jamesp
Cave Dweller
Member since October 2012
Posts: 36,562
|
Post by jamesp on Apr 28, 2015 5:47:14 GMT -5
Tumbling dallasite, granite, pink felspar, amazonite, labrodolite, impactite, rhyolite together. Have used a heavy clay slurry the whole way. Granite a problem. Under cut at SiC 30/60 step. Under cut at SiC 220 and garnet 300. ran these two steps for a long time. Under cutting worse in these two steps. Everything looks great except the granite. Looks like the felspar/quartz contact areas pitted, and the mica got dug out. This granite saws and finishes on a wheel just fine, no pits whatsoever. Tumbling process finds the soft and weak spots and chips/gouges/abrades them out. Thought about mixing some portland cement with garnet 300 abrasive and making a grout to seal pits... Re run with 220. Whole batch wet
|
|
chassroc
Cave Dweller
Rocks are abundant when you have rocktumblinghobby pals
Member since January 2005
Posts: 3,586
|
Post by chassroc on Apr 28, 2015 7:39:06 GMT -5
I once traded a FRB of agate/PW for someones granite. Big pieces that filled a FRB.
I had similar results.. Some tumbles fine like the pink in the lower right corner of your bottom photo
and some does not...I decided to cut my losses and use it as garden pavers instead
CHARLIE
|
|
panamark
fully equipped rock polisher
Member since September 2012
Posts: 1,343
|
Post by panamark on Apr 28, 2015 8:39:35 GMT -5
jamesp James, I think you are correct in that "Tumbling process finds the soft and weak spots and chips/gouges/abrades them out." Like Charlie says, some granite seems to be tight, and some is very granular. The tumbling pounding loosens and removes some of the poorly cemented grains making the outcome a rough surface. Strange because when you cut it can seem so smooth out of the saw, but tumbling subjects it to much pounding at various angles. Too bad, as some of the gorgeous granites are too grainy for tumbling. Maybe James you will figure this mystery out too.
|
|
Deleted
Deleted Member
Member since January 1970
Posts: 0
|
Post by Deleted on Apr 28, 2015 9:23:50 GMT -5
Put one piece of granite and some grit in a tennis ball and seal it. Add to tumbler. Results may vary because i do not know if it has been done before. hahaha Jim
|
|
|
Post by captbob on Apr 28, 2015 9:25:04 GMT -5
I agree with Mark's agreeing with you in that "Tumbling process finds the soft and weak spots and chips/gouges/abrades them out." Pretty much seems to be what happened here. Wouldn't call this undercutting. I consider this undercutting. A softer material is removed at a faster rate than the harder material.
|
|
Fossilman
Cave Dweller
Member since January 2009
Posts: 20,711
|
Post by Fossilman on Apr 28, 2015 9:33:05 GMT -5
I have only tumbles a few pieces of granite,it was from Alaska....Smaller than my thumb-it tumbled great with my agates and petwood.... I have trouble with some jaspers myself.... Hope you get this problem figured out James...
|
|
jamesp
Cave Dweller
Member since October 2012
Posts: 36,562
|
Post by jamesp on Apr 28, 2015 10:13:32 GMT -5
Yep, agreed- under cutting is captbob situation above. Perfect example Bob. panamark described the granite situation-"The tumbling pounding loosens and removes some of the poorly cemented grains making the outcome a rough surface". captbob's jaspelite ?? is more desirable(to me) than the chunks being hammered and abraded out of the granite. Granite fine when sawn and wheel worked. Shame it tumbles crappy, it is attractive. I thought the super thick slurry may prevent the grain removal. Oh well, they will make great window polished morsels.
|
|
jamesp
Cave Dweller
Member since October 2012
Posts: 36,562
|
Post by jamesp on Apr 28, 2015 10:27:52 GMT -5
I once traded a FRB of agate/PW for someones granite. Big pieces that filled a FRB. I had similar results.. Some tumbles fine like the pink in the lower right corner of your bottom photo and some does not...I decided to cut my losses and use it as garden pavers instead CHARLIE Yep, sure makes cool countertops, again, it wheel finishes just fine. Another railroad track has a tight grained granite quartzite. It will tumble. And the colors and patterns are well worth it. But no pretty felspar patches in it. Looking forward to windowing some of these Charlie. So not all for naught. Too proud of my Georgia granite to put it out to pasture just yet. Window machine 100 200 400 left to right on front, 800 1500 3000 right to left on back side. Maybe 3 minutes per stone, and soaks operator.
|
|
|
Post by Jugglerguy on Apr 28, 2015 14:51:27 GMT -5
Charlie, I you ever want to trade granite for agates again, let me know! I can pick up lots of nice granite, but agates are very scarce.
|
|
|
Post by Toad on Apr 28, 2015 15:29:01 GMT -5
I only use granite for filler. Occasionally one would make it through the process, but super rare...
|
|
jamesp
Cave Dweller
Member since October 2012
Posts: 36,562
|
Post by jamesp on Apr 28, 2015 15:50:58 GMT -5
I only use granite for filler. Occasionally one would make it through the process, but super rare... Some granites are tight grained. Make great tumbles.
|
|
|
Post by Toad on Apr 28, 2015 22:48:58 GMT -5
I never ran across the tight grained ones...
|
|
jamesp
Cave Dweller
Member since October 2012
Posts: 36,562
|
Post by jamesp on Apr 29, 2015 4:03:36 GMT -5
I never ran across the tight grained ones... It is more like quartzite, but has felspar and mica. High quartz content. Fine grained
|
|
|
Post by Toad on Apr 29, 2015 12:40:19 GMT -5
Nice, I'd like to run across that!
|
|
jamesp
Cave Dweller
Member since October 2012
Posts: 36,562
|
Post by jamesp on Apr 29, 2015 17:23:19 GMT -5
Nice, I'd like to run across that! You would be amused, it is collected out of railroad gravel. The railroads down here spec out hard gravel. Smaller felspar sections, higher quartz content. No photos of the dense railroad stuff yet. Still rounding a batch up from various tracks, gathering variety. Strange granites, no telling where a rail goes. So the source would be hard to ID. It is mixed with many granites from older additions. Some with lots of white granite, but maybe 5% is veins that were in it. Some freckled with garnets or cool mica crystals.
|
|
Deleted
Deleted Member
Member since January 1970
Posts: 0
|
Post by Deleted on May 2, 2015 13:29:07 GMT -5
I sure hope you do not make a train fall over. The rail road people frown upon trains falling over. Around here they will come at you like a locomotive if they catch you removing anything from the rail road right-of- way. Even the glass insulators off of a line of poles that hasn't been used for fifty years and the wires have fallen down. Jim
|
|
stonemaster499
noticing nice landscape pebbles
Member since July 2014
Posts: 97
|
Post by stonemaster499 on May 3, 2015 23:15:43 GMT -5
jamesp try tumbling the granite assuming the softer stone is the target material, and not vice-versa. This way, the undercutting is reduced. also try to minimize the tumbling times to reduce the undercutting even further. For me, worst at 500-1000 stages.
|
|
jamesp
Cave Dweller
Member since October 2012
Posts: 36,562
|
Post by jamesp on May 5, 2015 6:23:54 GMT -5
I sure hope you do not make a train fall over. The rail road people frown upon trains falling over. Around here they will come at you like a locomotive if they catch you removing anything from the rail road right-of- way. Even the glass insulators off of a line of poles that hasn't been used for fifty years and the wires have fallen down. Jim LOL. I pick my spots Jim. Or used to. The other day the city police asked me what I was doing. Rock collecting, he just nodded his head and drove off. Betting the train detective would not be so unconcerned.
|
|
jamesp
Cave Dweller
Member since October 2012
Posts: 36,562
|
Post by jamesp on May 5, 2015 6:33:48 GMT -5
jamesp try tumbling the granite assuming the softer stone is the target material, and not vice-versa. This way, the undercutting is reduced. also try to minimize the tumbling times to reduce the undercutting even further. For me, worst at 500-1000 stages. The best the granite looked was in the coarse grind Robert. After that it was down hill. I would have thought that SiC 220 would have smoothed them, put it gouged out the soft spots. The longer it ran in 220 the worst it got. I see what you are saying about minimizing. Run each grit only long enough to get a surface finish that the next step will remove ?? I can window the granite on the diamond wheels and it looks like plate glass. no pits at all.
|
|
stonemaster499
noticing nice landscape pebbles
Member since July 2014
Posts: 97
|
Post by stonemaster499 on May 5, 2015 13:48:28 GMT -5
jamesp try tumbling the granite assuming the softer stone is the target material, and not vice-versa. This way, the undercutting is reduced. also try to minimize the tumbling times to reduce the undercutting even further. For me, worst at 500-1000 stages. The best the granite looked was in the coarse grind Robert. After that it was down hill. I would have thought that SiC 220 would have smoothed them, put it gouged out the soft spots. The longer it ran in 220 the worst it got. I see what you are saying about minimizing. Run each grit only long enough to get a surface finish that the next step will remove ?? I can window the granite on the diamond wheels and it looks like plate glass. no pits at all. Exactly. "Run each grit only long enough to get a surface finish that the next step will remove " James, I was hoping you would figure this out, before i did ! So, haven't had time to figure out the solution, just mastered how to create the problem In our amazonite, the white [chalk/ calcium carbonate (h.3) ]** assumption that it is CC... chalk is fine until 1000 stage. The amazonite has black quartz, tourmaline, topaz and chalk - all minorities in the stone. When tumbling, I target H. 6.7, which gets good results. However, the undercutting of the CC is a bit of an issue and the longer in, the worse. Same with labradorite and mica/ Septarian had the same issue with the fossilized sedimentary mud. Using a granite polish line (granite slabs 5 feet x 9 ft = 45ft2 per slab, you need to make special adjustments for pressure and hardness to get good results. So this is not done "by hand", but not banging around in a tumbler either. When you get good results by hand, IMO, it is because you are using varying pressure, as needed, where needed. (ie if an area needs more you give it more). I HOPE OTHER MEMBERS HERE CAN help us solve this problem! Other ideas on my TODO list following the fastest time to get the job done theory in order to minimize the undercutting: a) skipping 1000, and going to 5-7 micron Al Oxide evaluate undercutting, before moving onto <2 micron AL Ox polish b) same as above, but use submicron rather than <2micron c)try 500Al Ox for 4 days rather than 1-2, and skip 1000 to polish. d) 500 SiC--->500 Al Oxide, and skip 1000 Al Ox. to 5-7 micron polish. evaluate undercutting.
|
|