What do you use for grit?

I have not tried sandblasting grit. I recently ordered 50 lb. of 60/90 silicon carbide (rough) grit and it cost $95 including shipping and handling. That's the cheapest I've found so far (from Miles Supply - I can provide a link if wanted).

Well, in researching the sandblasting angle. I have found several local suppliers of sandblast media that also carry aluminum oxide and/or silicon carbide. They are all under a dollar a pound when buying 50 lbs or more. I found one place that quoted me 55 cents a pound for the lower grits of aluminum oxide in 50 lb bags.

So to kinda stick with the subject, but change the question. What do you like better, aluminum oxide or silicon carbide and why?

Hi and Welcome!

I grappled with the cost too, but had to opt for the "real deal" SiC as the only route to a happy shine, however, regarding the discussion and conjecture, this is why AO don't cut the mustard...

Under a microscope you can see the tiny grains themselves, first up Aluminium Oxide, and secondly the Silicon Carbide.



As you can see - the particles have a particular shape, and although they break down in the tumbler with the action of the rocks, they also maintain a similar shape, just in smaller sizes. The Aluminium Oxide is slightly rounded odd shaped particles, and as such has a gentle action, and acts really well as a final polish in the finer grades.

On the other hand, Silicon Carbide as you can see has very sharp pointed fragments, and even when broken, these particles continue to have sharp edges and points, and as such always present cutting faces when the rocks are tumbling in the barrel. Excellent cutting action.

Hope that insight helps - sorry there isn't a cheaper option

Cheers,

Sparkles.

Wow, that really helps, thanks. I just checked my order from Rockshed.com and I ordered the 60/90 in SC, the 120/220 in SC, but the 500 and polish are AO. So I guess that is what I'll be using for the first few loads anyway. Some of the sandblast supply places had SC in various grits up to 250. It was still less than a dollar a pound for 50 pounds or more. Would 60/90 SC grit for tumbler be the same as 60/90 grit for blasting? If so, that's a nice discount on the cost right there. The 5 lbs I bought from rockshed figures out to be 2.50 a pound for both the 60/90 and the 120/220 grits.

I don't expect perfection in the first couple batches. I do expect it to turn out better than the two batches that went through the cheap toy tumblers. And that isn't expecting very much. All those did was knock off the edges and give a dull finish.

On a positive note, I just finished my homemade tumbler and I have 3 lbs of rocks tumbling right now, with no grit, but tumbling anyway. As soon as the grit arrives I'll get going for real. Until then, this will give the tumbler a nice test and let me know how I can improve it. I already have a few changes I want to make on it, but since I have already tore it apart and rebuilt it 3 times, I'd like to tumble some rocks before I tear it apart again.

syfun: the regimen you described (60/90 SC, 120/200 SC, 500 AO, AO polish) is standard. That should work out just fine for you. How about posting some pics of your homemade tumbler?

Here goes a try for the pics. I just went out and after about 3 hours, the motor overheated and failed. I'll let it cool down and it will start rolling again, but that just means I need a new motor. That's why it's the "old" furnace motor. It failed on the furnace and was replaced. Anyway, here we go with the pics:

This is it in it's entirety. Like I said earlier, I already know some improvements to make like putting the switch in the box like it was intended, taking out the casters and putting in a full length bar. Any suggestions are welcomed.



This is it without the barrel



Here are some of the barrels I made. I glued some strips of PVC insite the barrels to help tumble the stones. I'm not sure if it is the right idea or if they will even hold up, but it seemed like the right thing to do at the time.



Here's a closer pic of the barrels.



Let me know what you think.

Hard Rock Cafe: So how did the strips on the inside of the barrels hold up? The tape was from a previous build, the other barrels don't have tape on them. I put some clear rubber tubing over the shaft, you can see where it stops about 5 inches from the pulley. It works great for turning the barrell, the rpm's are a bit high at 84 but I have to get a different motor anyway so I'll see what that turns up.

Thanks
Steve

My strips weren't as large/thick as yours, and they did wear down a little, but still do the job.

I couldn't tell that was clear hose; I thought your shaft changed diameter. That should do the trick!

Chuck

Well, for an update, The grit was on the front steps when I got home tonight. The motor has holes in it to oil the bearings, so I repositioned it so they were on top and put some oil in. I also added brackets to the back of the motor and lifted it about half an inch off the wood, it was setting right on the wood. I removed the tape from the barrel and set up my first batch of rocks. It has been tumbling for 3.5 hours now, the motor is hot, but it is still running. I'm going to grab some aluminum heat sinks I saved from some old computers and glue them on the moter to help with the heat.

I also want to say a big THANK YOU to everyone out here. I have gained so much by reading your comments here and on other threads.

Thanks
Steve