Question 1

What is the difference between pitch diameter and major diameter?

Accepted Answer

Major diameter is the largest diameter of the thread (crest for external threads). Pitch diameter is the diameter where the thread width and space width are equal. For thread fit and strength, pitch diameter is the critical dimension — it determines how the internal and external threads engage.

Question 2

Can I use a thread micrometer instead of three wires?

Accepted Answer

Yes, thread micrometers with specialized anvils that contact the thread flanks provide direct pitch diameter measurement. They're faster than three-wire but less accurate (±0.0005 inches vs. ±0.0002 inches for three-wire). Thread micrometers are adequate for shop-floor inspection, while three-wire is preferred for calibration and certification.

Question 3

How do I measure pitch diameter on a thread mill?

Accepted Answer

Threads produced by thread milling can be measured by the three-wire method. However, the cut thread will follow the tool path, so check at both ends and middle of the thread length. CMM with thread probes offers the most comprehensive inspection for thread-milled features.
⚡ Calculated for Carbide-Tooling.com High-Performance Series. View Catalog →

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