1. What is Pitch Diameter?

The pitch diameter is the diameter of an imaginary cylinder that passes through the threads where the width of the thread and the width of the groove are equal. It's a fundamental measurement in thread design and manufacturing.

2. How Does the Calculator Work?

The calculator uses the metric thread pitch diameter formula:

Where:

• Major Diameter — The largest diameter of the thread (mm)
• Pitch — The distance between thread crests (mm)
• 0.6495 — Constant for metric threads (derived from thread geometry)

Explanation: The formula accounts for the relationship between major diameter and thread pitch in metric thread standards.

3. Importance of Pitch Diameter

Details: Pitch diameter is crucial for determining thread fit, strength, and interchangeability. It's used in quality control and thread gauge design.

4. Using the Calculator

Tips: Enter major diameter and pitch in millimeters. Both values must be positive numbers. Standard metric thread values can be found in engineering references.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between major and pitch diameter?
A: Major diameter is the largest diameter of the thread, while pitch diameter is the diameter where thread and groove widths are equal.

Q2: Does this formula work for all thread types?
A: No, this specific formula is for metric (ISO) threads. Other thread standards (UN, Whitworth, etc.) have different formulas.

Q3: Why is 0.6495 used in the formula?
A: This constant comes from the geometry of the 60° thread angle in metric threads (√3/4 ≈ 0.6495).

Q4: How accurate is this calculation?
A: The formula provides theoretical values. Actual manufactured threads may have tolerances specified in standards.

Q5: Where is pitch diameter most important?
A: In thread fits (clearance vs. interference) and when using thread measuring wires for inspection.