halves.

Secondly, glass beads are not supposed to remove any of the base metal (from what I have found on the internet), does that mean it is safe for sealing surfaces like the parts of the carb that will mount the two halves. I am not going to directly blast these surfaces but over spray, etc.. may hit them.

Lastly, what surface finish is enough. I have removed all paint and have a shiny surface except for a few deeper dark (dark gray as opposed to light shiny gray) areas that are likely rust pitting places. I am going to use a rust remover/stopper (SEM rustMort) product prior to the painting process so is it necessary to completely prep the surface to all shiny new looking metal?

Thanks in advance to all who repsond and help teach me to fish (sandblast). I have 5 of these old irons lined up for restoration (Farmall A, M, W6, (2) oliver 70RC wfe)

I wonder if it will protect the surface as well and I sand blast a part or two at a time and then will collect enough to shoot with primer.

The different nozzle sizes are to accommodate different compressor capacities. The smaller sized nozzles will flow lesser amounts of blast media and consume lower quantities of air. The smaller ones will also be slower because of that. I don't know what sizes you have but if your compressor is rated less than about 10cfm, you'll probably want to use the smallest one provided. If your instructions don't give you an idea, then you'll have to experiment a little. You will know soon enough if you are using a nozzle that is too big - your compressor will run continuously and your pressure will continue to drop off as you blast. Sandblasting either takes a lot of air or is extremely slow.

I've never used glass beads but my tendency would be to not directly blast machined surfaces unless there is rust present that could not be removed by light block sanding. I wouldn't worry about any "overspray" of the media. Besides, those surfaces will get a gasket anyway, correct? You bigger concern should be to get all residual media out of the tiny passages in the carburetor bodies. Remove all jets and blow everything out well.

I'd avoid the use of the Rust Mort in your case since the manufacturer indicates to not use it unless rust is present. I'd blast a little more on the darker areas to see if they will clean up better. Or, you could consider a product like Picklex 20 that can be used on clean sandblasted surfaces as well as lightly rusted ones.

I also recommend a two-part epoxy for the best primer prior to your color topcoat. Just be sure you understand the time window associated with any epoxy you might use.

Rod

Thanks for the info. No my manual does not specify any hints on what nozzle to use but since my compressor is small (5hp 30 gal) I will take your advice. So far it has worked well but I will experiment and find the best one.

As far as RustMort, I know that it will not bond with surfaces free of rust, instead the instructions say to wash it off prior to priming/painting. What I did not know is that Picklex can. RustMort is what my paint supplier recommends so I went with it. They don't carry Picklex. I will see if a local supplier carries it.

And thanks for the advice on a primer. I am not there yet but will be soon as now that I am sandblasting, I will have a batch to prime soon.

I don't use the Picklex as a rust treatment at all. I have used it only to protect raw, sandblasted metal from flash rust until I can properly prime it. If I can epoxy-prime the same day as I complete the blast, I won't bother with the Picklex. This is the situation with me most of the time. If you can get your carb bodies to a "no noticeable rust" condition with your media blasting, I'd forget the acid treatment altogether and go right to epoxy prime, preferably the same day to avoid any flash rusting from humid air. There was a time years ago that I bought the argument that you needed an acid treatment for "microscopic rust" that you can't see. I have gotten away from that idea in recent years and prefer to use, wherever possible, a bright metal blast and direct epoxy prime the same day with no other pre-treatment. You'll get different, legitimate opinions on this however.

Rod