Realigning the head of a mill/drill after raising or lowering is real 
nuisance, as anyone who has one will tell you. I added an attachment 
to my m/d which helps solve that problem.

I mounted a vertical bar parallel to the column to be used as a dial
indicator reference point. A dial indicator is mounted to the side of
the head and is set to zero before loosening the head. The head clamps
are then released, the head is raised or lowered, the head is then
rotated to bring the indicator back to zero, and the clamps retightened.

The bar is 1 5/16" drill rod (something I had on hand) but 1" should
work OK too. The bottom mounting plate is 3/4" aluminum, the top bracket
is 5/8". I made a plug to go inside the top of the column to fasten the
top  bracket to. The inside of the column was only machined a half inch
deep so the plug is held in place with three screws through the top edge
of the column into the plug. The indicator is mounted to a 3/8" bolt 
through a hole in the bottom of the belt guard. One draw back is the belt 
guard cover can't be completely removed for speed changes. However the 
guard can be hung up one the top bracket while changing belt positions. 
Another option is to cut a gap in the guard to allow it to be removed.

It was also necessary to extend the crank shaft to clear the bar.

The pictures should answer most questions. If not, feel free to ask.

Bob Bachman

bobach@voyager.net