The major or crest diameter of an external screw thread is identical to_____________________?
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Answer: A. major diameter
Explanation
The major diameter of an external screw thread corresponds directly to the outermost crests of the thread profile. This dimension represents the largest diameter measured across the threaded cylindrical component. Manufacturing standards define the crest diameter and major diameter as identical parameters for external threads. Screw thread geometry involves major, minor, and pitch diameters to define thread profiles accurately. External threads are cut onto cylindrical shafts, while internal threads are tapped inside holes or nuts. Major diameter is the primary nominal size used to specify standard bolts and screws in engineering drawings.
Machinists use micrometers to measure major diameters and verify that external threads meet manufacturing tolerances. Standard fastener catalogs list bolts by their nominal major diameter and thread pitch specifications. Accurate major diameter measurements ensure proper fit and assembly within matching internal threaded holes. Minor diameter measures the innermost root of the thread rather than the outermost crest diameter. Pitch diameter measures the theoretical cylinder where tooth and space widths are equal, not the crest. Core diameter is synonymous with minor diameter, representing the smallest cross-section of the threaded rod.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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