Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5026388. T handle for holding a tap up to 3/8". There's a #7 hole (0.2010") that was intended for a 1/4-20 tap to thread and use a set screw to hold the taps in place. This is a work-in-process and I've included the Solidworks file for anyone that wants it.