When you first push a new linear guide by hand and hear a light “shh-shh" sound, it’s easy to worry that something is wrong. On the machine, the noise can feel even more obvious, especially in a quiet workshop.

The truth is: a ball-type linear guide will never be 100% silent. Steel balls rolling on hardened steel raceways will always create some mechanical sound. The key is to tell the difference between normal running noise and abnormal noise that needs attention.

In these situations, some sound is usually normal and does not mean the guide is defective:

• Dry hand-pushing without grease – When you move the block quickly without load and with very little lubricant, the metal-to-metal contact is more direct. A light, even “rustling" sound is expected.
• High preload or high-precision blocks – Blocks with higher preload are slightly tighter by design. They may feel heavier to push and a bit louder at the beginning, especially before running-in.
• Very quiet environment – On a test bench or in a silent room, you will notice sounds that are completely masked once the machine, motors and pumps are running.

As long as the movement feels smooth and consistent, without obvious sticking or sudden resistance, a light, even sound is usually acceptable.

If the noise is clearly louder than expected, or the block does not move smoothly, check these typical causes first:

• No grease or very little grease inside the block
• Grease that is too thick, too thin or not suitable for linear guides
• Old grease that has been sitting for a long time in storage or during transport

Effect: Increased friction, “dry" rolling feeling, more pronounced metal sound, sometimes combined with slight vibration.

Linear guides are very sensitive to how they are mounted:

• The rail mounting surface is not level or has machining steps
• Parallel rails are not aligned correctly
• Screws are tightened unevenly (some over-tightened, some loose)

Effect: The block is forced to deform to follow the twisted rail. One side of the raceway carries more load, which increases noise and can cause tight spots when the block passes certain positions.

• Dust, metal chips, sand or other particles entering the raceway
• Rail not cleaned before installation
• Block removed and re-installed in a dirty environment

Effect: Grinding-like noise, scratch feeling, or intermittent “click" sounds. This needs to be handled quickly to avoid permanent damage to the raceway.

Sometimes you might find that:

From the same order, some blocks are very smooth and quiet, but one or two are obviously louder.

This may indicate:

• One block was affected by impact during transport
• Internal preload or clearance is slightly out of tolerance
• A rolling element or raceway spot is defective

In this case, it’s important to compare rails and blocks from the same batch and mark the noisy ones.

Before judging a noisy linear guide as “bad quality", you can follow this quick checklist. Many issues can be solved on-site:

• Use a linear guide or ball screw grease (NLGI #2 is common)
• Move the block slowly to distribute the grease along the full stroke
• Check the noise again after a few full strokes under light load

Often, the sound level drops noticeably after proper lubrication.

• Confirm the rail is mounted on a machined, flat reference surface
• If there are two rails, check the parallelism according to the machine design
• Loosen and re-tighten the screws gradually and evenly, following the recommended torque

If noise appears only after installation but the loose rail feels smooth, the problem is usually related to the mounting condition.

• Take two or three blocks from the same shipment
• Move them on the same rail, under the same conditions
• Note which ones are clearly noisier or feel “scratchy"

If only one or two blocks are much louder or not smooth, mark them. This information is very helpful for after-sales analysis.

If, after lubrication and installation checks, the noise is still abnormal:

1. Take clear photos of the rail, block and installation area
2. Record a short video of the movement and sound
3. Note the model, length, preload class and working conditions

Send this information to your supplier or after-sales team. If the product does not match the description or there is a real defect, a replacement block or other solution can normally be arranged quickly.

• A linear guide will never be completely silent, especially when pushed dry by hand.
• Light, even steel-ball rolling sound is normal.
• Obvious grinding noise, tight spots or strong vibration are not normal and should be checked.
• In many cases, correct lubrication and proper installation reduce noise significantly.
• If units from the same batch behave very differently, mark the problematic ones and contact after-sales support for replacement.

With a simple inspection and a bit of troubleshooting, you can often turn a “noisy and not smooth" first impression into a stable, reliable linear motion system—without unnecessary returns or downtime.