1. What is Metric Thread Effective Diameter?

The effective diameter (also called pitch diameter) of a metric thread is the diameter of an imaginary cylinder that passes through the threads where the width of the thread and groove are equal. It's a critical dimension for thread fits and strength calculations.

2. How Does the Calculator Work?

The calculator uses the standard metric thread formula:

Where:

• \( d \) — Nominal diameter of the thread (mm)
• \( P \) — Pitch of the thread (mm)
• 0.6495 — Constant for ISO metric threads

Explanation: The formula accounts for the relationship between nominal diameter and pitch to determine the effective diameter where the thread makes contact.

3. Importance of Effective Diameter

Details: Effective diameter is crucial for determining thread fits, calculating thread strength, and ensuring proper mating of threaded components. It's the most important dimension for thread gauging.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

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

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

Q3: How accurate is this calculation?
A: The formula provides theoretical values. Actual manufactured threads may vary slightly within tolerance limits.

Q4: Where is effective diameter used in practice?
A: It's used in thread gauging, determining thread fits (e.g., H7/g6), and calculating thread stripping strength.

Q5: Can I use this for internal threads?
A: The same formula applies to internal threads, but the interpretation of the dimensions is different for holes.