I have an old lathe with a Maxi-Grip 2000 chuck (c.1995). Instead of a scroll, it has a rotating barrel which opens and closes the jaws using half-circular levers. It has jammed in the open position and I cannot remember which way to turn the barrel to unjam and close the jaws. Can any senior wood turner remember this chuck and help? Is it a "normal" thread or left-handed?