cadquery implementation of a basic pulley

pulley.png

pulley.py

# Creates a pulley model 

import cadquery as cq
from Helpers import show

# Pulley Dimensions (mm)
radius = 20.0
width = 3  # contact area (not including wall thickness)
wall_height = 1.0
wall_width = 1.0

hole_radius = 3.175
key_intrusion = 0.92

# Pulley Base
pulley_half = cq.Workplane("XY") \
    .circle(radius + wall_height).extrude(wall_width) \
    .faces(">Z").workplane() \
    .circle(radius).extrude(width / 2.0)

# Hole
pulley_half = pulley_half.faces(">Z").workplane() \
    .moveTo(hole_radius - key_intrusion, hole_radius) \
    .lineTo(0.0, hole_radius) \
    .threePointArc(
        (-hole_radius, 0.0), (0.0, -hole_radius)
    ) \
    .lineTo(hole_radius - key_intrusion, -hole_radius) \
    .close() \
    .cutThruAll()

# Mirror half to create full pulley
pulley = pulley_half.translate((0, 0, 0))  # copy
pulley = pulley.union(
    pulley.translate((0, 0, 0)).mirror(
        'XY', basePointVector=(0, 0, wall_width + (width / 2.0))
    ),
)

show(pulley_half, (204, 204, 204, 0.0))
show(pulley, (204, 204, 204, 0.8))

Run using cadquery.

I recommend you run in FreeCAD with the cadquery-freecad-module (which is what the cadquery docs will tell you, so just follow those)

pulley_half is designed to be milled twice, then glued together