Replacing a CNC Ball Screw

      When a CNC's ball screw fails, you can get an aftermarket part custom-built but is it worth the hassle? June 30, 2007

We recently found out that the ball screw for the table on our late 90's Komo router is shot and needs to be replaced. A new one from Komo can run $10,000 and I was wondering if anyone else has encountered this situation and if there are any other options, i.e. rebuilding the screw or purchasing it from an outside manufacturer?

Forum Responses
(CNC Forum)
From contributor J:
You need to find out what mm diameter it is, such as 40mm, 63mm, etc., and the pitch. Measure the overall length; most machine shops can machine the ends and you should be able to get one. Then you will have to have it checked with a laser for accuracy once installed and tensioned. Probably a Star, NSK or THK. Replace the ballnut at the same time. Some leadscrews have an extra set of leads you can use when the original wears out. That was what we used on the DMS routers.

From contributor C:
Seems pretty soon to have worn out a ball screw! We've got some 20+ year old machines that have run 2 and 3 shifts without significant wear on the screws. Obviously if it's bad, you're going to have to fix it, but I'd sure want to know what the cause of all that wear is and correct it before installing a new one.

There are companies that rebuild ball screws and can bring them back to original spec, assuming that they aren't too far gone. It's been many years since I've looked for that, so I can't give you any names, but I'm sure if you Google around a bit you'll find some. The question to ask with a rebuild is, can you stand the downtime required to remove it, ship it off, have it be in their shop for days or weeks, ship it back and then re-install it?

To buy a new one from a third party may save you some money but could be tricky. If it were me, I'd want to be able to go to the original manufacturer of the screw to be sure that I'm getting the exact same spec (pitch, diameter, etc.) as the original. Then you will need to supply them with specs for the additional machining such as bearing fits, supports, servo couplings and so on. If you don't get it all right, you may end up with a screw you can't use.

The advantage to a rebuilt unit or a new one from a third party is obviously the potential cost savings. The disadvantages are the time you will invest in the project, lost production time, and the risk that it won't go well.

The advantage to a new unit from Komo is that you know it will be the right part and will work as new or you don't pay for it until it does. The disadvantage is higher cost. In our case, we'd probably swallow hard and buy the new one from the machine tool manufacturer, in this case Komo. We'd lose more in lost engineering and production time than would be saved trying to source it ourselves.

In the end you'll have to make the call based on your level of in-house expertise, production needs and risk tolerance.

From contributor R:
How did you determine that the ball screw is bad? Did you do a backlash test? Have you tried adjusting the backlash in the ball nut? If it really is the ball screw, they can be remanufactured.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor B:
We recently had a 20 ft. long Ball Screw failure due to a crash on our Hein CNC Router. We were told two months lead time for a replacement unit. In a bind, we sent the old Ball Screw to Wedin International in Cadillac, Michigan and they repaired the entire unit in three working days! We have been running trouble free since re-installing it in a few months ago and we are very satisfied with our results.

Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?

Have you reviewed the related Knowledge Base areas below?
  • KnowledgeBase: Knowledge Base

  • KnowledgeBase: Computerization

  • KnowledgeBase: Computerization: CNC Machinery and Techniques

    Would you like to add information to this article? ... Click Here

    If you have a question regarding a Knowledge Base article, your best chance at uncovering an answer is to search the entire Knowledge Base for related articles or to post your question at the appropriate WOODWEB Forum. Before posting your message, be sure to
    review our Forum Guidelines.

    Questions entered in the Knowledge Base Article comment form will not generate responses! A list of WOODWEB Forums can be found at WOODWEB's Site Map.

    When you post your question at the Forum, be sure to include references to the Knowledge Base article that inspired your question. The more information you provide with your question, the better your chances are of receiving responses.

    Return to beginning of article.

    Refer a Friend || Read This Important Information || Site Map || Privacy Policy || Site User Agreement

    Letters, questions or comments? E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page.

    Contact us to discuss advertising or to report problems with this site.

    To report a problem, send an e-mail to our Webmaster

    Copyright © 1996-2019 - WOODWEB ® Inc.
    All rights reserved. No part of this publication may be reproduced in any manner without permission of the Editor.
    Review WOODWEB's Copyright Policy.

    The editors, writers, and staff at WOODWEB try to promote safe practices. What is safe for one woodworker under certain conditions may not be safe for others in different circumstances. Readers should undertake the use of materials and methods discussed at WOODWEB after considerate evaluation, and at their own risk.

    WOODWEB, Inc.
    335 Bedell Road
    Montrose, PA 18801

    Contact WOODWEB

  • WOODWEB - the leading resource for professional woodworkers

      Home » Knowledge Base » Knowledge Base Article