Proxxon Diamond Twist Drill Bits 0.8 and 1.2 mm, 2 pcs

Proxxon diamond twist drill bits – for enlarging holes in gemstones

The Proxxon diamond twist drill bit set (art. no. 28255) consists of two diamond-coated bits for enlarging existing holes in semi-precious stones, gemstones and minerals. The set contains one 0.8 mm bit and one 1.2 mm bit. This lets you widen a fine hole step by step to the size you need, for example for jewellery wire or thread.

Both bits have a shank with a diameter of 2.35 mm and an overall length of 44 mm. You therefore need a hand-held tool whose collet takes 2.35 mm, such as a Micromot. The bits have no cutting edges at the tip, so they are intended only for enlarging holes, not for starting a hole in solid stone.

How to enlarge a hole

The hole must already exist in the stone, because the bits cut only at the sides through the diamond coating. Hold the stone securely or clamp it. Keep the drilling point constantly cooled with water, for example in a water bath or with a pipette. Work at approx. 18,000–20,000 rpm and with only light pressure.

• For a very fine hole, start with the 0.8 mm bit.
• Then widen it with the 1.2 mm bit if needed.
• Insert the bit straight and do not tilt it, so that it does not jam.

Proxxon diamond twist drill bits product details

• Manufacturer: Proxxon, art. no. 28255
• Contents: 2 pieces, 1 × Ø 0.8 mm and 1 × Ø 1.2 mm
• Shank diameter: 2.35 mm
• Overall length: 44 mm
• Optimum speed: approx. 18,000–20,000 rpm
• Maximum permitted speed: 50,000 rpm
• Use: enlarging existing holes in semi-precious stones, gemstones and minerals

You will also need: hand-held tool or drill with a collet for a 2.35 mm shank, water for cooling

Always cool with water when drilling, otherwise the diamond coating will be damaged. Do not exceed the maximum permitted speed of 50,000 rpm.