Facetting.
FACETTING.COM · A CATALOGUE FOR THE TRADE
REFERENCE · 6 MIN READ

Types of laps used in gem cutting.

A taxonomy of the rotating discs used for coarse cutting, pre-polish, and final polish stages.

Contents · general reference
01Overview of lapidary equipment categories8 MIN02What is a faceting machine?4 MIN03Types of faceting machines5 MIN04Types of laps used in gem cutting6 MIN05Understanding lap grits and progressions6 MIN06Introduction to dops and transfer systems5 MIN07Overview of common rough gemstone materials8 MIN08Gemstone hardness and cutting difficulty overview5 MIN09Polishing compounds overview5 MIN10Measurement instruments in lapidary and gemmology5 MIN
Contents · gemstone overviews
G01Corundum rough overview5 MING02Quartz rough overview5 MING03Beryl rough overview5 MING04Garnet rough overview5 MING05Tourmaline rough overview5 MING06Topaz rough overview5 MING07Peridot rough overview4 MING08Spinel rough overview4 MING09Chrysoberyl rough overview4 MING10Zircon rough overview4 MIN
About this entry

This reference entry describes categories of equipment and material encountered in the lapidary trade. Definitions, typical specifications, and usage ranges are drawn from published manufacturer documentation and standard glossaries. It does not constitute instruction, training, or professional advice. Readers interested in acquiring equipment should consult a qualified retailer or craftsperson.

Where a manufacturer or product name appears in the text, it is illustrative. Links to retailer listings elsewhere on the site are affiliate links and are disclosed as such.

Definition

A lap is a rotating disc mounted to the horizontal spindle of a faceting machine, against which a gemstone preform is held at a controlled angle. The lap's surface performs the cutting or polishing work; the machine provides rotation, alignment, and stone holding.

Classification by bond

Laps are classified principally by the bond that holds the abrasive material to the substrate. Common bond types include:

  • Sintered metal. Abrasive grains are densely packed in a metal matrix and fused under heat and pressure. Long working life and aggressive cut rate.
  • Plated. A single monolayer of abrasive grains is electroplated to a steel substrate. Relatively short working life but exposes fresh cutting edges quickly.
  • Resin-bonded. Abrasive grains are embedded in a resin matrix that wears gradually, exposing fresh material. Standard for pre-polish stages.
  • Ceramic or composite. Used for fine-grit polishing; bond structure varies by manufacturer. Examples include Crystalite, Dynasty, and Last Lap lines.
  • Tin-bonded ("BATT"). A specific pre-polish and polish lap format using a soft tin-alloy matrix; identified with Gearloose Lapidary's BATT product line.

Classification by grit

Grit is measured in mesh count (U.S.) or micron rating. Common cutting-lap grits run from 60 to 3,000 mesh; pre-polish commonly falls in the 3,000 to 14,000 range; final polish is performed at 50,000 mesh and finer, or with oxide polishing compounds applied to a master lap.

Master laps

A master lap is a bare substrate plate (typically aluminum or steel) used as a carrier for polishing compounds such as cerium oxide, tin-lead alloys, or diamond paste. The master lap itself is essentially non-consumable; the charged medium is the working surface and is replenished periodically.

Diameters

Laps for bench faceting machines are commonly produced in 6-, 8-, and 10-inch diameters. The 8-inch format is the de facto standard in North American practice. Spindle hole diameters are typically 1/2 inch.

Consumable behavior

Diamond cutting laps may last many hundreds of cutting hours. Polishing laps and adhesive polish sheets are replaced more frequently; adhesive sheets typically last for a single stone or a small number of stones depending on species.

© MMXXVI · FACETTING.COM