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REFERENCE · 6 MIN READ

Understanding lap grits and progressions.

A reference on grit ladders, mesh-to-micron conversions, and the conventional sequencing of cutting and polishing 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.

Mesh and micron

Diamond and abrasive grits are quoted in either mesh (U.S. customary) or micron (international). The two systems are not interchangeable across the full range; conversion is approximate and depends on the screening standard. Common landmarks:

  • 60 mesh ≈ 250 µm
  • 220 mesh ≈ 63 µm
  • 600 mesh ≈ 25 µm
  • 1,200 mesh ≈ 12 µm
  • 3,000 mesh ≈ 6 µm
  • 8,000 mesh ≈ 3 µm
  • 14,000 mesh ≈ 1 µm
  • 50,000 mesh ≈ 0.5 µm
  • 100,000 mesh ≈ 0.1 µm

Above 14,000 mesh the screening method is no longer practical and the grit is sized by sedimentation or laser diffraction.

Grit ladder

A typical bench faceting workflow uses a grit ladder of three to five distinct stages:

  1. Coarse cutting (260–600 mesh). Removes bulk material; establishes the cut girdle and pavilion outline.
  2. Fine cutting (600–1,200 mesh). Shapes facet faces and removes scratches from the coarse stage.
  3. Pre-polish (3,000–8,000 mesh). Reduces surface roughness in advance of polish.
  4. Polish (14,000–100,000 mesh, or oxide compound). Establishes the final optical surface.

Some workflows compress the cutting stages into two; some add an intermediate at 1,800 mesh. Selection depends on the species being cut and the cutter's preference.

Bond and grit interaction

Lap bond — the matrix that holds the abrasive grains — interacts with grit selection. Sintered metal bonds are common at coarse-cutting grits because they expose fresh diamond as the matrix wears. Resin and ceramic bonds dominate the pre-polish range. Adhesive PET sheets (the Spectra Ultralap product family) are used on master plates for the polish stage.

Conventions across major brands

Brand-specific naming for the same effective grit varies. The Crystalite "1,800 grit" lap, the Spectra Ultralap "8K" sheet, and the BATT "8000" are all positioned in the late pre-polish stage; their working behavior differs by bond and substrate but the notional grit position is similar. Manufacturers document grit positioning on packaging and in catalog cards.

Lap consumable behavior

Diamond cutting laps wear over time. Sintered laps may last hundreds of cutting hours; plated laps typically last fewer because their abrasive layer is a single monolayer. Polishing laps and adhesive sheets are replaced more frequently. Replacement cadence is workflow-dependent and is not specified to a number by manufacturers.

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