A customer sent me a video last month. The screw was spinning on a test stand, and you could hear it—a rising whine that got worse as the RPM climbed. By the time the motor hit around 1800 RPM, the whole assembly was shaking hard enough that he didn't want to run it anymore.

He asked me if the screw was defective.

I asked him three questions instead.

What's the unsupported length? What support blocks are on each end? And how fast are you trying to run it?

His answers were: about 1100mm between supports, BK12 on the fixed end and BF12 on the floating end, and he wanted 2500 RPM so he could hit 25 m/min with a 10mm lead.

That right there told me the screw was probably fine. The problem was that the support arrangement and the operating speed didn't match.

This is one of the most common issues I run into when people order ball screws for CNC machines. The diameter is right. The lead is right. But the screw still doesn't run well, and nobody can figure out why.

It's almost never the