How To Score Polishing Laps


polishing laps - scored tin lap
“Old Faithful” scored tin lap

Why Score Polishing Laps?

In my experience, scored polishing laps work better and faster. I’ve cut a lot of gemstones and tried polishing just about every way imaginable. Of course, you’ll hear different opinions, but all the old pros I know score their laps. I know it’s hard to cut up a pretty new polishing lap. If you’re not sure, you can score it later. After you’ve tried the lap unscored, cutting it won’t hurt anything.

Scoring helps keep the polish on the lap where you want it. Also, it gives the chaff/waste a place to go that won’t scratch your gemstone. I score all of my tin and zinc laps, whether I’m using diamond, aluminum oxide, or cerium oxide.

Scoring Polishing Laps is Easy

There are many ways to score your lap. I use an old piece of hacksaw blade about 2” long, but you can use a razor, knife, or whatever. (I like the hacksaw because it’s fast. It makes lots of grooves at the same time).

To make grooves, scrape your blade from the center (mounting hole) of the lap straight to the outside edge all the way around.

Then, turn the lap 90º and score across it to create diamond-shaped grooves where they cross each other. Those little diamond shapes will hold the polish.

polishing laps - score marks close up
Score marks

After scoring, wipe off the loose bits. Optionally, you can put some polish and water on the lap and use an old piece of garnet or tourmaline to help knock off the burrs. Be sure you don’t use something hard like cubic zirconia. If you accidentally embed a piece, it will cause scratches.

Using Scored Polishing Laps

When your lap is new, you’ll notice some metal accumulates on the edges of your facets. This will wipe off and not hurt anything. Also, there might be some slight rounding. As you break in your lap, it will begin to work harden and not do this much at all. It will polish flatter facets.

The more you use your scored lap the faster and better it will polish. After you’ve used the lap for a while and it seems to slow down, score it again.

polishing laps - hacksaw blade
A piece of hacksaw blade is useful for scoring polishing laps.