Hi Andrei, actually I guess you shouldn't form triangles on the end because the side surfaces are not flat and if you just draw in a straight line it may not hug the surface well enough to cut it.

So instead of a straight line here:




Put in instead a 3 point plane surface (Draw solid > Plane > 3pts), snapped on to these 3 points:




So your cutting object would be the chamfer fragment and then one of those 3 point planes on either side.

- Michael