jamesp
Cave Dweller
Member since October 2012
Posts: 36,159
|
Post by jamesp on Jan 24, 2015 2:41:02 GMT -5
Looking at the list of grits to hand polish a telescope mirror to optical grade polish. 10 steps of abrasive. Hand polishing inefficient and slow. Some do mirrors with 5 steps of abrasives. Note polish is cerium oxide. A tumbler is a much more efficient grinding machine, so less steps required. - One 8 inch Telescope Mirror Blank (Supremax® 33) - 1 lb Gugolz Pitch (Please choose type above - Picture shows 2 lb container) - 1 lb Silicon Carbide #60 - 3/4 lb Silicon Carbide #80 - 1/2 lb Silicon Carbide #120 - 1/2 lb Silicon Carbide #220 - 1/4 lb Silicon Carbide #320 - 1/4 lb White Aluminum Oxide 25 Micron - 1/4 lb White Aluminum Oxide 15 Micron - 1/4 lb White Aluminum Oxide 9 Micron - 1/4 lb White Aluminum Oxide 5 Micron - 1/4 lb Cerium Oxide Polish Judging surface finish: Sample Plates: If you are having trouble judging pit sizes, make up some sample plates. Using scrap window glass cut into small squares, or microscope slides, grind your sample plate with a single known grit and then label it. Your sample plates will have only pits of the given grit size, and you can use them as a reference when examining your mirror (which will possibly have two or more pit sizes present). This has helped a number of students in the Stellafane mirror class gain confidence in judging pit sizes; the author uses the set shown below, neatly mounted, for use in class (yours can be loose, and labeled with a pencil on one edge). (Note grit and micron conversions do not compare with other charts.ha) More stellafane.org/tm/atm/grind/fine.html
|
|
|
Post by Starguy on Jan 24, 2015 11:35:12 GMT -5
jamespGarnets aren't really too hard to tumble. I don't think they take longer than anything else. As with everything, it takes a while to get them through the coarse grit. The hardest part is to get enough good material because the don't polish well if they're in with agates. Later Brent
|
|
|
Post by captbob on Jan 24, 2015 11:52:26 GMT -5
Just spent the morning doing barrel clean-outs*, and the obsidian batch finally moved on to 320 after three weeks in 120/220. Granted, the 60/90 took Three Months, but I started out with some pretty rough rock. Figure each step left (500/1000/polish) will take two weeks - polish may go longer, we'll see.
I couldn't find a bruise anywhere, even using a magnifying glass. Plenty of filler used - ceramics and plastic pellets. Started to include plastic pellets in 120/220. VERY full barrel & lots of water. Which, may cause longer run times, but it's an extremely cushioned load.
Fingers crossed. I just want it done!
*before the coming cold front takes the daily highs down into the lower 60s for the next week!
|
|
jamesp
Cave Dweller
Member since October 2012
Posts: 36,159
|
Post by jamesp on Jan 24, 2015 15:57:50 GMT -5
jamespGarnets aren't really too hard to tumble. I don't think they take longer than anything else. As with everything, it takes a while to get them through the coarse grit. The hardest part is to get enough good material because the don't polish well if they're in with agates. Later Brent Thanks Brent. I have tumbled our crappy grainy Georgia garnets, but never those hard glassy Idaho garnets. It probably helps that they are somewhat round to start with.
|
|
jamesp
Cave Dweller
Member since October 2012
Posts: 36,159
|
Post by jamesp on Jan 24, 2015 16:08:35 GMT -5
Just spent the morning doing barrel clean-outs*, and the obsidian batch finally moved on to 320 after three weeks in 120/220. Granted, the 60/90 took Three Months, but I started out with some pretty rough rock. Figure each step left (500/1000/polish) will take two weeks - polish may go longer, we'll see. I couldn't find a bruise anywhere, even using a magnifying glass. Plenty of filler used - ceramics and plastic pellets. Started to include plastic pellets in 120/220. VERY full barrel & lots of water. Which, may cause longer run times, but it's an extremely cushioned load. Fingers crossed. I just want it done! *before the coming cold front takes the daily highs down into the lower 60s for the next week! Crossing my fingers for you too. you gotta get er done w/a rotary. You will be my hero; I know that would make your day. Cushion, fillers, fuller barrel-sounds like a recipe. As far as your 60F problem, well, let's hope a hurricane brings in warmer weather at 150 MPH. I am pumped, yesterday did 3 hours 500, 5 hours 1000, 6 hours 5000. Just started 14,000 one hour ago. All in the vibe with sugar. Pulled a 1 hour sample from 14,000 and it looks promising. 2-4 more hours and I will know if I get a polish.
|
|
|
Post by captbob on Jan 24, 2015 16:24:01 GMT -5
I'll get er done, just taking much longer than I care to spend on such a boring looking rock.
Do you shut the vibe down at night? If so, what do you do with the load?
|
|
jamesp
Cave Dweller
Member since October 2012
Posts: 36,159
|
Post by jamesp on Jan 24, 2015 16:41:05 GMT -5
I'll get er done, just taking much longer than I care to spend on such a boring looking rock. Do you shut the vibe down at night? If so, what do you do with the load? In this case I did because I am experimenting w/shortest possible run times. Polish was the next step at 9PM last night. I wanted to watch the polish step closely, so I waited till today to run it. So last night I added dish soap to the load and vibed it in for a couple of minutes and then filled the hopper with water and turned it off for an easy clean-out today. Normally I leave it run 24 a day. Learn on those boring ones and next time hit the fancy obsidians. I am running breccia brown, breccia mahogany, breccia gray, double flow, silver sheen, mahogany sheen, a silver sparkle type, a silver and black banded and several others. Quite a mix, and don't know what they are supposed to be called.
|
|