A bone cylinder also has a barbell shape but with the two ends round, resulting in a kinematic four-point interface to the V block. The undercut section in both the barbell and bone configurations can be used for knurling, center screws, adjustment and lock-down mechanisms without affecting the cylinder to V block interface. The interface length should not be reduced to where the clamping load might damage either component. Clamping is the application of a force load to a cylinder located in a V block. A spring or flexure loading mechanism determines the location of the cylinder in the V block.
Axial location is usually the result of clamping friction at the interface.
An axial hard stop could also determine axial location prior to clamping.