The Farr Miters Touch is a very nice fixture for mitering chainstays on a vertical or horizontal mill. I used it on a small horizontal mill and it worked great. You can bolt the base plate to the mill table and bolt the fixture to the base plate for perfect alignment every time.
It comes with a bonus dummy axle holder for Sputnik axles.
I use a different fixture now so this one is up for sale. Asking $700 + shipping.