If a screw has a lead of 1.25 mm, what is the axial advance per complete turn?

• A. 1.25 mm
• B. 0.625 mm
• C. 2.5 mm
• D. 1.0 mm

Answer: (A)

The distance the nut moves along the screw in one full turn is called the lead. So the axial advance per complete turn is exactly the lead value given. With a lead of 1.25 mm, each full rotation advances 1.25 mm along the screw’s axis.

A quick context: pitch is the distance between adjacent threads. For a single-start screw, lead and pitch are the same. If there are multiple starts, lead equals pitch times the number of starts. That’s why 0.625 mm could be the pitch for a two-start screw whose lead is 1.25 mm, but the axial advance per turn remains 1.25 mm. The other numbers would correspond to different situations (like the distance after more than one turn).