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How do I draw holes on a bolt circle (PCD) in AutoCAD?

Type "draw 8 holes of 9 mm on a 120 mm PCD, first hole at the top". cadssistant computes the eight positions at 45° intervals on a 60 mm radius starting at 90° and creates the circles in one batch. Add "centred at 250,400" for a coordinate, or "ask me for the centre" to snap it in the drawing through AutoCAD's own point prompt; with neither it uses the centre of your current view and says so. Say "with centre marks" or "on layer HOLES" and it adds those. The same routine in AutoLISP is a repeat loop over polar, shown below.

Checked 2026-10-30

What you typeCommand: CADSSISTANT

draw 8 holes of 9 mm on a 120 mm PCD, first hole at the top

Paste it into the palette, or pick it from the recipes inside the chat.

What cadssistant does

  1. Fixes the centre: the coordinate you gave, the point you snap to when you say "ask me for the centre" (AutoCAD's own point prompt; Esc cancels), or the centre of the current view, stated as an assumption.
  2. Computes the positions: 360° ÷ 8 apart on a radius of PCD ÷ 2, starting at 90° for "first hole at the top".
  3. Creates the eight circles of diameter 9 in one step and replies with the positions it used.

The same task in AutoLISP

(progn
  (setq c (getpoint "\nCentre of the bolt circle: ")
        n 8 pcd 120.0 d 9.0 start (* 0.5 pi) i 0)
  (repeat n
    (entmake (list '(0 . "CIRCLE")
                   (cons 10 (polar c (+ start (* i (/ (* 2 pi) n))) (/ pcd 2.0)))
                   (cons 40 (/ d 2.0))))
    (setq i (1+ i)))
  n)

Eight 9 mm holes on a 120 mm PCD, first at the top. Change n, pcd, d and start.

Good to know

  • Angles are counter-clockwise from the X axis, as in AutoCAD. "First hole at the top" is 90°.

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