Thank you for the reply. I likely did not articulate my question well, what confuses me is the ability to select power to the rack instead of the lead screw by flipping a lever on the apron. Powering the carriage with the lead screw makes scenes to me for accuracy. But when the rack is powered through the gear box the motion is jumpy and inconsistent. This all makes me wonder why some thing more than hand power on the rack might be needed. Thanks
Eric