ISO 724 Metric Screw Threads – Basic Dimensions & Tap Drill Guide Thread Symbols & Terminology Symbol Definition D, d Major Diameter (Nominal Diameter) – The largest diameter of the thread P Pitch – Distance between corresponding points on adjacent threads (mm) D₂, d₂ Pitch Diameter – Diameter where thread width equals space width (mm) … Continue reading ISO 724 Metric Screw Threads – Metric Tap Drill Table