MichaelG:
Thanks for the link to the PM article describing the single tool slot version of the device mounted direct to the cross slide.
I see that the tool post was intended to be rotatable around its holding-down screw thus presenting the cutting tool either normal or parallel to the lathe axis. This apparently raised the question of the tool post’s resistance to unintended rotation and the suggestion of increasing the friction between it and the mounting surface with a fibre washer; another idea would be to substitute a stud and nut for the screw and interpose a thrust bearing between them.