Holes

Holes cuts every selected circle, either drilled with a drill or bored with a helix with an endmill. Select the circles (a whole layer is fine: other shapes are skipped with a note), then Holes (ribbon, OPERATION). Circles drawn in Chipload count, and so do imported circles, including ones drawn as two half arcs.

The tool decides how:

Drilling

• The drill feeds straight down at the hole’s centre.
• Pecks (optional): it drills that many mm, rapids up to clear the chips, rapids back down to 0.5 mm above the bottom, and drills on.
• End depth is the depth of the drill’s point. The full diameter ends a little higher, about 0.3 × the diameter for a 118° point.
• Plain moves: the holes are written as plain G0/G1 moves, not canned cycles, so they run the same on every controller and the checker reads them. The checker allows exactly one kind of rapid below the stock top: straight back into the hole just drilled.

Helical boring

• The path: the endmill goes down a helix at the hole’s wall, at most step per turn per turn and never steeper than the ramp angle. Then it cuts one level circle at the bottom, for a flat floor and a clean wall.
• Size: the hole comes out at its drawn size.
• Any endmill: the helix never plunges, so a tool that isn’t centre-cutting is fine.
• Too small: a hole must be larger than the tool, by at least a tenth of the tool’s diameter. Smaller holes are skipped, with a note.
• Larger holes: more than twice the tool’s diameter, the helix cuts a ring and leaves a core.
  • In a through hole, the core comes loose at the last turn, with a note. Hold it down, or use a pocket.
  • A blind hole that would leave a core standing is refused: use a pocket.

Order

Holes are cut nearest first, from where the tool is. Where the Holes operation sits in the list decides whether holes come before or after the profiles.

In the file

"type": "holes" in the project file. Lengths are in mm, feeds in mm/min, angles in radians.