coloradocliff i have 6" PVC barrels with 4" PVC openings. So 4" wide is the widest big rock, but it can be up to 5" long or 7" to 8" long. rocks about 6" get jammed or have crappy action.
i run 3/4" to 1.5" rocks with one big rock that is a fat 4" like 2 pounds. 1 to 1.5 pound rocks can be run with a mix of bigger tumbles sat 1" to 2.5".
if the big rock gets close to 5" or 7" to 8" in length i run smaller 1" rocks.
the small rocks are target tumbles. a pile that range from 3/4" to 2.5" that are kinda hand picked depending on size of large rock.
the pre-ground big rock is usually done in 2 weeks
the smaller rocks are run again with the next big rock since they are not pre-ground.
this time I will run 5 of these small 6" PVC barrels(6 pound capacity). So 5 big rocks.
Will do grit additions very 1-2 days, do a 5 barrel mass clean out after 7-10 days. Yes, clay thickener and 80% barrel fill.
at clean out I just pour all the barrels into one tub and mix the whole mess.
then put one big rock in each barrel and fill in as needed from the pile of small rocks, charge, and run again.
add more small rocks as needed in the last barrel(the new tumble barrel) and record barrel number
meantime I will per-grind another 5 big rocks and keep using the same small tumbles, over and over.
after 2 big rocks the small tumbles are way reduced, try to keep them together as new small tumbles are added into numbered barrels
barrels are numbered in roman numerals, cut in the barrels with an angle grinder so easily visible
At 2nd and 3rd(3rd if necessary)clean outs I use two tubs to dump in, the barrels with newer small rocks and those with older small rocks.
Basically the small rocks separated as if early crop and older crop(grower's terms)
Got no inhibitions about grinding more big rocks. That grinding wheel on the 3600 RPM tile saw is calling me. Love that thing on the tile saw. Wish it had a wider face...
May cut the tile saw table so I can have better access to the blade.
Process seems complicated but it is not. I did it with 3 big rocks/ 3 barrels before. This time 5 barrels. It is easy tumbling. The small normal tumbles get ground fast.
Then the bonus of the big rocks about every two weeks. So early pay off in spitting out the pre-ground big rocks.
Just keep in mind I use a big vibe to do the finish work one big rock at a time in vibe -or- use dividers in the vibe and do 2 or 3 big rocks at a time in the vibe.
The vibe mouth is 4 inches too, so the 4 inch big rocks work for it.
The rotary is 100% SiC 30 grit with clay.
Here is a typical mix for two 6 pound barrels running two big rocks. You can see ratio of smalls. Stainless pan has 1/4" holes for size reference.
The small rocks become by-products in a sense. I get into the big rocks. This mix is a very gentle run, smalls on the small side, but so gentle. PVC tells, it's loud.
And the smalls were smaller because I was running these 2 barrels at 55 RPM @ 85% fill. Need 85% fill at 55 RPM. My little barrels have an 80% line inside the barrels for measurement. Easy.
Easy and fast and accurate to load at 85%.
some very thin chips in this load, no broken chips. Gentle at 85% fill and fast 55 RPM with clay slurry: