A spindle crank is an enormous help for specific operations.  If you make items such as optical adapters or other items having large diameter, fine, short thread sections this will allow much safer thread cutting without the anxiety of destroying a part by damaging a shoulder from a fractional second delay disengaging the half-nuts.  This handle has the additional safety feature of being disengaged from the shaft when not being turned by hand.  This is a feature found on many mills equipped with power table feed.  If the lathe is accidentally turned on without removing the handle, it does not present the hazard of an immediately spinning object.  (Handle is also attractive and nicely counterbalanced.)

Order Spindle Crank Kit - $39                               Order Spindle Crank Machined & Assembled - $99