I've had my King 1236 for 2 months now and I'm working through some issues / setup with it. Today I decided to use the 4 jaw chuck and see it is stamped "Max 1350 RPM". The 3 jaw is stamped max 2145 RPM. According to the decals on the lathe the top speed is 1500 RPM. The Grizzly site indicates the G4003 top speed is 1400 RPM. I am guessing the top speeds for both machines are actually the same but I don't know for sure. For you G4003 owners, can anyone tell me what speed their 4 jaw is rated for. Seems odd that the lathe would come with a chuck that can't be used in all speeds.