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In the decision-making process on how best to return a failed spindle into service, Ed Zitney of SKF Services answers four frequently asked questions that are applicable to any operation considering spindle remanufacture.

Posted: June 22, 2011


In the decision-making process on how best to return a failed spindle into service, here are four frequently asked questions that are applicable to any operation considering spindle remanufacture.

Machine tool spindles, in all their designs and sizes, represent complex systems integrating dozens of components critical to machine tool performance. They are routinely used to rotate cutting tools, grinding wheels, or parts to be machined in applications ranging from milling, drilling, and boring to grinding, cutting, and sawing. When a spindle goes down, two questions naturally arise: Can the spindle be remanufactured? Should we simply replace the system outright?

In typical repair cases, customers will initially pose a variety of basic questions to assist them in the decision-making process on how best to return a failed spindle into service. Here are four of the more frequently asked questions (with answers) applicable to any operation considering spindle remanufacture:

Are you sure that you can successfully repair my “XYZ” spindle? The thinking behind this inquiry is that a customer effectively wants to know for certain that a particular spindle is a prime candidate for repair over replacement. This is a daunting challenge, because there are thousands of makes and models of spindles and a quick response to this question may not come easily at the outset.

The question can best be answered with as complete a spindle profile as possible. Helpful information includes the spindle manufacturer (not always the same as the machine), the model number, maximum rpm, horsepower, tool nose configuration, and drive type (belt, gear, coupled, or integral motor). In addition, does the spindle have manual or automatic tool change? Can the spindle bearings be identified from the OEM manual?

When information such as this is available, the remanufacturer will be more fully equipped with highly useful knowledge to help answer the “can-you-repair” question.

How much will it cost to repair the spindle? With the critical information supplied, a fairly accurate “ballpark” price – but not a firm one initially – can usually be provided. Even with the best information from the customer, it is typically impossible to price-quote confidently without a hands-on, full inspection of the damaged spindle. This should come as no surprise.

What is the turnaround time for the spindle repair? Based on the initial information from the customer, a best/worst case delivery timeline can generally be developed. But the bottom line is that until the spindle is completely disassembled, cleaned, and inspected thoroughly, an absolute turnaround time will be elusive. If a customer supplies accurate information about their spindle and the equipment appears in reasonably good shape, then a delivery date will likely be more on target. If the spindle is in bad shape or has unseen damage internally, an evaluation by a repair technician will be necessary to determine a true timeline for return to service.

Can an exchange spindle be provided? With thousands of different types of spindles being used in the field, it is usually only by chance that an exact replacement spindle will be carried in stock to match a particular unit. However, sometimes an alternative model – or even a new and better spindle – can make an exchange possible.

One of the questions most often asked – with universal appeal – refers both to failed spindles and those in service: How can I get more life from my spindle?

Understanding the way that each spindle is used in its daily operation is critical to realizing extended spindle lifetime. More often than not, spindles must perform in harsh environments that often lead to potential internal contamination, especially of the bearings, and ultimate failure. Contaminants can include any foreign substances from coolant and condensation to grinding swarf, chips, and debris from material being machined.

When contamination is present, modifications to the spindle, especially with regard to the sealing system, can be implemented to mitigate problems in the future and promote extended service life. In some applications a spindle may be run too hard or be forced to operate where it was never intended according to its original specifications. Design changes can be made in these situations to reconfigure and tailor spindle setup in line with the specific application for enhanced service life.

Besides these top four questions, when considering a specialist for repair it is important to always begin the process by asking pertinent questions about the remanufacturer’s expertise. Spindle repair service providers should be able to demonstrate a history of specialized experience with all spindle brands, types, and applications. They should maintain a consistent focus on detail and quality, and possess knowledge about the universe of potential spindle defects and their root causes.

When all of these credentials are established to your satisfaction, you will be well on your way to a successful outcome.

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