36 n MECHANICAL POWER TRANSMISSION June 2026 www.drivesncontrols.com Rack-and-pinion system delivers a long-range alternative to ballscrews Reekie Machining, based in Inchinnan in Renfrewshire, was established in 1947 to manufacture portable machining tools. Since then, the company has expanded its activities to provide on-site machining services. It specialises in CNC systems for in-situ machining. For one of its projects, Reekie needed to provide precise position control for a CNC machine over a distance of up to 4.5m. The machine is used to mill and machine parts for a company in the shipbuilding industry. The project demanded low levels of backlash and high levels of accuracy. The machine needed to be adjustable in length from 2–4.5m, allowing it to machine items such as large baseplates. This meant that a linear ballscrew drive would not be suitable. Backlash One possibility was to use a rack-and-pinion system in conjunction with planetary gearboxes. Reekie Machining had not configured its machines in this way before because of problems associated with backlash, but it had previously bought gearboxes for linear motion applications from Apex Dynamics, and decided to try a rack-and-pinion system from this supplier. The rack systems provide accurate movement and positioning, and operate at low noise levels. They are manufactured to meet Quality 4 standards, and are tooled in an underground location to control temperatures and ensure quality. The long-life rack systems can operate at high speeds with tight tolerances. Apex also supplied its AB planetary gearboxes to provide a full rack drive system capable of high-quality coordinated transmission. The helical planetary boxes contain gears hardened to 840 HV. A patented input bearing system ensures perfect concentricity to deliver high torque and efficiency, and low noise and backlash. Reekie has found that the rack-andpinion arrangement is producing the accuracy and low backlash that it needed for a precision finish. It is achieving positional accuracies of ±0.05mm over a range of 2–4.5m. The company is now looking at developing its own in-house machine using a similar design. CAD step models and other resources from Apex allowed Reekie Machining to incorporate the gearboxes and rack-andpinion system easily into its designs. “The project has now been completed and it has all gone well. The machine works and we got the accuracy we needed,” reports Reekie Machining’s managing director, David Reekie. “Using a rack drive system allows us to go a lot longer without compromising precision. We anticipate working with Apex Dynamics again in the future on different types of machines, as they provide the accuracy and low backlash that we need. n A Scottish machine-builder has changed from using ballscrew drives in a CNC machine to a rack-andpinion system to achieve high positional accuracies with low backlash over a distance of up to 4.5m. Reekie’s rack-and-pinion system is delivering low backlash and high accuracies for its CNC machine
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