How Does the 51100 Series Down-Thrust Bearing Handle Vertical Loads?
The 51100 series down-thrust bearing is a single-direction thrust ball bearing designed to accommodate axial loads in one direction. With a bore diameter of 10mm, outer diameter of 24mm, and height of 9mm, it is a compact unit that fits into tight vertical shaft arrangements. The bearing consists of two hardened steel washers (shaft and housing washers) and a ball and cage assembly. The shaft washer is mounted with an interference fit on the shaft, while the housing washer is mounted with a clearance fit in the housing. This configuration allows the bearing to support axial loads up to 12.5kN dynamically and 17kN statically. The 51100 series is manufactured to P0 tolerance class (ABEC 1) as standard, with tighter classes available on request. The pressed steel cage ensures uniform ball spacing and reduces friction during operation. This bearing is not designed for radial loads; it requires separate radial support.
Typical applications for the 51100 down-thrust bearing include vertical pumps, gearbox input shafts, crane hooks, and automotive steering columns. In a vertical pump, the bearing carries the axial thrust generated by the impeller, preventing shaft displacement and maintaining proper impeller clearance. For gearbox input shafts, it supports the axial reaction forces from helical gears, ensuring smooth power transmission. The 10mm bore size is particularly suited for small to medium-sized equipment where space is limited but axial loads are significant. Unlike larger thrust bearings, the 51100 series offers a balance between load capacity and compactness, making it ideal for portable or benchtop machinery. Its limiting speed of 6300rpm with oil lubrication allows it to be used in moderately high-speed applications, though grease lubrication reduces this to 4500rpm.
Compared to other thrust bearings in the 51100 series, such as the 51101 (12mm bore) or 51102 (15mm bore), the 51100 offers a lower profile and lighter weight, which is advantageous in applications where every gram counts. However, it has a lower load capacity than its larger counterparts. The 51100 is also available with a spherical housing washer (51100V) for applications where misalignment cannot be avoided. This variant can accommodate up to 2 degrees of misalignment, reducing edge loading and extending bearing life. For harsh environments, a stainless steel version (51100-2RS) with contact seals is available, providing protection against dust and moisture. The standard 51100 bearing is lubricated with lithium grease and can operate in temperatures from -30°C to 120°C.
- Dynamic load rating of 12.5kN and static load rating of 17kN for reliable axial support in vertical shafts.
- Pressed steel cage reduces friction and ensures even ball spacing, contributing to low noise and vibration.
- Available in P0 (ABEC 1) tolerance class as standard, with P6 (ABEC 3) and P5 (ABEC 5) on request for precision applications.
- Optional stainless steel version with contact seals for washdown or dusty environments.
