Handling Spindle Bearings Properly

While spindle bearings are generally fatigue endurable they must be handled with care. Small impacts, burrs or nicks can affect performance and lifespan. Proper handling, installation and storage is critical.

Coolant, high heat metal chips and grinding swarf can enter the bearing and contaminate the grease causing excess heat and premature failure. Air purge systems can decrease contamination issues.

Preventive Maintenance

Like the pillars of a building, bearings support all loads projected onto a rotating shaft. With so much pressure, they are subject to wear that can cause problems when ignored.

The good news is, you can avoid some of the most common spindle issues with a few simple preventive maintenance techniques. Taking steps to protect the environment, monitor air quality and properly lubricate the equipment will help reduce contamination that can damage a spindle.

In addition, a spindle can be monitored with vibration and temperature sensors that warn of problems before the bearing reaches failure temperatures. Taking advantage of these tools and incorporating them into a predictive maintenance schedule can make all the difference in spindle longevity. A well-established schedule partnered with proper day-to-day operating practices will ensure that your spindles last as long as possible.

Installation

Taking the time to remove everything carefully and in the proper order ensures that components are returned to their correct positions. Even a small impact or burr on any part can significantly reduce performance and lifespan.

Ensure that the headstock bearing housing is clean and free of rust before installing the new bearing. If a re-used bearing is installed while the spindle assembly is hot, it can cause brinelling (cracking of the bearing raceways).

When installing a new bearing, adjust the vice to allow the inner race to rest on its jaws without touching the shaft. Use a clean steel drift and tap the bearing gently until it is securely seated. A rounded face on the drift eliminates pressure point dings and helps prevent stress on the bearing.

Storage

The lubricant in capped bearings loses effectiveness over time. During storage, the grease deteriorates, condensation forms and separation occurs between base oil and thickening agent. Unless a spindle is actively cooled with liquid, the lubricant will eventually separate from the metal and form an acidic substance that causes corrosion.

It’s best to store a spindle in an area that is dry and not subject to drastic temperature changes. An air-conditioned room is ideal.

If a spindle is stored for an extended period of time, it should be run regularly to redistribute the lubricant and change the initial placement of the rolling elements in raceways. Performing the break-in procedure in this manner will also prevent any heat or vibration issues when the spindle is reinstalled in your machine. Most experienced repair facilities include a break-in process for every new and rebuilt spindle they service. The spindle should be started at 10% of its maximum speed and monitored for 30 minutes. If the temperature at the bearing housing does not remain consistently within an acceptable range, begin again starting at a lower RPM.

Operation

Using air hoses to blow coolant away from equipment can force particles into spindle bearings and damage them. The use of a purging seal system is recommended to reduce contamination and prevent premature bearing failure.

Alternatively, you can install a manual lubrication system on your machine tool to dispense small amounts of grease to the bearings whenever needed. This is a cost-effective option that will provide consistent lubrication, but it does require a diligent maintenance schedule and workers must remember to add the correct amount of grease at the right time.

Automatic lubrication systems are more complex, but they will automatically apply the appropriate amount of lubricant to your spindle bearings at regular intervals. These systems can be programmed to dispense the lubricant at the correct times and are typically controlled by a pump.