Not Really A Dovetail Cutter

I need to cut a slot that is 0.5" wide at the top, and 0.728" wide. and 0.086" tall.  But square inside, not a dovetail.  What is it called?  Thanks to my knowledgeable readers: T-slot cutter.  I should have recognized this from the T-slots on the mill.

Dimensions chart:  What I need is throat diameter 0.5"; headspace depth .0086"; throat depth .59"; headspace width .728".  The closest match seems to be .375" T-slot bolt.  Still a bit deeper headspace depth than I want.  Perhaps I can put a piece of aluminum .284" thick in the bottom of the headspace to make up the difference.   (Probably just use a .25" thick piece as a start.)  This does not have a T-nut in the headspace; I need to bolt something down from the side.

Actually building an entire finder scope bracket is looking faster than finding a T-slot cutter this oddball size.  The dovetail required is 1.364" at bottom, 1.215" at top, .376" high.  A little trig should tell me what angle I need to put the tilting table at to create that slope.

It turns out that strange dovetail isn't that strange.  It is used on Synta and Vixen scopes, so I can buy off the shelf.  Whew!