The axial distance between corresponding points on adjacent threads. Metric threads state it directly in millimeters, such as the 1.25 in M8 x 1.25, while inch threads state its reciprocal as threads per inch. On a single-start fastener, pitch equals lead, the distance the nut advances in one turn; on multi-start threads the two are different.
Pitch looks like one and a quarter, not one and a half, so that M10 is metric fine, don't run that nut on with the gun.
Also heard as
- thread pitch
Do not mix it up with
- Lead: Lead is how far the thread advances per turn; it equals pitch only on single-start threads.
- Pitch diameter: Pitch diameter is a diameter that controls fit, not the spacing between threads.
Related terms
TPI
Threads per inch: the count of thread crests in one inch of length, used to state the pitch of inch threads.
Lead
The distance a thread advances along its axis in one full turn, equal to pitch times the number of starts.
ISO metric thread
The 60-degree metric screw thread, written as M plus diameter and pitch in millimeters, such as M10 x 1.5.
Pitch diameter
The diameter at which thread thickness equals the gap between threads, the dimension that controls fit.