When asked to produce a series of large diameter circular sheet metal components, I decided that a trepanning tool was required. I found this design from Hemingway kits. I then milled and turned accordingly to produce this tool, which worked reasonably to produce the parts required. If I were making this again, I would have made sure to use soft jaws in the 4 jaw chuck, when making the body and replaced the supplied stock that was only just large enough for the final dimensions with a larger stock piece to allow for machining of the body for a better surface finish.