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Thread Terminology

External Thread: The mating part with threads on the external surface. Internal Thread: The mating part with threads on the internal surface. ( Nominal Diameter: The theoretical diameter of the threaded assembly. ) Major Diameter: The largest diameter of either the internal or external thread. Minor Diameter: The smallest diameter of either the internal or external thread. Pitch Diameter: A theoretical diameter used to correlate the dimensions between an internal and external thread assembly. Pitch: The distance between like points on a thread and is typically measured between crests. Thread Depth: The distance from root to crest when measuring perpendicular to the thread’s axis. Thread Angle: The included angle from crest to root of each thread. Crest: The surface area of each thread’s peak on either an internal or external thread. Root: The surface area of each thread’s valley on either an internal or external thread.

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THREAD MILLING REFERENCE GUIDE | 5