Fine thread bolts are thought to be stronger since the shallow thread disrupted the base material less, providing a large minor diameter
Used when fine dimensional adjustments are required
Fine threads have less tendency to loosen since the thread incline is smaller and hence is the off torque
Fine threads can be easily tapped into hard materials and thin walled tubes
Fine thread require less torque to develop equivalent bolt preloads
Bolts with hexagon heads and thread are used with a nut or tapped hole
What does 8.8 mean: The number before the point is the Tensile ultimate strength in MPa divided by 100. The number after the point is 10 times the ratio of tensile yield strength to tensile ultimate strength. 8.8 = (minimum) ultimate tensile strength of 800MPa, and a tensile yield strength of 0.8 times tensile ultimate strength or (0.8 x 800) 640MPa
