Embodiments of the invention include an orthopedic milling machine for preparing a glenoid bone. The milling machine uses a hub and a sleeve. The hub includes reliefs arranged to cut or mill the bone and the sleeve couples to the hub to transfer rotational motion to the hub. The hub has an axial bore sized to receive an orthopedic guide pin. The hub also has a lateral passage slot that allows the hub to move laterally towards the guide pin in order to place the guide pin within the axial bore.