Yeah, that's right.
In most unfinished industrial screw gearboxes, the crown is not made all in bronze but a centrifuged bronze shell band is reported on a cast iron hub which in its outer diameter has grooves and "dents" to stop the bronze crown and avoid slipping or detaching.
in your design these reliefs are obtained at the center of the cast iron hub, in the drawing that attach are double and alternate; solution adopted by many gear manufacturers.
This solution allows an economic saving because the amount of bronze (more expensive than cast iron) is in reduced quantity and performs the function of antifriction material, unlike the cast iron that in contact with the steel screw could grip.
another advantage is that of the greater resistance of the cast iron hub as it is on it that burdens the task of transmitting the bike to the shaft through tongue.View attachment 62745
