A stepped shaft with three coaxial cylinders stacked: bottom section 20mm diameter × 10mm tall, middle section 14mm diameter × 20mm tall, top section 10mm diameter × 15mm tall.
import cadquery as cq result = ( cq.Workplane("XY") .circle(10).extrude(10) .faces(">Z").workplane().circle(7).extrude(20) .faces(">Z").workplane().circle(5).extrude(15) )