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Author Topic: Padding or no padding on vertical laps?  (Read 929 times)

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R.U. Sirius

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Padding or no padding on vertical laps?
« on: November 23, 2021, 07:52:12 AM »

I need to decide on parts to buy or build to make my small shop as versatile as possible for cabbing, but also grinding and polishing larger, flat or very low dome pieces of intarsia and such.

When working with vertical lap plates or polishing heads on ends of arbors, how does padding (and firmness and thickness of the pad) change the grinding/polishing behavior of the lap?

If using plated metal laps, of course I will want solid backing without a pad. But if I'm using resin-bonded diamond film or SiC paper discs, or canvas charged with diamond compound, or anything else flexible, I can place it directly on the metal, or have a neoprene pad in between. What is the practical difference?

Also, do I need padding under felt when polishing with Linde A or tin oxide? Felt itself (1/4 inch thick) will have some give to it, no? If padding is there, can felt be made thinner (1/8 of an inch)?

Finally, what temporary adhesive to use that will let me exchange the abrasive materials easily from the bare aluminum, plastic, or padded discs? Is cross-contamination an issue? Should I just have dedicated heads for each grit/type of the abrasive?

Thank you for sharing yoyr insights!
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vitzitziltecpatl

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Re: Padding or no padding on vertical laps?
« Reply #1 on: November 23, 2021, 04:18:13 PM »

For your discs from 280 up, the foam backers allow the disc to conform to the profile of the cab. Easier, and helps prevent faceting. Felt that is a full 1/4" thick might be more than you need.

Feathering disc adhesive is the most common way to attach your laps to the backers.

Over time you'll develop methods that suit you best, but for starting out the standard foam backers work great.

lithicbeads

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Re: Padding or no padding on vertical laps?
« Reply #2 on: November 24, 2021, 11:48:59 AM »

Pads have been a mainstay for me for many years. Foam allows the cab to conform . That is most useful but in a crunch a well worn diamond pad without sponge backing can be n absolute time saver. If you hve a scratch or hazy polish on a stone the well worn pad with hard backing will get the repair job done very quickly unless you really screwed up. The lack of a sponge backing allows you to hit the center of flats more easily for repairs. I use the all u need pads with the worn blue being most useful with no backing. I always have the red pad with no backing available as well. I dress the pads when they get worn. I use  a small diamond drill bit and lightly score the pads as it is turning then wash the pad well. I have used some pads for years doing just touchup work with them. I have saved hundreds of hours on repairs using this method when I was production cutting. To get the pad to be more aggressive for scratch removal wet it lightly nd sand until it is virtually dry. As it dries it will grab the stone as when using a drying oxide polish and become a bit more aggressive but avoiding a coarser pads overall sanding. Less going back and repeating grits. I have used foam about an inch thick about 6 inches in diameter on a 6 inch hard lap with an 8 inch sanding pad on top. Used with variable speed it allows you to get into some recesses on carvings and is a fast money saver.
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vitzitziltecpatl

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Re: Padding or no padding on vertical laps?
« Reply #3 on: November 24, 2021, 06:03:50 PM »

Yes! That last bit about having the edge of a lap draping over the edge of your master lap or backer is a great tip.

Most people wouldn't think to use a lap that way. It isn't "how it's done". You just gave a free bit of wisdom to anyone who reads this.
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