Bolt Circle / Hole Coordinates
Generate an equally spaced bolt-circle pattern and its hole coordinates from a known BCD.
0° places Hole 1 on +X (3 o'clock). Pattern center defaults to X0 Y0.
Pattern
Graphic is a geometric sanity check. Coordinate values below are the controlling results.
Pattern Information
Hole Coordinates
| Hole | Angle | X | Y |
|---|
Absolute coordinates include the selected pattern-center offset.
Chord Geometry
Find chord length, included angle, BCD, or chord across hole positions.
Chord length is the straight-line center-to-center distance between two points on the same bolt circle.
Calculation Rules
Hole coordinates are calculated from the bolt-circle radius using standard Cartesian geometry. A start angle of 0° is on +X; positive angular progression is counter-clockwise unless clockwise direction is selected.
Chord geometry uses the standard circle relationship Chord = BCD × sin(Angle ÷ 2). The same relationship is rearranged to recover included angle or BCD. For equally spaced patterns, the included angle is 360° × hole separation ÷ total holes.
The Bolt Circle tool reports adjacent-hole chord as pattern information. The Chord Geometry tool handles reverse BCD calculations and chord measurements across multiple hole positions.
Incremental coordinates show movement from the pattern center to Hole 1, then from each hole to the next hole in the selected direction.