1. What is Thread Minor Diameter?

The minor diameter is the smallest diameter of a screw thread, measured at the root of the thread where the thread meets the shaft. It's a critical dimension for determining thread strength and fit.

2. How Does the Calculator Work?

The calculator uses the thread minor diameter formula:

Where:

• \( \text{minor\_dia} \) — Minor diameter (inches)
• \( \text{major\_dia} \) — Major diameter (inches)
• \( \text{pitch} \) — Thread pitch (inches)
• 1.0825 — Constant factor for standard threads

Explanation: The formula accounts for the relationship between major diameter, pitch, and the resulting minor diameter in standard thread forms.

3. Importance of Minor Diameter Calculation

Details: Accurate minor diameter calculation is crucial for determining thread strength, ensuring proper fit with mating parts, and calculating stress areas for bolted joints.

4. Using the Calculator

Tips: Enter major diameter and pitch in inches. Both values must be positive numbers. The result will be the theoretical minor diameter.

5. Frequently Asked Questions (FAQ)

Q1: Is this formula valid for all thread types?
A: This formula is primarily for standard 60° thread forms (UN, metric). Other thread forms may use different constants.

Q2: How accurate is this calculation?
A: This gives the theoretical minor diameter. Actual manufactured threads may vary slightly due to tolerances.

Q3: What's the difference between minor diameter and root diameter?
A: For external threads, minor diameter and root diameter are the same. For internal threads, they differ slightly.

Q4: Can I use this for metric threads?
A: Yes, but ensure all measurements are consistent (all in inches or all in millimeters).

Q5: Why is the constant 1.0825?
A: This value comes from the geometry of standard 60° threads (2 × 0.54125 × pitch, where 0.54125 is the thread height factor).