Thrust bearings

01

Choose the thrust bearing type for the loads and alignment

SKF's 51320 datasheet states that single direction thrust ball bearings accommodate axial loads in one direction and must not be subjected to any radial load; they are separable, and the shaft washers have a ground bore that enables an interference fit. [1] Kinex adds that the washers have flat seating surfaces that must be supported to spread load evenly over the balls, that double direction thrust ball bearings carry axial load both ways with a central shaft washer between two housing washers, and that thrust ball bearings are not suitable for misalignment of the shaft and housing washers. Boundary dimensions follow ISO 104. [3] [4]

Kinex describes cylindrical roller thrust bearings as rigid, with high load capacity and resistance to impact loads, carrying axial forces only; they may be single- or double-row, and the cage and roller assembly (K), shaft washer (WS) and housing washer (GS) can be bought separately so that machine parts form the raceways. Cages are polyamide 66 (TN) or brass (M), and precision grades P6 and P5 are available above normal P0. [4]

Spherical roller thrust bearings, per Kinex, carry high axial load plus radial load only while Fr ≤ 0.55 Fa, and their spherical housing raceway allows misalignment of 2° (292 series), 2°30′ (293) and 3° (294) under Pa ≤ 0.1 Ca; oil lubrication is necessary except at very low speeds. [4] SKF states its spherical roller thrust bearings accommodate very heavy axial and considerable radial loads and have the highest load rating of all its thrust bearings; the 29424 E (120 × 250 × 78 mm) lists C 1,370 kN, C0 3,450 kN, a 2,600 r/min limiting speed and 16.5 kg. [2]

Editorial calculation: against the SKF 51320 thrust ball bearing (100 mm bore, C 225 kN), the 29424 E spherical roller thrust bearing (120 mm bore) has 1370 ÷ 225 ≈ 6.1 times the dynamic rating and 3450 ÷ 570 ≈ 6.1 times the static rating. [1] [2]

Give the supplier the axial load (one or both directions), any radial load, shock loads, speed, lubricant and method, operating temperature, shaft and housing dimensions, misalignment, required life, cage material, tolerance class, whether separate washers or cage assemblies are needed, and quantity.

02

Check load ratings, speed and minimum axial load

SKF's 51320 single direction thrust ball bearing (bore 100 mm, outside diameter 170 mm, height 55 mm) lists a basic dynamic load rating of 225 kN, basic static load rating of 570 kN, fatigue load limit of 18.3 kN, reference speed of 1,400 r/min, limiting speed of 1,900 r/min, minimum load factor A of 1.9, a sheet metal cage and a mass of 4.95 kg. [1] Kinex's 51320 of the same 100 × 170 × 55 mm size lists Cr 236.5 kN, Cor 595.0 kN, Cu 23.31 kN, limiting speeds of 800 min⁻¹ with grease and 1,200 min⁻¹ with oil, and 5.100 kg. [3]

Kinex states that ratings follow ISO 281 (dynamic) and ISO 76 (static), that L10 is the life reached by 90% of a bearing group with exponent p = 3 for ball bearings, and that its listed limiting speeds assume L10h ≥ 100 000 h, normal operating conditions and cooling. For thrust ball and cylindrical roller thrust bearings the equivalent loads are Pa = Fa and Poa = Fa; for spherical roller thrust bearings Pa = Fa + 1.2 Fr and P0a = Fa + 2.7 Fr. [4]

Kinex warns that at higher speeds thrust balls can slide between the raceways under centrifugal force if Fa falls below a minimum set by the maximum speed and the factor M in its tables, and that the minimum load must be secured, for example with springs, when one bearing of a pair is relieved. Cylindrical roller thrust bearings also need a minimum load from a shaft nut or springs, and for spherical roller thrust bearings Kinex gives Famin = 0.00125 C0a. [3] [4]

Editorial calculation: with L10 = (C/P)³ million revolutions for ball bearings, the SKF 51320 under a pure axial load of 50 kN gives (225 ÷ 50)³ ≈ 91 million revolutions, about 91,000,000 ÷ (1,000 × 60) ≈ 1,519 hours at 1,000 r/min; applying Kinex's Famin = 0.00125 C0a to the 29424 E gives 0.00125 × 3,450 ≈ 4.3 kN. [4] [1] [2]

Editorial note: makers state speed limits on different bases (SKF reference and limiting speeds; Kinex grease and oil limiting speeds), so compare suppliers' figures only on the same basis and lubrication.

03

Compare what suppliers offer

No manufacturer record has been reviewed for this product yet.

When requesting quotations, ask each supplier for the datasheet with C, C0, fatigue load limit, speed ratings and minimum load factor, the cage and tolerance class, and the recommended shaft and housing fits.

04

Trace the bearing parts

This is a functional reference built from the sources cited; it is not one maker's design.

05

Fill the specification fields with values for your design

A thrust bearing quotation needs values for your design. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

06

Send the loads, speed and mounting data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Loads: [axial; direction; radial; shock]
Speed: [r/min; duty cycle]
Lubrication: [grease or oil; temperature]
Mounting: [shaft; housing; misalignment]
Bearing: [type; designation; cage; tolerance class]
Life: [hours]
Quantity: [units]

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