Linear guides – different solutions for referencing and locking against reference surfaces

Published by Emelie Neckman, 2024-10-01

How should you think about reference surfaces in your linear guide application? The first thing to consider is whether you have:

  • Significant lateral forces acting on the linear guide carriage
  • A need to fully utilize the accuracy of the linear guide

If the answer is yes to either of these, it’s a good idea to incorporate one or more reference surfaces into your design.

The most common approach is to guide one of the rails in your design using a reference edge—this gives you a fixed point for aligning the rest of the setup. This reference edge is usually milled into the machine frame when the mounting surface is machined. It’s also common to mill a reference surface into the plate that mounts onto the carriages on the guided rail.

This gives you a simple way to ensure straight installation. It also helps you align a parallel rail and a ballscrew more easily, extending the service life of your machine or equipment.

However, if you also have lateral loads acting in both directions on the linear guides, you’ll need to include a counterforce system that continuously presses the guided carriage or rail against the reference edge.

On the rail, you can:

  • Mill a groove that the rail fits into (only works for a few brands)
  • Mill a groove and use a pressure wedge to secure the rail (continuous support)
  • Use clamps that press against the rail using screws (point support)
  • Use a system with eccentric screws to press against the rail (point support)

On the carriage, you can:

  • Mill a groove and secure a pressure wedge
  • Use clamps pressed against the carriage with screws
  • Use eccentric screws to press against the carriage
  • Fix the carriage using cylindrical or tapered pins

In some applications with two parallel rails, both rails or both sets of carriages are guided. But be cautious—either one rail or one set of carriages should remain “free-floating.” The reason? Temperature changes can create internal stresses that cause increased wear. In tool machines, where temperature is stabilized with coolant, this isn’t an issue.

Here’s a video on the topic featuring Carry Lindholm from Bosch Rexroth: