Spindle Lubrication

 

Spindle bearings are lubricated to reduce wear and friction. A very thin layer of lubricant sits between the moving elements separating them from each other. If this film is not sufficient enough to properly lubricate the bearing premature failure will occur.

Spindle lubrication can be split into two categories grease and oil.

Grease lubricated spindles usually do not require additional attention after they are rebuilt. We place a metered amount of grease into the bearing during the assembly process that lasts for the life of the bearing. Some spindle manufacturers have developed spindles that are equipped with grease injection systems. These systems inject a metered amount of grease into the bearing at specific time intervals. This method is not common.

Oil lubrication has many more applications:

Oil mist: This is one of the most common oil delivery systems but it is being phased out due to environmental issues. This delivery system uses a venture to atomize oil and send it to the spindle in an air stream. Oil mist systems can be identified by the tell tail ?bubble? sight glass that shows the drops of oil. Counting how many drops per minute come from the hooked tube tells you the amount of lubrication your spindle is receiving. This is a fairly fail safe system of delivery as the oil the bearing needs ?wets out? on the rolling elements and the rest exhausts out of the spindle through the drains. Unfortunately it is inefficient and the extra atomized oil ends up in the shop air.

Oil Injection: This system replaces the oil mist system. This system can be identified by a high pressure oil pump that pushes the oil to a mixing block. The mixing block has multiple ports that feed the spindle bearings typically one port per bearing. The improvements over oil mist are that the oil remains in liquid form, the oil is metered very well, much less oil is required for the same applications and the systems are very reliable. Companies are currently working on monitoring systems that can since oil in the line. This will ensure your spindle is being properly lubricated.

Oil bath: This is very old technology that basically submerges the bearings in oil. This has virtually been phased out in spindle applications.

Hydrostatic/hydrodynamic: This method, used primarily in grinding applications, ?floats? the spindle shaft on a constant film of oil. The oil can be pressurized by a pump or moved by the shaft. This style of lubrication gives very tight running accuracies but low load capabilities. The spindle failures normally seen are contamination in the oil causing deterioration of the bearing performance and overloading that causes the spindle shaft to contact the outer raceway.