This mounts a dial indicator (Mitutoyo 2046S) to my hobby CNC (Genmitsu PROVerXL 4030) without having to remove the spindle.  I'm aware this a strange combo of brands.  The plan is to use it to level the bed to the XY gantry and I wanted data exactly underneath the spindle for the mapping.

There are two versions, one for a .125in (1/8in) collet and another for .250 (1/4in).  

The small one is not too rigid at the neck, but it doesn't need to be since there should never be side-load.  The 1/4in version is untested, but is for folks who have done the Dewalt spindle upgrade.  Of course this works for non Genmitsu too.

I printed in PC with 6 wall loops.