I made this handle for rotating the lathe spindle manually during threading (with  a tap or die), single point threading,  parting off, and other lathe operations.  

The  handle includes a slitted shaft, with an expanding taper at the end, which fits into the 20 mm spindle bore.  In use, the shaft slides easily into the bore and is secured  by tightening the fastener. 

SAFETY NOTICE  

This handle in intended for manual operation.  If  the lathe is inadvertently powered the rotating handle could cause physical harm to the operator. 

However, if care is used and the operator remains clear, the handle has been balanced and can rotate to 1,000 rpm with minimum vibration.