CNC millability_ tracing vectors to test for millability

I’m wondering if there is a good way to test vectors for millability. Of course this process can be done manually for relatively simple shapes. And, it would need to take into account bit size since an infinitely small bit can reach any small pockets. Just as an example, this is the shape that made me wonder.

Hi Josh -What is millability in this case? Minimum radius of curvature?


In this case I’d like to know:

  1. How small a bit I would need to use in order to mill the vectors as drawn- no additional radii?
  2. If there are parts of the curve that are too tight with a given bit size, which parts?

Thanks for your reply.

What you can do, as a sort of ‘by hand’ method, is turn on the CurvatureGraph adjust the scale to 100 (as a start, then the graph has a height that corresponds to the radius of curvature in current model units). That may give you the information you need. You can also use the Radius command to measure specific locations.


This is not so simple.

Cylindrical cutters must have a certain thickness, otherwise it will break during milling.
There are no special options for sharpness…
Only cutter minimum thickness shall prevail…
Is uninteresting to come to a thickness of 0.1 mm, is unlikely to work…
Milling is not recommended here, there are other better methods.

Working with conical cutters is a different situation.
Here are functions in milling software (if present): “area clearance” and “thinning corners”(similar to v-bit carving).
In many situations, cleanup of corners is possible with a pointed cutter.
Decisive here are “depth” and “side angle”.

Best regards

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Hi Eddi,
Thanks for your response. I am very aware of how the CNC process works; I’m also aware of re-machining with a smaller cutter if there are particular areas that need to be cleaned-up. In this case, I’m looking for a way to easily identify spots that cannot be completely milled (without adding a radius) with a given cutter size. If there is no great way to do that in Rhino, no problem. That’s a suitable response as well.

Thanks again,

Hie Josh,
A few ways we have in < Rhino > This can by automated with Rhinoscript.
Example for cylindrical …(conical must be calculated by depth and side angle).

Offset with cutter radius and Offset back.

Copy original / Paste and Fillet Corners (but only if everywhere are sharp corners)
If Radius to big, you see a message in Command “Some segments were not filleted”

Best regards

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Super useful. Thanks a lot.