I'm using a UC100 motion controller with your C11G breakout board to control a KBCC-125R DC motor driver for the spindle. Then the axis are Automation Technologies Nema 23 3 phase hybrid steppers with their KL-5080H controllers which are very accurate and fast!
The floating tap holder allows for a little over 1/4" of movement in either direction and it is made from hardened A2 tool steel. It uses two set screws from alternate directions to drive the square tang of the tap and one set screw on the top to hold a split steel drill bushing for the taps shaft OD. The two shoulder bolts slide in the grooves of the body to apply the necessary torque, the bottom one had to be ground to miss the saddle. The body is made from 1020 hot rolled steel that is cold gun blued to protect it from surface rust.