betho
off to a rocking start
Member since June 2021
Posts: 2
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Post by betho on Jun 19, 2021 21:56:42 GMT -5
Hi! I got my first lapidary machine this past Christmas - an 8" Hi-Tech slant cabber. I have been mainly using it to shape and polish agates, amethysts and chalcedony pieces I collected (Thunder Bay is a super fun area to explore). Right now I am trying to polish some flat sliced agate pieces. But I have cloudy spots that won't polish, I think they may be low spots. Doesn't seem to matter how long I keep a piece at a 180 grinding plate I can't get rid of the low spot. Do I need new plates? A more aggressive grinding plate? More patience? I have never replaced grinding plates or polishing discs before so don't really know when I should. The other option is to save up for a vibe tumbler and stick the agate slices in there.
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Post by Pat on Jun 19, 2021 22:14:15 GMT -5
Welcome from California, and good luck. Lots of experts here; not me.
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Post by Rockoonz on Jun 20, 2021 9:42:13 GMT -5
I'm not a fan of HiTech but their slant cabber is probably the best they sell. It sounds like you're polishing flats, which indeed requires patience and a lot of time. I would get an assortment of very coarse discs, like 60/80/100 to rough out your flats before going to 180. The reason for the assortment is that some materials can begin to chip if too coarse and that way you can find the right one for the material at hand. When doing flats you can start by moving your piece around on the disc for even wearing of the disc, but at some point you want to hold it in one place and finish it, because moving it will tip it and not grind the entire surface perfectly flat.
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stonemon
Cave Dweller
Member since January 2017
Posts: 1,024
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Post by stonemon on Jun 20, 2021 9:50:27 GMT -5
Welcome to the forum!
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hummingbirdstones2
fully equipped rock polisher
Vince A., 1958-2023
Member since August 2018
Posts: 1,461
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Post by hummingbirdstones2 on Jun 20, 2021 11:35:18 GMT -5
If the dull spots are all in the centers of the faces you might have to give the pieces a slight dome.Just enough to let your finer grits do their job.
If you want perfectly flat surfaces it takes more time. To that point, if you were getting good results in the past using the same techniques, you might be right about needing some new laps.
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Post by rmf on Jun 20, 2021 13:17:14 GMT -5
It may be that the spots are a different crystal which may be softer and undercut. That means you will never get to the bottom. This would be like small quartz crystals in an Agate matrix. They polish differently but they should polish.
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betho
off to a rocking start
Member since June 2021
Posts: 2
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Post by betho on Jun 20, 2021 18:31:14 GMT -5
Thanks all! Sounds like courser grit discs and probably fresh polishing pads for me!
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