Understanding Bolt Circle Calculations
A bolt circle is a circular pattern of bolt holes, commonly used in engineering for flanges, wheels, or other mechanical components. This calculator determines the X and Y coordinates of each bolt hole based on the bolt circle diameter (BCD), number of bolts, and starting angle.
Coordinates are calculated using X = BCD/2 * cos(angle) and Y = BCD/2 * sin(angle), where angles are evenly spaced around the circle (360°/number of bolts). The starting angle offsets the first bolt position.
Bolt Circle Examples
| Bolts | BCD (in) | Start Angle (°) | Description | Coordinates |
|---|---|---|---|---|
| 4 | 5 | 0 | 4 bolts, 5 in BCD | (2.5, 0), (0, 2.5), (-2.5, 0), (0, -2.5) |
| 6 | 10 | 0 | 6 bolts, 10 in BCD | (5, 0), (2.5, 4.33), (-2.5, 4.33), (-5, 0), (-2.5, -4.33), (2.5, -4.33) |
| 8 | 8 | 22.5 | 8 bolts, 8 in BCD | (2.83, 2.83), (0, 4), (-2.83, 2.83), (-4, 0), (-2.83, -2.83), (0, -4), (2.83, -2.83), (4, 0) |
How to Use the Bolt Circle Calculator
- Enter the bolt circle diameter (BCD) in inches or millimeters.
- Specify the number of bolts (e.g., 4, 6, 8).
- Input the starting angle in degrees (typically 0° for standard patterns).
- Select the unit (inches or millimeters).
- Click "Calculate Bolt Coordinates" to see the X and Y coordinates for each bolt hole.
Bolt Circle Visualization
Bolt hole positions for a 5 in BCD with 6 bolts (0° start angle).
Frequently Asked Questions
What is a bolt circle diameter (BCD)?
The BCD is the diameter of the circle passing through the center of each bolt hole in a circular pattern.
Why is the starting angle important?
The starting angle determines the position of the first bolt, useful for aligning patterns with specific orientations.