I don't like this. Too easy to crack through and zingoes the front half.
That was my first reaction when I looked at one of the chucks that came with my 9” Utilathe.
Turns out the chuck was super high quality, made in Japan. The flange bore was a very close fit to the spindle nose flat. The locking collar was made from steel - also a close fit to the flange OD. A single SHCS locked it.
I did some testing: screwed the chuck onto the spindle without bottoming it out against the rear register (about a quarter turn shy, so there was a visible gap). Tightened the locking collar. Took a foot long adjustable spanner and grabbed one of the jaws. Selected highest spindle speed. Blocked the motor by pinching it with wood. Now pulled hard on the spanner. Every time the motor belt slipped. The chuck never spun on the spindle - either forward or backwards. That was proof enough for me that this clamping system works and it is safe to run the lathe in reverse under normal operating conditions.
The close fit of the components, the elasticity of the CI and the strength of the steel collar seem to work well together in this case.
The chuck / collar were exactly like
@dfloen has modified his.
@Susquatch , totally agree with the stress concentration point where the saw cuts end. One could try and drill radial holes first and then have the saw cuts end in them. Would go a long way to mitigate the potential… OTOH, the Japanese engineers did not think it was necessary…