One way is to make several circles one inside the other spaced about half the bits width and then assign them as center line cuts at different depths getting deeper as you reached the smallest center hole. It would not be a perfect cone and would have a stepped look to it, but it just may work.

 

if you use a conical bit it would be smooth
in fact if you swap to a countersink bit you can just do it in one cut, just calculate the correct depth.

 

That's too easy! I don't know why I didn't think of doing it that way, for some reason I had it in my head to do it the hard way round.

 

lol. working towards tool change capability I suppose, so you can set up tool profiles, and then select which profile gets used for a cut. one day in the future....

meanwhile, using table top as Z zero is under test, and last night I think I got IJ format arcs working, they are more accurate than R format so should solve the small arc problem with dogbones, though exploding all the dogbone arcs is a total fix for that anyway.

btw chamfering edges is very easy with a 90 degree countersink tool, just decide on 2 things
width of the chamfer , ie width in from the edge of the material
effective cutting width of the chamfer tool, equal or less than previous slotting tool

so, say we have 4mm material and we have already cut the outlines with a 3.2mm bit.
lets have a 0.5mm chamfer
lets use a 3mm tool diameter (this is some point up the side of the chamfer tool where the diameter is 3mm)
do not use the tip, the teeth are very small at the tip and do not work effectively.

depth of cut is half the effective diameter, 3/2 = 1.5 so set overcut% to 1.5/4*100 = 37.5%

now we need so set toolbit diameter, which is given by
diam = effectivediam - (2* chamferwidth)
diam = 3- (2x 0.5) = 2
so set tool diameter to 2mm

now draw in new inside and outside cutlines and generate the gcode for this tool.
result might look like this (in OpenSCAM)


using a 60 degree taper bit is left as an excersize for the user.

 

Thanks David!

Sounds like the tool profiles maybe in the future of SketchUcam!