A diamond bur is a small rotary cutting tool whose working head is coated or impregnated with industrial diamond grit bonded to a metal substrate, mounted on a cylindrical shank. Designed to grind, shape, carve, and engrave materials that resist conventional steel tooling, diamond burs are indispensable wherever a jeweller or lapidary must work substances rated above approximately Mohs 7 — including corundum, spinel, topaz, quartz, beryl, and glass. They are driven by flexible-shaft machines, pendant drills, or dental-style handpieces at speeds typically ranging from a few thousand to around 35,000 revolutions per minute, depending on the material and the delicacy of the operation.

Construction and grit grades

The working surface of a diamond bur consists of synthetic industrial diamond particles — selected for consistent hardness and fracture behaviour — electroplated or sintered onto a steel or carbide shank. Electroplated burs carry a single layer of relatively coarse grit and cut aggressively; sintered (metal-bond) burs embed multiple layers of finer grit in a powdered-metal matrix, yielding longer service life and a smoother cut. Grit designations broadly follow the same conventions used in lapidary and abrasive industries: coarse grades (around 60–120 mesh) remove material rapidly and leave a rough surface; medium grades (around 150–400 mesh) are used for shaping and refining; fine grades (600 mesh and above) approach a pre-polish finish on hard stones.

Head geometries

Diamond burs are manufactured in a wide range of head profiles, each suited to a particular task:

• Ball (round) — for concave recesses, bezel interiors, and general carving.
• Cylinder (barrel) — for flat-bottomed seats, channel setting, and inlay work.
• Flame (tapered cylinder with rounded tip) — for prong shaping, detail carving, and reaching confined spaces.
• Cone and inverted cone — for undercutting, bead raising, and angled seat preparation.
• Wheel and disc — for grooving, slotting, and surface texturing.
• Needle — for fine engraving lines and piercing hard materials.

Shank diameters of 2.35 mm (3/32 inch) and 3.0 mm (1/8 inch) are the most common in jewellery bench work, matching the collet sizes of standard flexible-shaft handpieces.

Applications in the jewellery workshop

In stone setting, diamond burs are used to prepare seats in metal for fancy-cut or calibrated stones — refining the depth and angle of a bearing so that a sapphire or ruby sits flush and secure. When setting directly into hard stone mounts or carving intaglio designs into corundum or rock crystal, steel gravers and carbide burs are inadequate; only diamond-coated tooling maintains a cutting edge against such materials. Lapidary carvers rely on ball and flame burs to hollow cabochon backs, open drill holes, and execute sculptural relief work in jade, agate, and similar materials. In glass and ceramic work — including the repair and modification of enamel panels — diamond burs provide controlled material removal without the shattering risk associated with harder impact tools.

Use and care

Effective use of diamond burs requires continuous lubrication and cooling. Water, a water-soluble cutting fluid, or a dedicated lapidary coolant is applied at the point of contact to flush away swarf, prevent heat build-up, and extend the life of the diamond coating. Running a bur dry against hard stone generates sufficient heat to anneal the bond holding the grit, causing premature shedding and tool failure. Light, consistent pressure — allowing the abrasive to do the work rather than forcing the tool — produces cleaner results and reduces the risk of fracturing brittle gemstones. Burs should be inspected regularly; a glazed or loaded surface (one clogged with ground material) can be partially restored by briefly dressing it against a soft aluminium oxide stick, though heavily worn burs are best replaced.

In the trade

Diamond burs are consumable items, and professional bench jewellers maintain a range of profiles and grits as a matter of routine. Quality varies considerably between manufacturers: premium burs from specialist suppliers offer more consistent grit distribution and longer service life than commodity equivalents, a difference that becomes significant when working expensive or irreplaceable gemstone material. For carving or setting work in stones above Mohs 9 — corundum and its varieties — only diamond tooling is practical, making the bur one of the few bench tools for which there is no viable lower-cost substitute.

Further reading

• International Gem Society — Lapidary Tools Overview