Sorry, no poster comes with this...
Finally bought a 1" length of 6061 tubing with a 2.625 ID from Speedy Metals. Bored it out to 2.675 or so then faced it to .625 long. Milled a pocket, center drilled, ran a #25 in, followed with a #11 part way. Tapped 10x24, over to the bandsaw, cut about 1/16th out (two cuts). Tightened it up, nice and tight. Removed the collar, milled @ 1" flat for a mounting plate for the bottom scale mount.
Yes, it would have been possible to take a .625" thick square of 6061 and bore/turn it, but that's a heckuva lot of chips.
The base for the scale had me flummoxed. I dislike drilling freehand into cast iron. The current thought- I sawed off a length of .250 thick6061 the same length as the scale's display, milled two bores in about 3mm deep for some rare earth magnets, then drilled and counterbored two holes for the scale mounting screws.
Perhaps, when all is done, the magnets will hold the scale tight enough to the cast iron mill head. Waiting on a 3/4" 2 flute mill to get here.11/16ths just do not work (18mm dia magnets)