Laps are the bases used for polishing and cutting rough gems into fine gemstones. There is a wide range of available laps in use, and many of them are original creations used exclusively by the developer. Generally, however, polishing laps fall into several basic classifications.
A Lucite lap is very popular. Its hardness, which is approximately 2, indicates some limitations, but Lucite has performed well and is versatile. A combination lap made of equal amounts of lead and tin is also in general use.
Another polishing lap often found in regular use is the “typemetal lap.” Its alloy of lead, copper, antimony and tin hint at the general softness of this lap, but lead is tough and tends to give added wearing ability when used.
Tin laps are also in common use, as are lead laps. Practically every type of material seems to have been experimented with, and many of them have been successful, especially when a specific need arises. Incidentally, the fine book, “Faceting for Amateurs,” by Glenn and Martha Vargas, covers the data on laps extensively. Most Rock Shops stock the book, and its 330 pages make interesting reading for beginner or expert.
In general, the Lucite lap is popular because it’s inexpensive, but a lubricant is vital t0 minimize the heat that develops.
This entire post could easily be devoted to the diamond laps. The most popular are the basic cutting laps such as the 120 grit or the 100. A 400 for fine facet cutting is used on practically every stone, while an extra-fine finish can be applied through the use of a 1200 grit lap. The most popular one in regular use is a 3000 diamond lap that pre-polishes and minimizes the amount of time involved in completing a polish. Although there are finer laps on the market, we have been unable to use one with a free conscience, as the lap is easy to damage, and extra caution is required in using finer laps. This is not to say that the diamond compounds ranging to 5000 grit size cannot be easily used on copper laps, etc. The compounds work well, but if you can afford the all-diamond laps, chances are their durability, ease and workability will make them a very satisfactory investment.
If you are a beginner and all this talk about the wide range of available laps is confusing you, your best bet is to talk to hobbyists who are already in the field or other handcrafted jewelry designers. Chances are, if you,talk to a number of them, you will soon see the total picture. Don’t stop with a single cutter, as the probability is strong that he has personal favorites which may not be in the same field as your requirements. Although you can work very well with a lap or two, you will find that part of the fun in cutting is to experiment. My workshop has several dozen laps but this is a luxury. For the average hobbyist, only a few laps are vital, so check your needs against your budget, and decide how extensive your lap stockpile need be.