create a sketch on the front plane,
revolve using bottom line,
create a new sketch on the face shown,
create this sketch, circle dimensions from gearing equations from Machine Design books....
on the same face create a sketch for a helix, and create a helix with following dimensions..., values from equations...
create a cut sweep,,
create a circular pattern of sweep
on front plane create a sketch, circle, and extrude it,
create a new plane
create a mirror about the new plane,,
create a cut extrude, for shaft and key...
and fillets to soften up the edges, very very tiny fillets...