Types of Thrust Roller Bearings

Thrust roller bearings support heavy axial loads and are tolerant to misalignment. They are available in single-row forms and require little axial space.

The most common causes of bearing failure are contamination, misalignment and overloading. Contaminants can be airborne dust, dirt, sand, water and chemicals. Proper lubrication can reduce contamination and misalignment.

Needle Roller Bearings

Needle roller thrust bearings support high axial loads in one direction and allow the use of a thinner section than other types of thrust bearings. They are easy to fit and offer good shock resistance.

Their axial installation height is limited by the diameter of the needle rollers and cage, which makes them suitable for small spaces. They also have excellent vibration damping characteristics and a high axial load capacity.

Needle bearings require a minimum of maintenance, and their life can be extended by keeping them clean, using precision-grade locking nuts and washers, and maintaining proper lubrication. The three most common causes of bearing failure are contaminants, misalignment and overloading.

Drawn cup needle roller bearings have an outer shell that serves as the outer-ring raceway, which is accurately drawn and does not need machining. This reduces assembly costs and increases the bearing’s load carrying capacity. It can support axial loads in either direction as well as radial loads.

Cylindrical Roller Bearings

Cylindrical roller thrust bearings can only support axial loads. With a simple design, they can provide high axial load capacity and rigidity and are typically used in the main shafts of precision machine tools. These bearings come with a choice of cage designs - pressed steel or machined brass and are available in different sizes to suit the application and client needs.

These bearings can also withstand incidental thrust loads (loads that act parallel to the rotational axis) in addition to their radial load capacity. They can be designated as single-row cylindrical or double-row cylindrical depending on their mounting orientation. Single-row bearings are designated by the single-letter nomenclature NU, N, NN, and NUP, and can be specified as nonlocating or locating.

With line contact between the rollers and raceway, this type of bearing has a very good radial load capability; however, its axial load capacity is lower than that of ball bearings. This bearing is often employed in running wheels and crane rope sheaves.

Spherical Roller Bearings

Spherical roller thrust bearings contain friction-reducing rolling elements (usually cylindrical rollers) supported in an inner ring with a spherical raceway and an outer ring with two inclined races. These designs permit the bearing to tolerate misalignment between the shaft and housing while allowing for high speeds with steady acceleration and deceleration.

Available in TT and TTF types, these bearings are designed to sustain axial loads and can accommodate slight deviations in shaft misalignment that occur during operation. These are self-aligning bearings based on their curvature, and are unaffected by mounting errors and shaft deflection. They can also withstand heavy loads, even at low to medium speed.

These bearings are typically used in applications with demanding conditions and require oil lubrication to operate at optimal levels. In addition, they are often subject to contaminants like airborne dust, dirt, and sand that can cause denting of the rolling elements and raceways and increase frictional loads. The use of proper filtration and clean work areas can help reduce contamination issues.

Thrust Bearings

Thrust Bearings are a type of rolling-element bearing that supports an axial load in one direction. They have a single thrust washer or raceway that the rolling elements ride along and support rotating parts to reduce vibration and misalignment. They are usually designed to be self-aligning and can handle radial loads as well.

Thrust bearings can be made more robust and operate at higher speeds with a special design known as “Hand Scraping”. The process involves using a tool to scrape the thrust shoe for flatness, which creates shallow isolated pockets in the babbitt surface. This improves lubrication at start-up and shutdown by providing a more consistent flow of oil to critical contact points.

Other factors that can affect the life of your thrust bearing include contaminants, misalignment and overloading. Contaminations like airborne dust, dirt, sand and water can cause premature bearing failure and wear and tear. Operating conditions like temperature and fluid pressure are also important to consider when choosing the right thrust bearing for your application.