yetiabitibi
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Member since February 2016
Posts: 25
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Post by yetiabitibi on Feb 19, 2016 9:16:18 GMT -5
Hi all, I'm new to the forum and, somewhat, to lapidary.
I'm starting to do some polishing with a 16" Covington vibrolap and I was wondering how often do you change the grit? I'm doing batches right now, passing a large quantity of slabs at the same grit before going to the next stage. I usually run the vibrolap 4 hours at a time, but how often do I need to replace/refresh the grit?
Thanks for any help.
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Deleted
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Post by Deleted on Feb 19, 2016 11:07:02 GMT -5
I polished some stuff last tuesday night. I added grit when the grit was no longer there. You can feel the cutting action of the grit. When that stops add more.
Keep the water to just enough to thin the mud. Too dry and the mud encases the grit not allowing it to work and too wet washes away good grit.
Me and an 11 year old polsihed a couple geodes in 45 minutes from cut to polish.
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Deleted
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Post by Deleted on Feb 19, 2016 11:10:50 GMT -5
I polished some stuff last tuesday night. I added grit when the grit was no longer there. You can feel the cutting action of the grit. When that stops add more.
Keep the water to just enough to thin the mud. Too dry and the mud encases the grit not allowing it to work and too wet washes away good grit.
Me and an 11 year old polsihed a couple geodes in 45 minutes from cut to polish.
How long in a temporal perspective is dependent on many factors. Rough takes the longest and that will take longer depending on the saw cut. 200 is faster. 500 faster yet and 800-1200 go pretty quick.
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yetiabitibi
starting to shine!
Member since February 2016
Posts: 25
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Post by yetiabitibi on Feb 20, 2016 15:43:15 GMT -5
Thanks for the reply. For the moment I'm just adding 1 tbsp of grit after every 4 hour run. They're taking a long time because it's pretty hard material (agate and fossilized wood mostly) and the cuts weren't the best. There are saw marks on the edges of the slabs that will take a lot of time to remove.
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Deleted
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Post by Deleted on Feb 20, 2016 18:48:37 GMT -5
Thanks for the reply. For the moment I'm just adding 1 tbsp of grit after every 4 hour run. They're taking a long time because it's pretty hard material (agate and fossilized wood mostly) and the cuts weren't the best. There are saw marks on the edges of the slabs that will take a lot of time to remove. Should not take four hours unless very large slabs. Can you hear the grit cutting the stone? When that sound stops, you have no grit cutting the stone. Time to add more.
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yetiabitibi
starting to shine!
Member since February 2016
Posts: 25
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Post by yetiabitibi on Feb 20, 2016 19:28:43 GMT -5
I can hear the grit rubbing against the slabs. I think I may have the opposite problem though, the slabs are sometimes small and lightweight and I don't have any weights to put on them, so the action of the grit is less aggressive.
My biggest problem is that I have those bloody saw marks on the edges of the stones and even thought they're only a fraction of a millimeter, it's just hard to get rid of them since I have to grind down the whole face of the slab to get it even. I do the pencil test and all the marks are gone, except for in those saw marks.
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Deleted
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Post by Deleted on Feb 20, 2016 22:57:55 GMT -5
#1) get some weights.
#2) grind off the nub using a tile saw blade
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yetiabitibi
starting to shine!
Member since February 2016
Posts: 25
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Post by yetiabitibi on Feb 21, 2016 6:51:24 GMT -5
1) Working on it 2) It's not a nub, its where the saw blade bit in on a slight angle and it causes a slight depression.
Thanks for the advice, it's been quite useful.
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