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 Post subject: New VIdeo on Dressing a Polishing Lap
PostPosted: Thu Oct 11, 2018 1:38 pm 
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I hope this will cause lots of discussion around techniques

It's been a while since my last episode but here is a special episode of World of Faceting Machines that presents a traditional technique for scoring/scratching the polishing lap in order to improve speed and polishing performance.


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 Post subject: Re: New VIdeo on Dressing a Polishing Lap
PostPosted: Thu Oct 11, 2018 7:57 pm 
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If the polishing laps that you purchase or have reconditioned were turned on a lathe with precision bearings and use sharp diamond tooling, the surface will be mirror to the unaided eye and will produce an optically flat facet surface when used for polishing.

This method from Sri Lanka is obsoleted by modern precision machinery and diamond tooling.

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Last edited by thomas.adamas on Fri Oct 12, 2018 7:37 am, edited 1 time in total.

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 Post subject: Re: New VIdeo on Dressing a Polishing Lap
PostPosted: Thu Oct 11, 2018 8:10 pm 
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Yes but you haven’t told me why. Once we did this process in the video we got a fine smooth shine. But over the course of cutting many stones, polishing gets slow or possibly we get a scratch on the stone so we rescore the lap. This makes a notable improvement in speed and polish quality. I know what the positive aspect is, but What’s the negative aspect of doing it?

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 Post subject: Re: New VIdeo on Dressing a Polishing Lap
PostPosted: Thu Oct 11, 2018 8:54 pm 
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The negative aspect is that you disrupt the polycrystalline properties of the metal surface. For example, on the BATT and BA5T, the embedding of diamond particles will decrease, which in turn slows down the rate of polishing. I have no information what occurs with the lap used in your video which appears to be copper.

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 Post subject: Re: New VIdeo on Dressing a Polishing Lap
PostPosted: Fri Oct 12, 2018 6:01 am 
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The raised material on either side of the score would be an easy place for the diamond to embed, wouldn't it?
Both by being somewhat weaker than the rest of the surface and being an impact/pinch zone for the embedding tool.

In addition you could still see and feel the grooves after the lap was fully charged. There wouldn't be sudden changes in lap height but the wavey pattern would provide an oscillation in pressure and allow for clearing of swarf in the style of millstones. So it would be more aggressive in comparison to an un-scored surface.

Of course, maybe it's just an easy way to get under any work hardening that the grinding might create, it is copper after all...


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