One more (maybe crazy) idea.

If you really need a flat bottom, then drill the mortise 3/8" extra
deep. Mill some stock to 1/2" square. Cut 3/8 wafers and pound them
into the mortise with a dao o glue underneath.

On Mar 17, 9:55 am, "David" cosmosatnointerbaunspamdotcom wrote:
Thank you all for your responses.

I have never used a mortise machine before and didn't know what to exprect.

I'll be using a sharp chisel to clean the ring out of each mortise.

David.