In screw terminology, what does lead refer to?

• A. The axial distance the nut advances per complete turn.
• B. The diameter of the screw.
• C. The number of threads per inch.
• D. The overall length of the screw.

Answer: (A)

Lead is the axial distance the nut moves along the screw with one full turn. This describes how far the nut advances for each revolution of the screw. It’s not the screw’s diameter, nor the number of threads per inch (that describes pitch), nor the overall length of the screw. For a single-start screw, lead equals pitch, so one turn moves the nut by that distance. For multi-start screws, lead is pitch times the number of starts, so each turn advances the nut farther. For example, a 3-start screw with a 2 mm pitch has a lead of 6 mm, meaning one full turn moves the nut 6 mm.