This is a holder for a dial indicator with a 8mm stem holder.
The indicator is held horizontal and at center height, and moreover fixed on the cross-slide, which makes setting a 4-jaw an easy task.

You may want to print the T-nuts flat on the printer bed, they might be hard to print otherwise.

Glue the countersunk screws in the T-nuts, and glue the M3 nuts in the printed thumbwheels (hex hole). Glue the pan head screw in the printed thumbscrew (round hole)

With the indicator in this position and on the cross-slide you can setup a 4-jaw or precisely indicate a taper since the indicator is on the slide (so you can crank it both on X and Z)

I also enclose my Solidworks 2014 source files.