A bit confused about copper laps

I have watched a couple of videos and read a few articles and am a bit confused with copper laps. So far I am using diamond laps but they seem a bit harsh so thought I would try copper.

Anyway, I am confused about using water or not using water.

I noticed that when charging a copper lap with 3000 for a prepolish they are not using any lubricant, but when charging for cutting with 1200, 600 etc they are using water.

What is the reason for using water when cutting and not for polishing?

On copper laps the diamond is usually mixed with a carrier such as vaseline which acts as a lubricate. With coarser laps say 300 to 1200 water is also used to help remove swarf( a mixture of ground up rock, grease and diamond). At the prepolish stage 3000 and up, however the vaseline is sufficient lubrication and less swarf is generated.Of coarse facetors use other carriers such as teflon grease etc rather than vaseline, and lubricates such light oils. Hope this helps.

A plated or sintered diamond lap has the diamond abrasive particles bonded to the surface or embedded into the metal - in my experience they do cut more harshly than a lap that you charge yourself with loose diamond powder and some lubricant, as is evidenced by the difference between a plated #3000 lap which still leaves a lightly frosted surface and loose #3000 grit in an oil or water-based carrier which often leaves a surface looking not that far short of polished (still needs a bit of a "kiss" with #50 000 or above diamond or an oxide polish to finish it right off).

I wouldn't worry too much about the surface after roughing out with a coarse plated lap like #325 or the like - you're going to strip that layer away with a finer lap anyway.

Copper laps seem to put a really good pre-polish on sapphire when charged with #8000 diamond but I've tried using them to do a final polish and it just didn't seem to work all that well.

For final polishing I use a Matrix for most things, it has been an extremely versatile polishing lap for thigs as soft as feldspar to hard as sapphire and everything in between and works equally well with either diamond or oxides.

That said, I do have a variety of other polishing laps, some made of different types of plastic, some metal that I do use occasionally.

fossickeract said:

On copper laps the diamond is usually mixed with a carrier such as vaseline which acts as a lubricate. With coarser laps say 300 to 1200 water is also used to help remove swarf( a mixture of ground up rock, grease and diamond). At the prepolish stage 3000 and up, however the vaseline is sufficient lubrication and less swarf is generated.Of coarse facetors use other carriers such as teflon grease etc rather than vaseline, and lubricates such light oils. Hope this helps.

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Thanks for that explanation. I can continue now without doubt. On the 3000 prepolish I have used olive oil and it seems to work well.

Lefty said:

A plated or sintered diamond lap has the diamond abrasive particles bonded to the surface or embedded into the metal - in my experience they do cut more harshly than a lap that you charge yourself with loose diamond powder and some lubricant, as is evidenced by the difference between a plated #3000 lap which still leaves a lightly frosted surface and loose #3000 grit in an oil or water-based carrier which often leaves a surface looking not that far short of polished (still needs a bit of a "kiss" with #50 000 or above diamond or an oxide polish to finish it right off).

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Very timely as I was prepolishing a new stone last night with 3000 on copper and thought just how well the prepolish actually polishes. Doesn't need a lot to finish. I have a Batt lap with 60000 and that worked beautifully with the first stone.