aeronautee
starting to shine!
Member since September 2011
Posts: 25
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Post by aeronautee on Nov 5, 2021 15:18:55 GMT -5
Now that I've finished my flat lap project, I need advice on lap disc selection. What is the better long-term choice: PSA discs w/backers or topper discs with a master disc. Thanks!
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Post by hummingbirdstones2 on Nov 5, 2021 20:52:14 GMT -5
You'll want steel toppers for at least the coarse grits, say up to 325 - or whatever is close to that in the brand you choose.
Your resin discs should start in the 220-325 range, so you have coarser ones to help in smoothing your domes.
A real time-saver would be thin plastic (or sheet metal) backers for your foam pad/resin disc combos. No mucking about with feathering adhesive each time you want to swap out a resin disc for the next grit. I cut mine from stainless sheet I had on hand. It'll cost a few bucks for foam pads and backers if you have to buy them, but it will make your life so much easier.
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Post by knave on Nov 5, 2021 20:55:34 GMT -5
You'll want steel toppers for at least the coarse grits, say up to 325 - or whatever is close to that in the brand you choose.
Your resin discs should start in the 220-325 range, so you have coarser ones to help in smoothing your domes.
A real time-saver would be thin plastic (or sheet metal) backers for your foam pad/resin disc combos. No mucking about with feathering adhesive each time you want to swap out a resin disc for the next grit. I cut mine from stainless sheet I had on hand. It'll cost a few bucks for foam pads and backers if you have to buy them, but it will make your life so much easier.
I’m considering making my own flat lap but I’m torn I want the nice discs with no hole in the middle. So I’d be stuck with magnetic or Velcro yes?
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Post by hummingbirdstones2 on Nov 5, 2021 21:16:54 GMT -5
Some brands offer no-hole discs. You'd just have to use them on a polishing head with a threaded stud on the back. Separate head for each, or feathering adhesive to swap them out at each step.
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Post by hummingbirdstones on Nov 5, 2021 21:24:19 GMT -5
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Post by knave on Nov 5, 2021 21:57:55 GMT -5
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aeronautee
starting to shine!
Member since September 2011
Posts: 25
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Post by aeronautee on Nov 6, 2021 9:02:54 GMT -5
I should clarify that all I want to do is face polish agates, jasper, etc. that I've cut. Unfortunately, I don't have the skill, knowledge or equipment to create cabs.
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Post by hummingbirdstones2 on Nov 6, 2021 9:43:51 GMT -5
Steel toppers should work for your face polishing. You might need a slightly domed leather for the final step.
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Post by hummingbirdstones on Nov 6, 2021 10:34:06 GMT -5
What Vince said. If I were just face polishing, I'd use all steel toppers and no resin discs. The give in the resin discs will make it harder to do a flat slab evenly.
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aeronautee
starting to shine!
Member since September 2011
Posts: 25
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Post by aeronautee on Nov 6, 2021 11:25:53 GMT -5
To follow up, what grit sequence would be appropriate?
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Post by knave on Nov 6, 2021 14:13:13 GMT -5
The standard grit sequence is something like, 80, 220, 600, 1200, 3000 When switching to soft you add in a 280 but you won’t be doing that.
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Post by hummingbirdstones on Nov 6, 2021 21:36:30 GMT -5
The standard grit sequence is something like, 80, 220, 600, 1200, 3000 When switching to soft you add in a 280 but you won’t be doing that. I would maybe do something like 80 (if the face has saw marks - otherwise I would skip the 80), 180, 260, 600, 1200, 3000.
80 grit scratches on flat surfaces are a total bear to get out. I would maybe start with a 100 or 120 grit if you don't have saw marks. Also, depending on the hardness of the material you are polishing, you'll want to start with an appropriate rough grit. Softer material, you'll want to avoid the really rough grits.
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aeronautee
starting to shine!
Member since September 2011
Posts: 25
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Post by aeronautee on Nov 7, 2021 10:17:08 GMT -5
The standard grit sequence is something like, 80, 220, 600, 1200, 3000 When switching to soft you add in a 280 but you won’t be doing that. I would maybe do something like 80 (if the face has saw marks - otherwise I would skip the 80), 180, 260, 600, 1200, 3000. 80 grit scratches on flat surfaces are a total bear to get out. I would maybe start with a 100 or 120 grit if you have saw marks. Also, depending on the hardness of the material you are polishing, you'll want to start with an appropriate rough grit. Softer material, you'll want to avoid the really rough grits.
As a woodturner, that progression is more like what I'm familiar with, i.e. 80 to 120 to 180, etc. The question now is how much should I be spending? Kingsley North has top plates for $20. The Rock Shed runs more than twice that; The Lapidary Mart is more, yet. Getting what you pay for, I don't want to buy too cheap, but I don't want to have to take a second mortgage on the farm, either.
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Post by hummingbirdstones on Nov 7, 2021 17:08:09 GMT -5
I have some really cheap ones that I bought off of Ebay. They work fine for what I use them for. Doesn't hurt so much when you have to replace a cheap one.
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aeronautee
starting to shine!
Member since September 2011
Posts: 25
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Post by aeronautee on Nov 9, 2021 9:15:42 GMT -5
Thank you to everyone for taking the time to help me out. Someday I hope to be able to offer information instead of having to ask for it!
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