How to check whether G33 would hit machine limits?

Sure. Going from one speed to another can't go instantly. It seems that usually the machine catches up with the desired position at some later point - perhaps by going faster and then slowing down again. Looking closely at my test-objects I can even see that. At some times it simply fails to do that, though. Subsequent commands are then executed at the wrong position. Under which conditions would that happen?

torotil wrote: Sure. Going from one speed to another can't go instantly. It seems that usually the machine catches up with the desired position at some later point

I don't have much experience with G33. I have used G76 extensively, and my impression is that that is allowed to lag behind the "ideal" position but retracts at the right point. The amount of lag would vary with spindle speed, so there is a recommendation in the documentation not to alter the spindle speed between threading passes.