I would like to cut a hole that is wider on the bottom of the sheet than at the top. So for example using a 60mm holesaw gets me the same diameter on both sides of a 21mm thick sheet. How can I get 60mm on the one side and 70mm or so on the other side, with a flush straight angled surface between the two sides (around 45 degrees).
Doing some googling, I came across beveling but I cant seem to find any large enough bevel or countersink bits. The purpose will be for a spherical object to sit nearly flush on the cut section and slightly protrude on the visible top/front side of the sheet (I have attached a basic image trying to show what I am trying to accomplish).
Any advise appreciated but ideally using the machinery I currently have (drill, table and circular saw, jig saw and grinder).
Please also forgive my lack of terminology here as I am new to this.