tags: #publish links: [[Gemstone Faceting equipment]] created: 2023-01-09 Mon --- # Zinc Plus lap From Gearloose A laminated zinc lap. Harder and more aggressive than [[Batt lap]], cuts more with finer grades of diamond e.g. 8k+ will happily move facets. Good for efficient pre-polish. ## How to use I use this with 8k diamond as pre-polish. I started out with 14k but found it can be a bit slow to remove deeper pits and scratches or move meets, so I switched it to 8k. Works fine with both "pandimonium" diamond sticks, and loose bort with "snake oil". My learning so far (note - I'm a beginner at this point - written after only a couple of stones!) - Run it fairly dry. It needs *some* oil, but not a slick of it. Oil, no water. - Run it fairly fast, e.g. I'm running mine at >40% of my machine's speed. - **To charge it**, do the same thing as in Gearloose's [[Batt lap]] how to: http://www.battlap.com/battman.html - Wipe oil over it (I apply at most 1-2 sprays from a tiny 50ml spray bottle, often less) - Evenly spread (e.g. with your finger at a slow speed) a *small* amount of bort, e.g. less than an oily fingertip's pickup. - Or, draw 2-4 very light radial lines with the pandimonium stick, emphasising the outer areas. - I find that after this application, I can just start cutting without spreading further. The cutting spreads it and pushes it into the lap, as long as you don't have things *too* dry. But need to keep a close watch that it doesn't start balling up into scratchy swarf. - I don't wipe off excess straight away. Usually do need to wipe after a couple of minutes as swarf happens. - The very first time, I applied (too much) oil and bort and used a boule of synthetic corundum to try to push it in. - The corundum needs to be already flattened and smoothed with (say) a 600 lap, otherwise the protruding points and sharp edges on the corundum will score the zinc lap, because it doesn't have any embedded diamond yet! - I am not sure this step is really needed. I think you could just apply a decent amount of oily bort (maybe more than usual), start cutting carefully, and reapply often at first. - When cutting slows down, you need to wipe off and then reapply diamond. Here are the signs to watch for: - **Feel:** - You should not have to press hard. I use light to at most moderate pressure. When charged it should feel slightly abrasive, not like just oily smooth metal. When undercharged it will cut more if you press harder, but will often then lead to scratching and vibration, and it's still pretty slow compared to light pressure when well charged. - **Sound:** - You can hear it too, when well charged it should sound slightly abrasive rather than just metallic or smooth polishey. - If you hear a gritty sound, you need to stop and clean up swarf, cos you're about to get swarf scratches. - **Lap surface:** - If you get metal filings or scoring, yikes, recharge! This only happened a couple of times very early before it was charged properly. - If you see patches of black swarf building up, you need to stop and clean up swarf, cos you're about to get swarf scratches. By the time the swarf is visible as black stuff, there's already quite a lot of swarf in a thin film. - **Cutting behaviour, facet surface:** - It will leave a bit of greasy stuff on the facet. - If it just leaves a mirror or facet looks dryer, it's probably undercharged. - Simultaneously the lap surface will just look like shiny metal with little evidence of abrasive. This means the repeated swarf build up and wipe-off has removed too much of the diamond and oil. - When cutting with 8k or 14k the cutting will leave a little bit of wavy parallel lines from the lap surface. - If it starts getting too mirror-ish then you're probably under-charged. It will still work to an extent but it gets very slow. It's supposed to be a fast lap! - When well charged, it should cut quite quickly e.g. a couple of sweeps has a noticeable abrasive effect. - When the above behaviours change, there's two different next steps, depending how much diamond is still left (which you can tell based on how well it's cutting): - **1. Remove swarf**. You can repeat this several times and continue without recharging with diamond. - Keep the lap spinning - Spray on a tiny bit of oil (like, only a couple of drops are needed, just enough to loosen the swarf. You don't want to remove *all* the diamond yet just keep the swarf under control). - Wipe off the worst of the swarf with a clean paper towel. It will pick up oily black stuff. Repeat with a new spot on the towel, adding more oil if it gets too dry to pick up. Continue while there's obvious heavy swarf deposits (e.g. may take 3-4 wipes and 2 oil sprays) until you only pick up a little grey colour, rather than thick charcoal black stuff. - Spray a tiny bit more oil and keep cutting. - **2. Recharge with diamond**. When cutting slows down and it's not abrasive enough, clean off a bit more than before, and recharge with diamond - the same as the initial charge, just less of it. Don't wipe off too much of it straight away, do a bit of cutting to spread it around. Other tips: - Your facet is going to get oily and pick up a bit of paste. This will conceal the scratches and pits and edge chipping you're trying to remove. So use a damp (with water) bit of paper towel to wipe with, before looking. Look at several different angles, off from the light axis, moving the light or stone or viewpoint around, to catch the light on the scratches instead of the facet. Wipe in a different direction to check. ## Official instructions ![[20230109_202351.jpg]]