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Post by Condor on May 1, 2007 7:56:32 GMT -5
To those of you who pre-grind your rocks for tumbling...How do you do it so that they come out with that nice round shape such as you would get if you bought them commercially? I know you can leave them in first stage for a long period of time, and that will work, but I think pre-grinding them will also help.
Condor
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stefan
Cave Dweller 
Member since January 2005
Posts: 14,113
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Post by stefan on May 1, 2007 8:37:57 GMT -5
Are you thinking like a tumbled cab? or just nicely shaped nuggets?? I pregrind some stuff (actually failed cabs) on the 100 belt- then toss it into 120/220-
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lsmike
spending too much on rocks
Maxwell's demon lowers tumbling entropy
Member since January 2007
Posts: 468
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Post by lsmike on May 1, 2007 8:50:42 GMT -5
Condor:My Lakers are usually nodular to begin with,but if I want them rounder I work them on the coarse wheel by turning them in a random motion.This is similar to what a non-lap type sphere machine does.I also hit the higher areas longer.It might also help to saw off some high areas first.Mike.
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RockyBlue
fully equipped rock polisher
Go U.K.
Member since June 2006
Posts: 1,719
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Post by RockyBlue on May 1, 2007 11:15:49 GMT -5
Hey Condor!
For tumbling i use a 100 grit green wheel on my grinder and if its real good matieral i use my Dremel with a green stone to round out the pits,hope this helps.....................Rocky
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lastl98
spending too much on rocks
Member since February 2007
Posts: 410
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Post by lastl98 on May 1, 2007 12:06:44 GMT -5
I've got a pile of some Bots that I'm going to try either grinding them on my diamond wheel or cutting & shaping on my trim saw. I did throw a small batch in my 3lb. tumbler with some very coarse 40/70 grit that I just got from the Shack. I'm hoping the coarser grit will keep me from having to do too much shaping/grinding/cutting to get the results we all seek here! Last  |
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RockyBlue
fully equipped rock polisher
Go U.K.
Member since June 2006
Posts: 1,719
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Post by RockyBlue on May 1, 2007 14:03:24 GMT -5
Hey Last!
I think bots are the best looking stones,but it takes a very long time,don`t rush it or you will end up with a medium looking batch like i did and mine was in 60/90 for 4 mo. I think there`s a thread
way back of some that Don did and they are AAA in my book,what a shine,you might ask Don for his reciepe.................Rocky
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Post by akansan on May 1, 2007 14:05:41 GMT -5
I've preground a few stones on the WF - basically cutting into a rectangular shape and then smoothing the edges. I'll let them run in the rotary for another two weeks to finish rounding the cut edges, but they turn out pretty nicely.
It's not a quick process though. It takes me about 30 minutes on the WF to get one stone in the general shape I'm wanting it. My original thought was to start this way to really cut down on tumbling time, but it took me so long to do them, they would have been in the tumbler a week or two already by the time I finished one barrel full of stones.
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Post by stoner on May 1, 2007 14:42:21 GMT -5
Hey Gil, what everyone said is just about what needs to be done. For the least amount of tumbler time I think Ronda has the right idea but 30 minutes on one stone is way too long. Seems like you could cut some 1" thick slabs, hotmelt glue 2 of them together(or more if you have a larger saw) then cut the slabs into cubes and just throw them into the tumbler. It may still take a while but the shapes would be better than just waiting for rough stones to get to that point. If you want to grind the corners I'd suggest getting a coarser wheel, like a 30 or 50g.
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Post by larrywyland3 on May 1, 2007 18:34:00 GMT -5
I have been experimenting with this idea and checking out what everyone has done. So far, I have tried a 60 grit wheel on my cabbing machine to shape and round down the edges. I left the center flat to save time and hoped the tumbler would finish the job for me. I did each stage for a week and they came out pretty good. I still had a flat spot in the center. If I left them in the coarse grind longer it may have rounded out the center. I have some cross in polish right now; so far none have broke. I put in a lot of plastic pelets with this batch to see how that shapes things up. So far the plastic pelets seem to slow the rounding in the coarse batch, but they get into every little spot and the crosses are coming along nicely. My guess is that to the trained eye a tumbled cab will have some tells on it that letting you know it was tumbled. My first batch was still real nice. I drilled some for pendants and they look great.
When I find my camera I will put up some pictures.
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Post by cpdad on May 1, 2007 19:51:17 GMT -5
i pre grind just about everything...i do it all on a 100 grit silicone cardide wheel on a regular 3600 rpm bench frinder...and all by hand...i take a handful to work...and at lunch or when i have a few minutes...i grind away i can do a handful in 30 minutes. all of the pendants i sell are cut on the workforce...ground on the 100 grit silicon carbide wheel...and go straight to 220/120...i have some so called cabs that are domed completly....but it does take a steady hand to get a domed peice...is domed a word ;D. here is a pic of preground massive quartz...and 1 of my so called domed cabs...the cab is jamies material....all 1 week stages except polish...10 days for that....and of course pics suck...but an idea can be had i suppose...kev. click  |
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Post by Bikerrandy on May 1, 2007 20:57:55 GMT -5
I pre-grind everything. I use a mixture of cutting and grinding. I first cut the desired shape, then I gring the edges round with a regular bench grind, lapidary green grit wheel (silicon carbide, 100 grit) installed, and a shop-vac hooked up to the back of the grinding wheel casing for dust control. (I grind right in front of my 1930 Chevy, no dust! )
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