Hello,
I am not clear what's your issue? You can probably use "Chamfer feature" API to create custom chamfer with "two distances" or "distance and angle" option. Or you can create an extrude feature with the sketch to cut the "Polygon" body to get custom "chamfer" as well.
http://help.autodesk.com/view/fusion360/ENU/?guid=GUID-f0eae304-aaca-4ced-b8c0-3b679d7c1f3d
Thanks,
Marshal
I need my chamfer features, don't fusion "ChamferFeatures". All I need calculate point A or B.