Bearing Selection

Vocabulary flashcards covering key terms from the Bearing Selection lecture notes.

Bearing

A machine element that reduces friction between two mating surfaces and helps carry radial and axial loads.

Plain Bearings

Bearings with sliding contact, including metallic porous impregnated bearings and non-metallic dry bearings.

Metallic Porous Impregnated Bearings

Sintered metallic bearings impregnated with lubricant (oil or polymer) to reduce friction.

Non-metallic Plain-Dry Bearings

Bearings made from materials such as nylon, PTFE, and carbon that operate without continuous lubrication.

Hydrodynamic Fluid Film Bearing

A bearing in which a lubricant film keeps surfaces apart due to pressure generated by rotation; lubrication can be fed under pressure.

Hydrostatic Fluid Film Bearing

A bearing where external lubrication creates pressure to keep surfaces apart, independent of rotation; can support stationary shafts.

Rolling Element Bearing

Bearings that use rolling elements (balls or rollers) to transmit loads.

Advantages of Rolling Element Bearings

Allow higher-speed operation, generally do not require constant lubrication, and typically wear slowly when properly lubricated.

Disadvantages of Rolling Element Bearings

Higher initial cost, require more radial space, less suitable for overloading or shock loading, can be noisier after wear, and are more easily damaged by foreign matter.

Bearing Nomenclature

Parts and terms used to describe a bearing, including inner/outer races, ball race, cage, bore, width, and related features.

Radial Load vs Axial Load

Radial load acts perpendicular to the shaft; axial load acts along the shaft; bearings may experience radial, axial, or combined loads.

Deep Groove Ball Bearing

Single-row ball bearing capable of carrying radial and axial loads, high-speed operation, and requiring little lubrication.

Angular Contact Ball Bearing

Ball bearing with offset raceways; supports heavier axial loads in one direction; can be paired in duplex arrangements (back-to-back or face-to-face).

Duplex Angular Contact Ball Bearings

Two angular contact bearings mounted side by side and clamped; configurations include back-to-back (DB) and face-to-face (DF).

Double Row Self-Aligning Ball Bearing

Two rows of balls with a common spherical outer raceway, allowing self-alignment and carrying light axial and radial loads.

Thrust Ball Bearing

Bearings with flat raceways designed to carry axial loads with low torque.

Cylindrical Roller Bearings

Roller bearings with cylindrical rollers; higher radial load capacity than equivalent radial ball bearings; NU/N series cannot carry axial load.

Double Row Spherical Roller Bearings

Bearings with spherical raceways that allow misalignment and can accommodate both radial and axial loads.

Bearing Designation (Type, Series, Bore)

Bearings are designated by a code combining Type, Series, and Bore (e.g., 6310 indicates deep groove ball bearing, medium-load series, bore 50 mm).

Bore Code

Two-digit code defining bore diameter; for bore sizes below 20 mm, codes 00=10 mm, 01=12 mm, 02=15 mm, 03=17 mm; codes 04 and above are multiplied by 5 to get bore in mm (04=20 mm, 06=30 mm, etc.).

Basic Dynamic Load Rating (Cr)

Cr is the basic dynamic load rating, representing the bearing’s capacity under dynamic loading and used in life calculations.

Life Equation

An equation that relates bearing life (L10h) to dynamic load, rating, and life/speed factors; life is adjusted by factors f (life) and fr (speed) derived from nomograms.

Dynamic Equivalent Load (Pr)

Pr = X Fr + Y Fa; the effective load used in life calculations, where X and Y depend on bearing type and arrangement.

X and Y Factors

Coefficients used in Pr that depend on arrangement and contact angle (e.g., single, DT, DB, DF configurations).

Life Factor (f) and Speed Factor (fr)

Dimensionless factors obtained from nomograms; f relates to life (L10h) and fr relates to speed rating, used to compute Pr and life.