Metric thread calculator finds tap drill, pitch diameter, and minor diameter for a standard metric ISO thread from its major diameter and pitch.
How it works
Metric threads are specified by major diameter and pitch directly, for example M10x1.5, unlike unified threads which use threads-per-inch. Pitch diameter and minor diameter both scale directly with pitch; a coarser pitch removes more material at both the pitch and minor diameters relative to the major diameter.
FAQ
Why is my tapped hole loose or tight? Tap drill size directly controls percentage of thread engagement. Too large a drill under-cuts the thread and leaves it loose and weak; too small overloads and can break the tap. Most general-purpose taps target roughly 65 to 75 percent thread engagement.
Related Guides
CNC Calculators · Unified Thread Calculator · Thread Turning Calculator