Hi KVOM
The pawl plates are slightly shorter than needed to allow for an adjusting screw to bear on the end so fine adjustment can be made to bring the tool slot to correct height, once set it should remain in position.
The load on the plates is when the spindle lock is off and the tool plate revolved to another position, the toolplate is turned back to the plate and the spindle lock applied, although the cutting action of the tool is trying to push the pawl into the plate the force on the plate is reduced by the spindle lock.
You are thinking where is the lock, sorry it does not show so well in the pictures, if you look at the shot where the main block is being bored, the 1/2" brass rod being held in position by a single bolt clamp acts as the spindle lock when completed, it is partly in the bore so has a segment cut that matches the spindle OD, this is cut at the centre and acts as the locking mechanism, I will post another picture to show the detail. This type of locking arrangement works very well and releases without problems when the locking nut/screw is released. This is equal to and likely a more positive lock than a stepper/DC motor reversing at less than full rated voltage.
Thanks for your interest.
Rgds, Emgee