Bolt Circle Layout
Hole coordinates (X, Y) for a circle of N evenly spaced holes from a bolt-circle diameter, start angle, and center.
Example
You enter
- Bolt circle diameter (in) 8
- Number of holes 6
You get
- Radius (in) 4
- Spacing / chord 60
- Chord (in) 4
Details, formula, and sources
Hole coordinates (X, Y) for a circle of N evenly spaced holes from a bolt-circle diameter, start angle, and center, plus the angular spacing and adjacent center-to-center chord (first-principles circle-of-holes trigonometry).
R = dia/2; hole i at angle start + i*(360/N): x = cx + R*cos(angle), y = cy + R*sin(angle); angular spacing = 360/N; adjacent center-to-center chord = 2*R*sin(180/N).
Circle-of-holes (bolt-circle) layout - the standard hole-pattern coordinate geometry as in Machinery's Handbook (Industrial Press), by name; first-principles trigonometry.
Pure trigonometry, public; confirm the hole pattern, datum, and tolerance against the drawing before drilling.
Estimate. AHJ and licensed professional govern.
Field names used by the API: bolt_circle_dia_in, num_holes, radius_in, angular_spacing_deg, chord_in
- Even spacing the N holes are evenly spaced on one circle; for an unequal pattern enter each radius/angle directlycircle-of-holes geometry