The ST 5 is a mill spindle with MT 4 taper. It fits early 2015 Mill Turn machines. it is an excellent choice for any DIY mill project. It is designed for speeds up to 7000 RPM. Accepts sealed double row angular contact ball bearings, 5207 2RS1 on the tool end and 5206 2RS1 on the pulley end. Where the pulley fits it has an 8 MM X 20 MM key way for the key. The end is threaded 25 MM X 1.5 for a retaining nut. There is a 15 MM hole through the spindle for the drawbar and a 40 MM flat milled on the tool end for use with a wrench to hold the spindle while loosening and tightening the drawbar.
Please refer to the sketch for general dimensions.