Advice on toolholders

[Rabs]

If the key is sprung it would be designed to act at a point to stop overtightening as well as aligning the thread to start at a specific it would only engage at a point beyond just beyond correct torque when milling, presumably you release it to with the chuck to undo otherwise it would engage and lock once on each rotation.

I think m_c's point is that the toolholder can't be tight against the key and the taper at the same time - it has to hit one of them first. If you want that to the key to stop over tightening, then itwon't be tight on the taper. If it isn't tight on the taper then the tool will wobble. Thanks for taking the time to help though - there might well be something there related to keyways. I'll give it some thought.

Big lathes, the tapers never turn against each other. They're secured using either bolts, or a retaining nut.

The only small lathes I've seen with screw on chucks, use locating registers, not tapers.

Ok, that makes sense. I suppose the smaller angle the taper the more prone it will be to locking because the larger the radial force is for a given axial bolt tension. That also explains why a lathe chuck with a flat register (which I suppose can be considered as a 180 degree 'taper') is much less prone to locking.

If it makes any difference this is a small machine with a 1/2hp spindle motor.