Hi Bill, Its more involved that that. The lever operates a stirrup lever that locks the lower topslide to a central annulus with a 45 degree surface which pulls the disc upwards on a semi circular surface on the front of the lower slide. I t also pulls the lower face of the topslide into close solid contact with the cross slide surface and lifts the tee bars into contact with the underside of the tee slots.
The result is a very solid lock with a slight pressure from the locking lever. This is my own design I first made about 1976. I have written it up in the Model engineers workshop mag and tried to get people to adopt it because it works so well and changes the way the lathe can be operated. If you interested I can send a more detailed description.
