The formula to calculate the effective thread length (L_e) is:
\[ L_e = L_n - H_h - T_r \]
Where:
Let's say the nominal length of the fastener (L_n) is 50 mm, the head height (H_h) is 5 mm, and the thread runout (T_r) is 2 mm. Using the formula:
\[ L_e = 50 - 5 - 2 \]
We get:
\[ L_e = 43 \, \text{mm} \]
So, the effective thread length is 43 mm.