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Tutorial Beginner ⏱ 8 minutes

Bolt-Hole Pattern

Create a 6-hole bolt-hole pattern on a 100mm pitch circle diameter — the standard method for flanges, mounting plates, and fixtures.

What You Will Build

Six 8mm diameter holes equally spaced on a 100mm PCD (50mm radius pitch circle). Suitable for M8 bolts on a standard flange.

Operators Used

Circle/Centre,R Points/On,C,N Circle/Centre,R
01

Define the Origin and Pitch Circle

Create the centre point and the pitch circle. The pitch circle defines where the hole centres will be placed.

P_origin = (0, 0) [flange centre] Circle/Centre, P_origin, R=50, 0 → C0: pitch circle, centre=(0,0), radius=50mm [PCD = 100mm]
The pitch circle (C0) is a reference circle. It will be used to place the hole centres but is not itself a hole.
02

Create Six Equally Spaced Hole Centres

Use Points/On,C,N to create 6 equally spaced points around the pitch circle. Starting at 0° places the first hole at the rightmost position.

Points/On, C0, N=6, Angle=0, 0 → P0 = (50, 0) [at 0°] → P1 = (25, 43.301) [at 60°] → P2 = (-25, 43.301) [at 120°] → P3 = (-50, 0) [at 180°] → P4 = (-25, -43.301) [at 240°] → P5 = (25, -43.301) [at 300°] Angular spacing = 360° / 6 = 60°
All 6 points created simultaneously. Each is assigned an individual point reference identifier.
03

Create the Six Holes

Create a circle at each hole centre point. For M8 bolts, use a clearance hole diameter of 8.5mm (radius 4.25mm).

Circle/Centre, P0, R=4.25, 0 → C1 [hole at 0°] Circle/Centre, P1, R=4.25, 0 → C2 [hole at 60°] Circle/Centre, P2, R=4.25, 0 → C3 [hole at 120°] Circle/Centre, P3, R=4.25, 0 → C4 [hole at 180°] Circle/Centre, P4, R=4.25, 0 → C5 [hole at 240°] Circle/Centre, P5, R=4.25, 0 → C6 [hole at 300°] All holes: diameter = 8.5mm (M8 clearance)
04

Clean Up Construction Geometry

Delete the construction points and optionally the pitch circle if it is not needed in the final drawing.

Edit → Clear All Points → P0-P5 all deleted → C1-C6 unchanged (baked geometry) Optional: Undo C0 if pitch circle not needed in final drawing Final geometry: C1, C2, C3, C4, C5, C6 [six 8.5mm diameter holes on 100mm PCD]
Points are construction-tier entities — deleting them does not affect the hole circles.
05

Verify the Pattern

Use Measure → Distance to verify the distance between adjacent hole centres. For a 6-hole pattern on 100mm PCD, adjacent hole spacing = 50mm.

Adjacent hole spacing = 2 × R × sin(π/N) = 2 × 50 × sin(30°) = 2 × 50 × 0.5 = 50mm Measure → Distance Click C1 centre, Click C2 centre → Distance: 50.000mm ✓
All adjacent hole centres should be exactly 50mm apart for a 6-hole pattern on 100mm PCD.

Tips & Best Practices

  • Use Points/On,C,N for any regular polygon or circular array — not just bolt holes.
  • For a 4-hole pattern, use N=4 with Angle=45 to place holes at 45°, 135°, 225°, 315°.
  • The pitch circle (C0) can be kept as a reference or deleted — it does not affect the holes.
  • Always verify hole spacing with Measure → Distance before generating CAM toolpaths.
  • For tapped holes, use the tap drill diameter, not the bolt diameter.

Operators Used in This Tutorial

Points/On,C,N

N Points on Circle

Creates N equally spaced points on a circle.
Circle/Centre,R

Circle by Centre and Radius

Creates a circle at a centre point with a given radius.
Point/On,C,Atangl

Point on Circle at Angle

Creates a single point at a specific angle on a circle.

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