This is a 1 1/2" (38mm) woodscrew chuck for the Precision Pro pen lathe. It screws directly onto the spindle thread having first removed the collet nut. It is a great choice for drawer knobs, finials and other smaller projects of this type. The small screw fitted as standard to the chuck has a core diameter of approximately 4mm and a 19mm tapered thread. Other thread sizes are available.