Ball screw repair, installed and aligned
Cavco repairs and replaces ball screws at the machine, and puts the axis back right afterwards. Backlash, lost position and a screw that has started to growl are usually the screw, its thrust bearings or the nut, and often more than one of them. We find which, fit the screw or a rebuilt one, set the preload, and align the assembly to the ways, so the axis holds position again instead of the new screw wearing in the old way.
What a ball screw fault feels like
The screw is the last thing most shops suspect, because the machine still runs. It is the first thing to check when an axis stops holding position, and the check is a measurement, not a teardown.
- Felt at the handwheel, seen as a step on a reversal. Usually the nut or the thrust bearings, sometimes the screw where it has worn most.
- The axis stops short or long, and the error changes along the travel. A worn screw, or bearings letting the screw float.
- A growl or a rumble that follows the axis. Bearings first, a damaged ball track second.
- A bent screw, a cracked nut, or bearings that took the hit. The alignment to the ways has usually moved as well.
- Preload set too high on a screw that was replaced, or a nut binding on a screw it was not aligned to.
- The axis overshoots and corrects. Backlash the control cannot compensate, or a coupling and bearing set that has gone loose.
The screw is half the job. The axis is the other half
A screw can be sent away and reground, and for a big one that is the right money. What no screw shop can do is what happens afterwards. The bearings go back preloaded, the nut goes back aligned to the ways, the axis is measured along its travel, and the control’s compensation is reset to the new figure. Skip that and the new screw wears the way the old one did. We do the whole axis, at your plant or at ours, and you get the numbers.
When the ways under the screw are worn too, the screw alone is a short fix. That is where this page meets rebuilding and alignment, and we say so before the work starts.
Ball screw repair by machine
The screw is the same idea on every machine. Where it fails, and what has to be put right around it, is not.
- Ball screw repair on Okamoto and Harig surface grinders is nearly always the table screw and its thrust bearings, and it shows up as a feed that steps or a table that will not hold its increment. The screw and bearings come out, the assembly goes back preloaded and aligned to the table ways, and the feed is checked along the whole stroke.
- Ball screw repair on Bridgeport mills means the table and saddle screws and nuts, and on a machine that has been working hard, the saddle ways beneath them. A new screw on worn ways repeats the backlash within the year, so we look at both.
- Ball screw repair on Mori Seiki and other CNC lathes is the X and Z axis screws, their thrust bearing packs and the couplings, most often after a crash or a long life on one part. The screw goes back preloaded, aligned to the ways, and the control's backlash compensation is reset to the new figure.
- Ball screw repair on Bullard vertical turret lathes is the rail and head screws, big enough that regrinding the screw pays, with new bearings and nut, and the head realigned to the table when the assembly goes back.
- Ball screw repair on Hardinge lathes is the cross slide and carriage screws, and it is usually part of a rebuild, because the machine has come apart for the ways at the same time.
- Ball screw repair on Fuji automatic lathe slides is a screw, nut and bearing set in a small space, with the slide realigned so the machine holds its cycle again.
Fitting ball screws to a machine that never had them is a retrofit, on our mechanical retrofitting page. A screw that failed alongside a drive or a control fault belongs with CNC machine repair, where the electrical side is covered. Finding which of the symptoms above is the screw and which is something else is diagnostics.
Questions we get
- Backlash you can feel at the handwheel or see in a reversal mark on the part. Position that drifts, so the axis stops short or long of where it was sent. A growl or a rumble that follows the axis rather than the spindle. Any of those points at the screw assembly, and the next question is which part of it. We measure the axis before we take anything apart, so the answer is a number and not a guess.
- Often the thrust bearings at the end of the screw before the screw itself. They take the load on every reversal, and when they go the symptoms look like a worn screw. A worn nut gives backlash with a screw that measures fine. A worn screw shows as backlash that changes along the travel. We check all three, because replacing the screw under bad bearings buys a few months.
- A screw with local wear can be reground and fitted with a new nut. A screw worn along its length, or bent, gets replaced. Bearings are replaced, never reused. We say which before the work starts, and we say when a rebuilt screw is the better money than a new one.
- The screw goes in with its bearings preloaded to specification and the nut aligned to the ways, so the screw is not fighting the slide. Then the axis is checked for backlash and position along its travel, and the control's compensation is reset where the machine has one. A rebuilt screw bolted back in against the old alignment wears out early, which is the part of the job the mail-in shops cannot do.
- Most of it, yes. On a machine that travels, the shop is faster. On a machine that does not, we do the work at your plant. Either way the axis is measured at the end, and you get the figures.
- Yes. Ball screws and nuts in place of acme screws, sized and preloaded for the machine, on ways put right first. That is a retrofit rather than a repair, and it has its own page.
- Okamoto and Harig surface grinders, Bridgeport mills, Mori Seiki and other CNC lathes, Bullard vertical turret lathes, Hardinge and American Pacemaker lathes, and the slides on Fuji automatics. If yours is not on the list, ask.
Reviewed September 2026 by Cavco Machine Tool Rebuilding, LLC.
Tell us which axis and what it is doing
Call, or send the machine and what you are seeing. We answer the same day.