Hand knobs GN 6335.1 with protruding hub have important advantages:

The face of the hub is exactly square to the bore and is made of steel to prevent edge breakage.

Specification

Hand knob
Plastic
Duroplast (Phenolic PF)
Black, shiny finish

Hub insert
Steel, zinc plated, blue passivated finish

RoHS

On request

Special bores and threads larger than listed
Other modifications such as cross holes and set screw holes
Special stud variations, either drilled and pinned or glued into place