Centre drill (Presto Brand) - 2.5mm pilot hole

Metric

Imperial

Centre drill - 2.5mm pilot, 6.3mm body

6mm (Bock #5 housing)

7.0mm

7.3mm (Presto brand)(Bock #6 housing)

8.1mm (Tempest lower tube)

8.2mm (Mistral BP/PC lower tube)

8.3mm

8.5mm (for 3/8 UNF thread taps)

9.0mm

9.1mm

9.6mm

10.0mm (Mistral BP/PC accent ring)

10.2mm (Presto Brand)

10.3mm (Tempest upper tube)

10.5mm (Cyclone lower tube)

10.7mm (Mistral BP/PC upper tube)

11.0mm

11.1mm (Mistral FP/RB accent ring)

11.2mm (Presto Brand)

11.5mm

11.9mm

12.2mm (Presto Brand)

12.3mm

12.5mm (Cyclone upper tube)

13.2mm (Presto Brand)

13.5mm

14.25mm (Presto Brand)