Cup Burr Size Guide: Wire Gauge & mm Conversion

Use this guide to choose the correct carbide cup burr for your wire finishing needs. Match the burr size to your wire diameter or gauge for smooth, professional results.

Cup Burr Size	Best for Wire Size (mm)	Equivalent Gauge (AWG)	Notes
0.9mm	0.6mm – 0.9mm	Thinner than 22 gauge	Ideal for fine wire, e.g. ear wires, jewellery pins
1.0mm	< 0.81mm	Thinner than 20 gauge	Great for standard jewellery wire finishing
1.2mm	< 1.02mm	Thinner than 18 gauge	For slightly thicker wire used in findings or jump rings
1.8mm	Up to 1.63mm	Up to 14 gauge	For thicker wire used in structural or decorative elements
2.1mm	Up to 2.05mm	Up to 12 gauge	Best for heavy-gauge wire, including metalwork or large loops

Cup burrs are also sometimes referred to as wire rounders, wire rounding tool, cup burs, bur cups and deburrers.

The size of the cup bur you choose should be just a hair larger than the wire you plan to use it on. For example, if you use 21-gauge (which is 0.723mm in diameter) to make ear wires, then you would want to use a cup bur of 0.8mm, or 1.00mm.

Tip: If using your wire rounding tool in a rotary tool, be sure to go nice and slow as you may find the metal adhering to the concave part of the cup, clogging it up with swarf.

“I use the cup burrs to round off the ends of taper pins which have been cut with side cutters. I use them hand-held in a pin vice. The tapered pins are soft and are used in clock making/restoration and a taper pin left unfinished looks unsightly. Thanks for providing excellent products and service” - Tony Roberts