Splicing linear guides

Published by Emelie Neckman, 2024-09-04

Rails are typically manufactured in lengths between 1–6 meters, depending on the type, size, and brand.

These are the standard mill lengths we stock and cut from based on your required lengths.

Most rails have pre-drilled mounting holes with fixed spacing—say, 60 mm for a certain size.

But what if you need a rail longer than a mill length?

Rails can be spliced—laid end-to-end—to achieve a longer stroke.

Here are a few things to consider:

The rails must be very close in terms of tolerances. Since a preloaded carriage has to move smoothly from one rail to the next, height and width mismatches must be minimal—we’re talking microns.

This can be achieved either by selecting matched rails or choosing a higher tolerance class.

The rail lengths should be selected so that the distance from the splice to the first mounting hole on each side is symmetrical—otherwise, things can go wrong.

How do you splice rails?

There are at least three common ways:

• 1. Sharp edges on both rail ends – best in dirty environments.
• 2. Chamfered ends – reduces wear on seals, more forgiving but creates dirt traps.
• 3. Chamfered tops only – helps seals while keeping sharp edges in ball tracks.

Keep in mind that total rail height tolerances are generally looser than ball track tolerances.

If a rail gets damaged:

1. In method 1, you should replace both sections.
2. In methods 2 and 3, it’s usually okay to replace just one.

With spliced rails, you can essentially build infinitely long tracks.

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