1. What is Bolt Circle Diameter?

The Bolt Circle Diameter (BCD) is the diameter of the circle that passes through the center of all the bolt holes in a circular pattern. It's a crucial measurement in mechanical engineering, particularly for flange designs, gear assemblies, and wheel hubs.

2. How Does the Calculator Work?

The calculator uses the BCD formula:

Where:

• \( Chord \) — The straight-line distance between centers of two adjacent holes (mm)
• \( n \) — Number of equally spaced holes in the circle
• \( \pi \) — Mathematical constant (approximately 3.14159)

Explanation: The formula calculates the diameter of the circle that would pass through all bolt centers based on the distance between adjacent bolts and the number of bolts.

3. Importance of BCD Calculation

Details: Accurate BCD measurement is essential for proper fitting of components, ensuring bolt patterns match between mating parts, and maintaining structural integrity in mechanical assemblies.

4. Using the Calculator

Tips: Measure the chord length (distance between centers of two adjacent holes) in millimeters, count the number of holes, and enter these values. The calculator will determine the BCD.

5. Frequently Asked Questions (FAQ)

Q1: What's the minimum number of holes needed?
A: The calculator requires at least 3 holes to form a meaningful bolt circle.

Q2: How precise should my chord measurement be?
A: For accurate results, measure to at least 0.1 mm precision, especially for small bolt circles.

Q3: Can I use this for non-metric measurements?
A: While the calculator uses mm, you can convert inches to mm (1 inch = 25.4 mm) for imperial measurements.

Q4: What if my bolt pattern isn't perfectly circular?
A: This calculator assumes a perfect circular pattern. For irregular patterns, more complex calculations are needed.

Q5: How does hole size affect the calculation?
A: The calculation uses hole centers, so hole size doesn't affect BCD (but is important for clearance).