A 3.2×12-mm or 1/8×1/2" rivet has approximately a 7.9-mm grip range.
A 3.2×12 rivet has a diameter of 3.175 mm (or 1/8") and a length of 12.7 mm (or 1/2"). We find the grip range by subtracting 1.5 times the rivet's diameter from its length.
In equation form, that is:
12.7 mm - 1.5 × 3.175 mm = 7.9375≈ 7.9 mm. Read more