The relationship between spanner (or wrench) sizes and nut sizes typically depends on the nut's dimensions, particularly the width across flats (the distance between two parallel sides of the nut). Below is a general guide for spanner sizes corresponding to standard metric and imperial nut sizes:
Metric (ISO) Nuts:
M6 Nut: Spanner Size = 10 mm
M8 Nut: Spanner Size = 13 mm
M10 Nut: Spanner Size = 17 mm
M12 Nut: Spanner Size = 19 mm
M14 Nut: Spanner Size = 22 mm
M16 Nut: Spanner Size = 24 mm
M20 Nut: Spanner Size = 30 mm
M24 Nut: Spanner Size = 36 mm
Imperial (UNC/UNF) Nuts:
1/4" Nut: Spanner Size = 7/16" (11.1 mm)
5/16" Nut: Spanner Size = 1/2" (12.7 mm)
3/8" Nut: Spanner Size = 9/16" (14.3 mm)
7/16" Nut: Spanner Size = 5/8" (15.9 mm)
1/2" Nut: Spanner Size = 3/4" (19.1 mm)
9/16" Nut: Spanner Size = 13/16" (20.6 mm)
5/8" Nut:Spanner Size = 15/16" (23.8 mm)
3/4" Nut: Spanner Size = 1-1/8" (28.6 mm)
Key Points:
Width Across Flats (WAF): This is the distance between two opposite sides of the nut and typically determines the spanner size.
Tolerance: Always ensure to use the exact spanner size for the corresponding nut size, as a loose fit can lead to rounding off the corners of the nut.
This guide is generally applicable but always refer to specific standards or manufacturer recommendations if available.
