Hurricane Turning Tools, HTC100/125 Woodturning Chuck Threaded Insert Adapter, 1 1/4 x 8-Inch TPI Thread type : 1 1/4" x 8 TPI These adapters will fit the HTC100 4" Chuck and the massive HTC125 5" Chuck. For Powermatic 3520, 3520A, 3520B, 4224, 4224A, Robust Lathes (and possibly others).