Tumbler vs. sandblasting

[alexkuzn]

Guys,

will a tumbler from Harbor Freight be a good substitution of a sandblasting setup for folders blades and titanium liners?

Thanks,
Alex

[David Broadwell]

Alex, I'm not 100% certain, but I would think a tumbler would not be a good substitute for sand or bead blasting. I'm sure you are going to have to get some sort of heavy tumble medium, whether it's steel shot in verious shapes or some other material. You'll also have to load it with an abrasive compound. Tumbling can take a long time, but at least you could probably load your tumbler with parts and let it run overnight. I don't so much recommend sandblasting as much as beadblasting. It's much quicker. Just put your parts in the cabinet and close the door, blast them, then take them out and assemble the knife. That's 5 minutes verses all day.

I did put a couple of scraps in my cartridge case tumbler once, but it didn't do anything. I guess pecan shell media and Brasso isn't the best for titanium!

David

[alexkuzn]

Bead blasting is nice. No questions about that. But with air compressor and a cabinet it quickly runs to $800 or so.

[Ray Rogers]

Depending on the medium used tumbling could also round the edges on your parts. Sandblasting puts little dents in the steel which can hold moisture against the blade. That can be bad for carbon blades on using knives. Bead blasting does the same thing but on a much smaller scale and works well for collector's knives. On a using knife a bead blasted finish doesn't seem much more durable than anodizing to me.

Harbor Freight has some very small sand blasting rigs, just a nozzle with a glass jar attached to hold the sand or beads. These can be used for really small projects like knife parts, I use one to touch up a sand blasted finish that hets scratched after the knife is finished. You'll need a small compressor
in the $150 price range to run this little sprayer. Build a cabinet out of a carboard box to catch your blast media for recycling and you're good to go ...

[NJStricker]

I reload rifle and handgun cartridges, and judging by the appearance of my brass when I remove it from my vibratory tumbler, I don't think you'd like the result. For cartridges we generally use ground corn cob or walnut hulls, softer then you might use for titanium or steel, but then again the cartridge brass is a softer metal. The purpose for tumbling is to clean burned powder residue off the cartridges, and if you want, you can add a solution to the tumbling media to polish the brass. However, my experience is that the "finish" on the brass is uneven (assuming this experience would translate to knife parts). Without the polishing solution you can get a dull matte appearance, but sometimes scratches also (from the walnut media or from other cartridges--depending on the size of the cartridge you can tumble 50 to 500). And Ray is right about rounded edges. Reloaders who tumble their cartridges have to do so before removing the used primer, otherwise the tumbling media can enlarge the primer pocket, which can result in a dangerous situation. Consider also that when you bead blast, you can be selective about which sides you want to blast, and mask off certain areas or whole sides. The tumbling media isn't selective--it will abrade any masking material, and abrade or round the surface you plan to fit against the tang.

[alexkuzn]

I checked my local Craig List/ There are a lot of used air compressors for sale. What parameters I should look for in a compressor that will serve me in a long run?
I remember reading that I should avoid some type. Can't remember what was that exactly.

Thanks,
Alex

[Ray Rogers]

In that price range, I don't think there's a lot you can avoid. If you buy a compressor who's original price was about $150 you should have enough for running that little sand blaster. Will it serve you in the long run? Who can say? That depends on what else you decide to do that needs a compressor. Generally speaking, there aren't many knife making jobs that require a compressor but, for those that do, these little compressors are marginal at best. They won't run a full sized blast cabinet, a Dozier grinder, or a vacuum table. They will - barely - run a mist sprayer, a die grinder, or a cut-off tool ...

[alexkuzn]

Ray,

what would be good specs for a compressor that is used just for sandblasting? (HP, PSI etc.)
My budget for used compressor is $150.

[Ray Rogers]

Any compressor that sells new for about $150 would handle that little sprayer I mentioned before. For a regular sandblast cabinet, the compressor requirements would be dictated by the cabinet. Most of them require 7 to 10 cubic feet of air per minute delivered at 90 psi in order to get continuous operation. That takes a fairly large compressor. But, even a $150 compressor can deliver 90 psi, it just can't deliver the requierd cubic feet of air for very long before the compressor has to cycle and pump itself up again. So, with a small compressor you would spray for a few seconds, wait for the pressure to come back up, spray for a few more seconds, etc ....