Drill Bit Sizes - Center Drill Bit Sizes

Center Drill Bit Sizes

Center drills are available with two different included angles; 60 degrees is the standard for drilling centre holes (for example for subsequent centre support in the lathe), but 90 degrees is also common and used when locating holes prior to drilling with twist drills.

Size Designation Drill Diameter
5/0 0.010 in (0.254 mm)
4/0 0.015 in (0.381 mm)
3/0 0.020 in (0.508 mm)
2/0 0.025 in (0.635 mm)
0 1⁄32 in (0.794 mm)
1 3⁄64 in (1.191 mm)
2 5⁄64 in (1.984 mm)
3 7⁄64 in (2.778 mm)
4 1⁄8 in (3.175 mm)
4½ 9⁄64 in (3.572 mm)
5 3⁄16 in (4.763 mm)
6 7⁄32 in (5.556 mm)
7 1⁄4 in (6.350 mm)
8 5⁄16 in (7.938 mm)
Gauge
BS1 1⁄8 in (3.175 mm)
BS2 3⁄16 in (4.763 mm)
BS3 1⁄4 in (6.350 mm)
BS4 5⁄16 in (7.938 mm)
BS5 7⁄16 in (11.113 mm)
BS5A 1⁄2 in (12.700 mm)
BS6 5⁄8 in (15.875 mm)
BS7 3⁄4 in (19.050 mm)


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