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Post by tims on Jun 9, 2016 20:07:02 GMT -5
I didn't want to hijack another thread with a myriad of questions, so here goes.
I put about 90 minutes into a slab with minor saw marks and can't see a lot of progress yet. It is slightly less dull than the unpolished side of the cut. I'm using 80 grit on glass with a 2.5"x4" slab of Teepee-ish agate.
Questions:
Is 80 grit too fine to start with? I've only got 80, 220 and 400 on hand.
How wet should the grit be? When I first wet the grit the rock glides easily, but i'm not sure if that's a good or bad thing. As the slurry dries it gets noticeably more difficult to move the rock around but in my mind I associate more resistance with better polishing action.
How durable is the grit? Should I be swapping out to fresh grit every few hours, or is it ok to keep using it even for multiple rocks? Any guestimate?
Can I let the grit dry and then add water later and use it again?
Does the grit need to be washed off after polishing, or is it just polishing compound that turns into cement if you let it dry on?
And lastly, why is my left hand so stupid?
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Post by spiceman on Jun 9, 2016 22:06:16 GMT -5
In reference to the last question... ( because my left side is bad too and my therapist said that I need to use it more,make yourself. I'm sure you knew that. I use the grit from the different stages in tumbling the same as the hand lapping. .
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Post by Deleted on Jun 9, 2016 23:36:51 GMT -5
Grit should be consumed. It should be replinished until that stage is complete.
80 grit is a good start.
When im cutting spheres or flat lapping with grit, i notice too wet is a waste and the cutting happens as it dries out. If it gets too dry the cutting stops again as the slurry innaoropriatelt protects the grit.
Wet/dry cycles may work. Unless it doesnt.
Clean well between all stages and after polish.
Stupid left arm?
Hmmm.......
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jamesp
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Post by jamesp on Jun 10, 2016 6:08:04 GMT -5
These 50 grit diamond pads should last about 50 years hand grinding and sure cut fast. They seem to have very sharp diamonds unlike diamond segments, they cut quick. Must be cracked diamonds instead of dull crystals requiring less pressure. By a set 50-100-200-400-800-1500 to get to polish. 5 inch probably better than 4 inch. Maybe that depends on your range of motion. Or you could just try a 50 grit pad for coarse to try for coarse. I think you would be pleasantly surprised. www.mcgillswarehouse.com/dpp126-5in-50-grit-diamond-pad-for-wet-polishing
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Post by tims on Jun 10, 2016 18:37:39 GMT -5
Lots of good info there, thanks Shotgunner. Just what I was needing to know.
Jamesp thanks a million for the link, I've looked and looked for someplace in the US to find similar pads. I'm going to order a 50 and 100 to start and see how grit works from there, but may well end up getting the full set down the line.
Awesome. Thanks guys.
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jamesp
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Post by jamesp on Jun 11, 2016 2:20:03 GMT -5
Those pads wear fast on concrete that sheds silica sand. Like wet concrete. On agates, hard concrete, granite, they last forever, even at 3600 RPM. Some of the sharpest abrasive I have ever seen is embedded in that rubber. And diamond, so it is totally hard. I have an 18 inch saw. Adjusted it to cut with out saw marks best I could. Cut rock slow. Face of cut was darn near 400 finish. It took about 10 minutes to get a face polish starting at 400, then 800-1500 on a 3" X 5" face. at 3600RPM. The face plate for the 3000 pad was warped and caused the rock to bounce making the 3000 pad useless. Smaller 1-2 inch sawn rocks were done fast. 60 seconds each, 200-400-800-1500 and could do the 3000 with smalls. Those pads come in 10,000. Never tried them Please feedback experience with 50 pad vs 80 SiC. Guessing you will feel the grinding action on the 50 pad. Putting the rock against a 100 pad at 3600 RPM vs a 1500 pad at 3600 RPM is night and day. The 100 pad tugs on the rock, muddies the water. Cutting fast. 1500 pad eerie, no friction whatsoever. I wish they would supply the pad without velcro so that it could be glued(epoxy) very flat to face plate. I wish I used 5 inch pads instead of 4 inch. If they ever come out with affordable 8 inch pads they would revolutionize lapping. And a precision aligned face plate unlike my welded 4 inch washer face plates. I mounted the faceplates on the grinder and turned them on whilst holding a grinder to the face to 'lathe' them flat. That helped, but not perfect. 100 pad, rarely used. Leaves deep scratches at 3600 RPM. Faceplate a bit crooked causing bounce also. 200 pad used heavily. It grabs. Had a crash or two removing saw marks on large rocks. 400 pad used very much. Does not grab like the 200 pad. And does not remove saw marks. Too fine. My coral halves collection. Most are faced polished w/these pads. Used to sell them to interior decorators on mounts or in lamps.
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Post by Jugglerguy on Jun 11, 2016 7:57:38 GMT -5
I love your coral display, James!
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Post by MrP on Jun 11, 2016 8:05:09 GMT -5
My coral halves collection. Most are faced polished w/these pads. Used to sell them to interior decorators on mounts or in lamps. jamesp My wife thinks that is one great room. We love the industrial look of it!.............................MrP
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jamesp
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Post by jamesp on Jun 11, 2016 9:07:53 GMT -5
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Post by Deleted on Jun 11, 2016 9:30:43 GMT -5
They have 7"...
Hmmm.....
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Post by tims on Jun 11, 2016 14:35:57 GMT -5
Wow James your studio is incredible. Loving the coral displays. Someone from McGill's called me this morning asking about my order. What will I use the pads for? What kind of equipment do I use? What materials do I work on? (But aren't agates round?) They seem very interested in providing customers with exactly the products they need. I wish they would supply the pad without velcro so that it could be glued(epoxy) very flat to face plate. If they ever come out with affordable 8 inch pads they would revolutionize lapping. And a precision aligned face plate unlike my welded 4 inch washer face plates. It might be worth contacting them with your suggestions. Let them know there is a legitimate market for a new product and maybe they'd manufacture it.
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jamesp
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Post by jamesp on Jun 11, 2016 15:47:12 GMT -5
Wow James your studio is incredible. Loving the coral displays. Someone from McGill's called me this morning asking about my order. What will I use the pads for? What kind of equipment do I use? What materials do I work on? (But aren't agates round?) They seem very interested in providing customers with exactly the products they need. I wish they would supply the pad without velcro so that it could be glued(epoxy) very flat to face plate. If they ever come out with affordable 8 inch pads they would revolutionize lapping. And a precision aligned face plate unlike my welded 4 inch washer face plates. It might be worth contacting them with your suggestions. Let them know there is a legitimate market for a new product and maybe they'd manufacture it. They used to sell a LFRB full of 1 inch marbles for $50. Me and my neighbor bought one and sling shot them over the trees back and forth at each other. Marbles all over the hood/garden lol. No one struck yet. I just took a 60 grit grinder and carefully ground off the velcro backing. No problem. McGill's a bang up operation. I think they have the biggest(glass) marble biz in the world. And a peculiar assortment of products. Just a big import warehouse.
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jamesp
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Post by jamesp on Jun 11, 2016 15:50:53 GMT -5
Scott, I think I saw a lapidary lap that used those 7 inch pads. That would be the ultimate lapper. As long as you feed water and keep RPM down those pads last forever on mohs 6-7. I could see them stepping up to 9 inch pads. Another standard angle grinder size for the hale and hearty.
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jamesp
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Post by jamesp on Jun 11, 2016 15:53:16 GMT -5
I love your coral display, James! Thanks Rob. Welded those shelf supports up in a jiffy. Cutting and painting the boards took the time.
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Post by Deleted on Jun 11, 2016 18:32:03 GMT -5
I love your coral display, James! Thanks Rob. Welded those shelf supports up in a jiffy. Cutting and painting the boards took the time. That the trouble im having with my tumbler. Painting! Lol
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jamesp
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Post by jamesp on Jun 11, 2016 19:27:13 GMT -5
Thanks Rob. Welded those shelf supports up in a jiffy. Cutting and painting the boards took the time. That the trouble im having with my tumbler. Painting! Lol I must be messy. I would feel like I was painting the inside of a trash can. Dirtier process than muddy aquatic plants.
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Post by Deleted on Jun 11, 2016 19:38:59 GMT -5
Its just lumber, but shiznitt, i suck at painting!
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jamesp
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Post by jamesp on Jun 11, 2016 19:55:40 GMT -5
Its just lumber, but shiznitt, i suck at painting! Natural rust patina on steel suits me. Despise painting.
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Post by tims on Jun 30, 2016 3:38:13 GMT -5
These 50 grit diamond pads should last about 50 years hand grinding and sure cut fast. They seem to have very sharp diamonds unlike diamond segments, they cut quick. Must be cracked diamonds instead of dull crystals requiring less pressure. By a set 50-100-200-400-800-1500 to get to polish. 5 inch probably better than 4 inch. Maybe that depends on your range of motion. Or you could just try a 50 grit pad for coarse to try for coarse. I think you would be pleasantly surprised. www.mcgillswarehouse.com/dpp126-5in-50-grit-diamond-pad-for-wet-polishingOK, been at this for a few weeks whenever i need some zen time. I'd started the slab with 80 tumbling grit trying to knock down a fingernail-depth saw mark. After 2+ hours it was only slightly smoother (if at all), my arm hurt, and i was losing hope for hand polishing. When my 5" 50 and 100 pads showed up i gave it another go, and after ~90 minutes with the 50 i had the slab smooth to the touch and free of saw marks. Gave it about an hour on the 100 pad, then an hour with 220 grit, and today an hour with 400 grit. It's not a shiny polish yet by any means but the colors and banding are starting to show better. I ordered some aluminum oxide polish and am debating going from 400 to polish, but i should probably get another intermediate step of 800-1000 in first (correct?). Anyway, the finer grits seem to work better than the course 80 grit did. I'm wondering if maybe a cast iron sheet rather than glass might work better for course grit to hold it in place rather than having it slide around, but since i've got the pads now i have no reason to test it. I'd like to test a 200 / 400 pad vs. the grit to see if they'd be as huge an improvement as the course pads, but since i'm cheap and i have lots of grit on hand that will probably wait. The 400 grit today was interesting; it was 90ish outside so my slurry would go from wet to dry every few minutes, and i could feel the resistance build as if the rock was magnetizing to the glass. After a couple cycles it started getting difficult to pull the slab off the glass in order to spray it with water, and after 30 minutes or so i could easily lift the 2.5 pound glass plate by lifting up on the slab. I'll get a comparison pic of the polished heel slab vs. the unpolished cut when i get to a fair polish ... Haven't been getting any pics during the process but if it works out well i'll try to get some visual documentation on the next piece. Maybe a 4 hour montage video that i'll post to youtube at normal speed as ASMR or something It is kind of soothing and puts my cat to sleep. Oh yeah another thing i'd highly recommend to anyone using the 5" pads is a palm sander. I got a nice ergonomic foam one from amazon for ~$15 and it was worth every penny: Hand Sanding Kit
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jamesp
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Post by jamesp on Jun 30, 2016 4:13:34 GMT -5
timsThose pads are nothing but fresh sharp diamonds for 5mm. Compare Knoop hardness for diamond: Diamond-7000 SiC-2460 Alum Ox-2100 So the diamond is hardly going to wear. Basically an infinite supply of super sharp super tough cutting abrasive. The other abrasives are no comparison. Crushed diamond is as good as it gets. They are designed to quickly take large areas of saw cut quartz bearing granite from rough to polish finish at a production rate. They do it in steps 50-100-200-400-800-1500-3000. No short cuts, fastest path to polish is using each of those pads. Increments designed to get from point A to point B. The softest of quartz gems is crystalline quartz @ knoop 820, the hardest is garnet @ knoops 1340 for example After the 3000(or maybe a 10,000) pad you should go with a wet lap of AO 14,000. The pads on the 3600 RPM grinder show little effect of wear. And have many hours on them. In a hand finish application they should last longer than you and I doing consecutive life terms. You may want to order some 4 inch pads 200 to 3000 just to try.
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