Screw on lathe chuck security.

[tonyfoale]

Alan,

It won't stop the problem with screw cutting to a shoulder but this is a tip to remove drive to the chuck quickly and reduce rotating inertia, literally at the touch of a button.
Air conditioning pumps from a car have a nice electro/magnetic clutch. Apply 12v and the clutch is engaged, remove it and it is free. A/C repair shops usually have dud pumps. They are easy to gut and place in the lathe drive chain. Torque capacity seems quite high but I have no figures nor have I measured that, I have just used them. I haven't done it yet but you could fit a second one as a chuck brake. Connect them such that when one is on the other is off. Almost instant stop, but screw on chucks will need your retainer or watch out for flying chucks.