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 critical measurement in mechanical engineering, particularly for designing flanges, gears, and wheel hubs.

2. How Does the Calculator Work?

The calculator uses the BCD formula:

Where:

• \( Chord\ Length \) — Distance between centers of two adjacent bolts (inches)
• \( Number\ of\ Bolts \) — Total count of bolts in the circle

Explanation: The formula calculates the diameter of the circle based on the chord length between two adjacent bolts and the number of bolts in the pattern.

3. Importance of BCD Calculation

Details: Accurate BCD measurement is essential for proper fitment of components, ensuring bolt alignment, and maintaining structural integrity in mechanical assemblies.

4. Using the Calculator

Tips: Measure the center-to-center distance between two adjacent bolts and count the total number of bolts in the circle. Enter these values to calculate the BCD.

5. Frequently Asked Questions (FAQ)

Q1: What if I can only measure between non-adjacent bolts?
A: The formula can be adapted for non-adjacent bolts by adjusting the angle in the denominator (360° × number of skipped holes / total bolts).

Q2: How precise should my measurements be?
A: For most applications, measurements to 1/64" (0.0156") are sufficient, but precision applications may require greater accuracy.

Q3: Can this be used for non-circular patterns?
A: No, this calculator is specifically for circular bolt patterns. Other patterns require different calculation methods.

Q4: What's the minimum number of bolts this works for?
A: The formula works for any number of bolts ≥3, though 4+ is more common in practical applications.

Q5: How does bolt size affect the calculation?
A: Bolt size doesn't affect BCD calculation, as we measure between bolt hole centers, not the bolts themselves.