How to determine where bit will start plunging and where it will retract?

[Rlpotts (Ron Potts)]

I have a couple reasons to figure this out.
One is to plunge a keyhole bit off the work, cut a cut a groove around the inside a rectangle then exits out of the wood before retracting.
The other is to plunge a surfacing bit off the wood before it starts to move.
I don’t know how to tell the machine where to start and end the cut.

[WillAdams (William Adams (Carbide 3D))]

For a keyhole we have a specific toolpath:

Carbide Create V7 Question- Keyhole toolpath

I’ve seen more and more references to people trying to work out how to make keyholes in CC. We’d be open to adding that as a toolpath in V7 so I’d like a little feedback. To simplify, we’d probably define the location with a circle, like the drilling toolpath, and then you’d define how tall you’d like the keyhole to be, and what direction from the center, Y+, Y-, X+, X-. We’d probably implement the toolpath as a plunge, line to the end and back, then a retract. We would not offer to “expand”…

Where a toolpath begins/ends is determined by the program, except for contour toolpaths associated with unjoined/open geometry — they will begin/end at the begin/end points.

You can verify where those points will be in the 3D preview:

[Tod1d (Tod (with 1 'd'))]

There are no CC toolpaths that will start off the workpiece. The only engage types are Plunge or Ramp on part which ramps directly above the first pass in the path.

If you want to start off the part, draw in your own toolpath & use the contour / no-offset option

To cut a T-Slot around the inside of a circular pocket, draw in the path you want.
This one arcs into the material, cuts around the circle, and arcs out.
It’s an open vector that overlaps itself on the engage & retract.
To build it you have to stretch the vector so it doesn’t overlap, join it, then move it back.

To tell which is the engage & retract, the engage plunge is green, and the retract is red

I would rather have my T-cutter climb cutting, so I’ll mirror the vector horizontally