A precision gear rack only performs as well as it is installed. Most positioning errors on long-axis machines come from poor rack joints and mounting surfaces rather than from the rack itself.

Prepare the mounting surface

Machine the mounting face and the reference shoulder to the required flatness and straightness. Clean all burrs and paint.

Joining racks

Use a joining gauge (a short rack segment) across each joint so that the pitch is continuous. Tighten the screws from the centre of each rack towards the ends, then ream and fit the dowel pins.

Setting backlash

Adjust the pinion so that the backlash is 0.03–0.08 mm for precision drives, checking at several points along the axis. Lubricate the teeth with grease or an automatic lubricator.