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A letter code and numbers naming a screw thread completely.
Also known as: Screw thread callout, Metric thread marking
A thread is specified by a code naming its form, diameter, pitch and tolerance class — M for ISO metric, UNC and UNF for the American unified series, G for pipe threads. Threads of the same diameter in different series will not mate, which is what the designation exists to prevent.
Specifies a screw thread's form, nominal diameter, pitch and tolerance class in a single coded designation.
Contexts: Technical drawing
Names the series as well as the size, because threads of the same nominal diameter in different series have different pitches and profiles and will not assemble.
Contexts: Technical drawing
A capital letter followed by numerals and sometimes a multiplication sign, printed as a note with a leader.