Key Factors to KnowWhen you’re choosing ball or roller bearings for your next project, there are three key factors to keep in mind: contact angle, preload, and system rigidity. 1. Contact Angle This is the line of contact along which the ball bearing touches the raceways of the assembly. This angle is determined by the thrust loading and radial play. Ideally, the contact angle should be 15°—this is the optimal balance between axial and radial capacity and rigidity. To increase the axial rigidity, some systems have a contact angle of 25°. No matter which angle works best for your system, it’s essential to choose the bearings that operate best at the given angle. 2. Preload Preload is a force that holds the raceway and rolling element surfaces under pressure. It’s a constant elastic compressive force that stops the parts from moving in an uncontrolled manner —either axially or radially—even when they’re under load. The right bearings will tolerate this additional force without breakage. 3. System Rigidity Machine tools generate several different forces that ball and roller bearings need to be able to account for. Factors such as housing stiffness and bearing stiffness determine the machine’s system rigidity and ability to produce consistently precise results.
Maintenance and CareAll bearings have a pre-determined bearing life, or a maximum number of rotations the bearing can undergo. These rotations impact the inner rings, outer rings, and rolling elements with constant load, which leads to inevitable wear. Factors that can lead to excessive wear and shorten the effective lifespan of the bearings include:
- Inefficient or full contact seals. The more contact a bearing has with a seal (such as a full contact seal) or the less calibrated a seal is, the more wear the bearing will undergo. This can wear the sealing element as well as the bearing.
- High speeds or speed changes. If the bearing is operating at excess speeds, the friction can quickly wear through a bearing. Also, excess speeds can increase sliding speed, which causes uneven wear. If the operation speed changes too quickly, that will increase the slip and wear.
- Poor environmental conditions. Dirt, dust, and other foreign particles can scratch the ball bearing’s surface and cause wear. The presence of water can also corrode the surface, leading to poor performance and a shortened lifespan.
- Grease storage. Always keep grease tins closed when not in use and keep the containers in a separate storage environment with stable temperatures. We recommend not using grease that’s more than three years old.
- Grease application. Once the bearings have been cleaned and completely dried, apply grease over the balls and rings. Be sure an equal amount of grease gets between the balls in the inner ring. To ensure the grease is as clean as possible, always apply it with clean spatulas or with clean plastic syringes for precise applications.