The two most important concerns when installing a linear slide are bearing parallelism.

• A. Lubrication Type
• B. Surface Finish
• C. Material Hardness
• D. Bearing Parallelism

Answer: (D)

When installing a linear slide, how the bearings ride along the rail determines how smoothly and accurately the system will move. The key point is keeping the bearing blocks parallel to the rail so they stay in uniform contact along the whole length. If the blocks are not parallel, they can tilt as the carriage moves, causing one side to bear more load than the other. This leads to binding, higher friction, uneven wear, loss of stiffness, and reduced straightness and accuracy. Achieving true bearing parallelism ensures uniform preload and consistent contact, so motion remains smooth and predictable across the travel range. In practice, you verify parallelism with precise measurements during installation and adjust with shims or mounting tolerances until the carriages move freely without binding across the full length. While lubrication, surface finish, and material hardness matter for wear over time, they can’t compensate for misalignment—the parallelism of the bearings to the rail is what makes the slide perform reliably.