Tapping Screw Gauge to Metric Size
The nominal diameter of a self tapping screw can be identified in metric mm or imperial gauge size.
For example a No.6 gauge self tapping screw is also a 3.5mm self tapping screw. The nominal diameter can be measured across the threaded portion of the tapping screw.
The accompanying table shows imperial gauge diameters and their metric equivalent.
Gauge | No.2 | No.4 | No.6 | No.7 | No.8 | No.10 | No.12 | No.14 | No.16 |
---|---|---|---|---|---|---|---|---|---|
mm | 2.2 | 2.9 | 3.5 | 3.9 | 4.2 | 4.8 | 5.5 | 6.3 | 8.0 |

For more detailed information please view the following pages:
Square Drive Pan Tapping Screw Standard
Square Drive Csk Tapping Screw Standard
DIN 7981 Pozi Pan Tapping Screw Standard
DIN 7981 Phillips Pan Tapping Screw Standard
DIN 7976 Hex Head Tapping Screw Standard
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