Contact surfaces in a linear guide

2024-04-09

Ball bushings are an early version of linear guides. They use rows of balls that roll against a hardened shaft to transfer load. This type of guide is still used in many applications today. But—it has a weak spot.

The contact surface between the rounded shaft and the spherical ball is tiny, which results in very high pressure per unit area. Even though the surfaces are hardened, high loads can still leave grooves in the shaft.

Modern linear guides (also called rail guides) began taking over in the late ‘80s. They use a ball track that wraps around the ball more fully, creating a line contact rather than a point. This makes it possible to carry much higher loads—and is one of the reasons for their exceptional load capacity and long service life.

Linear guides come in various designs—some with 2, 4, or even 6 ball tracks.
Today, they are the most common type of linear guidance, used where precision, high load handling, and low maintenance are important.

You can watch a video on this with Carry Lindholm from Bosch Rexroth here: