The gripping pull-back action to actuate the collet chuck means the work piece will be moved slightly in the Z-Axis.
This is normally acceptable for first operation work and the work piece position can easily be determined with a facing cut.
The 5C and 16C collets have been designed with a long small nose diameter allowing for good clearance for tooling.
All collet closers are case hardened and ground optimising the rigidity, strength and durability.