cw is usefull if you use a tap or a die in conjunction with the tailstock to apply pressure, use a centre for a tap, faced off MT sleeve for a die, tap wrench or die holder resting on the bed like a dog, reverse to get said tap or die off for 2nd and 3rd cuts. Not one for small threads though. Also you dont get nice clean sharp threads come to think of it. But it has its purpose. if you try it beware of the wrench flipping around and getting you under the chin when you put it in reverse.