Applied Product Catalog 2016 2017 Page i21 Technical Reference

Bearings All Things Industrial SM i21 Continued on next page. Improper lubrication and contamination are responsible for 70% of all early bearing failures. Dirt is responsible for more than 90% of all bearing troubles. Bearing life is reduced by approximately 20% with outer race rotation. When a bearing is press fitted onto a steel shaft or press fitted into steel or cast iron housings, the internal clearance is reduced by 80% of fit interference. Deep groove ball bearings (Conrad) are ideally designed to permit radial loading and thrust loading from either direction (the combined load should not exceed 100% of radial load rating). Maximum type ball bearings (with precision ground filling slots) have a radial capacity of 10-15% more than the Conrad type. Thrust is limited to approximately 10% of radial capacity. The angular contact design permits this bearing to carry high thrust in ONE DIRECTION ... Equal to 150% of its radial load capacity. Double row ball bearings combine the features of two single row angular contact bearings mounted in duplex. Always check bearing fit-up after assembly. Recommended shaft finishes for Grade 1 bearings under 2" - max. 32 rms; over 2" - max. 64 rms; housing bores - 125 rms max. High points of eccentricity of inner and outer races of high precision bearings are marked with a burnished spot on one face. It is desirable to press needle bearings from the lettered end. Do not check O.D. of a drawn cup needle bearing unmounted. Bearings lubricated with petroleum greases have a shelf life of approximately seven years. If you double the speed of a bearing, you cut its life in half. If you double the load on a ball bearing, you cut its life to 1/8 of its original life. Coefficient of thermal expansion for steel is .00007 inch per F. Bearing Facts Common Causes of Bearing Failures FOREIGN MATERIAL Typical causes include improper cleaning methods, poor oil filtration, or seal wear. Hard particle contamination Contamination bruising Fine particle contamination Internal cage wear from fine particle contamination CORROSION/ETCHING Typical causes include damaged packaging, improper storage, and worn or damaged seals. Roller-spaced spalling Corrosion on the outer ring race Etching and corrosion Advanced corrosion and spalling FATIGUE SPALLING Typical causes include high load, misalignment, and stress concentration. Fatigue spalling on a cylindrical roller bearing Point Surface Origin (PSO) spalling Fatigue spalling on ball bearing inner ring Geometric Stress Concentration (GSC) spalling EXCESSIVE PRELOAD, OVERLOAD AND ROLLOUT Typical causes include excessive load, and/or misalignment, and improper mounting procedure. Roller fracture Peeling Rollout in bearing outer ring Outer ring subcase fracture MISALIGNMENT Typical causes include high load, shaft or housing deflection, inaccurate housing, or shaft machining. Irregular roller path caused by deflection Geometric Stress Concentration (GSC) spalling Irregular roller path (180 degree opposite of above) Geometric Stress Concentration (GSC) spalling on bearing outer ring INADEQUATE LUBRICATION Typical causes include improper grease or oil viscosity, low flow rate, and high operation temperatures. Race deformation from excessive heat generation Peeling/Scoring damage on roller end Complete bearing lockup Rib and roller end scoring Photos courtesy of The Timken Company.

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