Centering microscope

Hi all. Ive always been keen on the idea of a centering microscope (optical centre punch also on to do list) but given my needs are not high and their prices its clear ill probably never aquire one. BUT I have to ask, has anyone ever thought about making one using a S/H low magnification microsope? Good quality old scopes are a dime a dozen can be had for under $20 - $30 in the U.S. An objective/eyepiece combo with 10X would do nicely. Challenging part would attaching a post to fit in collet and align along optical axis. Even more chellenging would be the cross hairs being in focus with the workpiece.



Thoughts?



Simon