Bearing repair is not a new concept, nor has it changed a great deal over the years—and that's good news. Repairing damaged bearings is a precise science that has been fine-tuned over time through careful and gradual enhancements to provide superior results.

Just as new designs and technologies improve bearings, growing expertise and technology of bearing repair continues to increase the reliability and performance of reconditioned bearings, keeping it an economical alternative to purchasing new bearings (see chart below).

Knowing and understanding the value of bearing repair means knowing what repair can do, when to use it, and where to get it done.

Bearing design takes into account the use and application of the bearing and establishes an appropriate prediction for service and fatigue life. No matter who the manufacturer is, bearings often deviate from these expectations due to factors such as contamination, inadequate lubrication, and misalignment.

When a bearing is damaged, the entire machine of which it is a part suffers. Conventional practice suggests that a damaged bearing should be scrapped and replaced. The growing popularity of bearing repair has helped companies understand its value by providing an efficient and cost-effective way to resolve the problem.

Bearings often can be returned to original specification for less time and money than purchasing new ones. A quality repair and reconditioning program can result in significant savings compared to discarding and replacing bearings. Depending on the scope of the work, bearing repair can save as much as 50 percent to 90 percent of the cost of purchasing a new bearing. Beyond the cost, repairs often save time compared to ordering replacement bearings, reducing costly downtime.

Another value-added service of bearing repair is using damage analysis as a tool to identify difficult conditions and prevent future problems.

Although it offers many benefits, reconditioning is not always the best option for a damaged bearing. The challenge of properly utilizing bearing repair services is determining if and when a bearing needs repair, and deciding which options are the best economical and long-term decision.

Visual inspection serves as the first step in deciding if a bearing needs repair. Careful review of additional criteria assists in determining the need for repair, such as:

• Is the bearing nearing or has it exceeded its suggested life expectancy?
• Have operating temperatures exceeded 200°F?
• Has the bearing been exposed to excessive vibration?
• Has the bearing been subjected to sudden changes in lubrication or temperature?

Early detection of a problem through routine checks can spare companies' unnecessary downtime and expense and help to capitalize on the capabilities and benefits of bearing repair.

Once a bearing is damaged, it should undergo a rigorous process to determine if it is a candidate for repair.

Bearings to be repaired should be thoroughly cleaned. Next, and the most critical step, is a detailed inspection on 100 percent of the bearing. Inspection begins with a careful review for major damages such as fractures, significant spalling, and bluing due to excessive heat. Any evidence of these usually results in scrapping the bearing.

If the bearing passes the first stage of inspection, it should undergo further review. This step serves to reveal a mode of damage, assessment of damage, and the scope of repair. The degree of bearing repair typically fits into three types.

Type I reconditioning is used for minor trouble spots and includes polishing, resetting of internal clearances, and spot grinding of any small surface defects to prevent further damage.

Type II repair is for bearings with more extensive damage. This level involves major procedures such as regrinding of raceways, new spacers, and polishing of the bore and cup OD. The regrinding of raceways will necessitate the manufacture of oversize rollers to maintain bearing geometry and clearance.

Type III remanufacturing takes Type II repair one step further by replacing one or more of the major components of the bearing that are not repairable.

These levels of repair have tradition-ally been suited for bearings with a minimum bore size of 8 in. However, reclamation service can be done for bearings as small as 3-in. OD.

Turnaround time on reconditioning and repairs can be as short as 2 to 4 weeks, depending on the needed repairs. Companies utilizing bearing repair should always request a complete quote when requesting any type of repair service.

It is important to have any bearing repair performed by properly trained and experienced personnel, because unnecessary repairs can lead to additional damage and limited bearing life. Common reconditioning mistakes include:

• Improper roller polishing that creates flat spots
• Excessive deep spot grinding
• Mixing of preset components

In addition to expertise, proper equipment is required not only to fix the problem, but also to ensure all damage has been reviewed and addressed. Magnifying glasses and proper lighting and measuring equipment are essential to perform thorough inspections and repairs.

This article originally appeared in the This article originally appeared in the Jan. 2004 issue of PLANT ENGINEERING, a sister publication to INDUSTRIAL DISTRIBUTION. For additional information on bearing repair services, visit www.timken.com/industrialservices.