There are essentially two choices for the material used in ball bearings - chrome steel or stainless steel. Since the material plays a major part in the performance of a bearing in any given application, it is very important that the correct material is used. Note that the specified material applies to the load bearing components only - the rings and the balls. The retainer and the shields (if used) are usually made from a different material and are subject to separate specification.

CHROME STEEL (AISI 52100 OR EQUIVALENT)

This is the standard material used for ball bearing applications where load capacity is the main consideration. The machinability of this steel is excellent, giving smooth, low noise raceway finishes, together with superior life. Chrome steel material is recommended in applications where corrosion is not a factor.

CHEMICAL COMPOSITION (%): C CARBON Si SILICON Mn MANGANESE P PHOSPHOROUS S SULPHUR Cr CHROMIUM Mo MOLYBDENUM .95 - 1.1 .15 - .35 Max .5 Max .025 Max .025 1.3 - 1.6 - Hardness: 60 - 64 Rockwell C

STAINLESS STEEL

400 series martensitic stainless steel is the standard material for miniature and instrument ball bearings where corrosion resistance is more important than load capacity. There are 3 types of 400 series stainless steel used in the bearings described in this handbook. These materials have evolved in response to different manufacturing and application needs. It is important to note that the actual material used is generally determined by the manufacturer, and cannot be specified by the user. The bearing part numbering system gives the appropriate codes for each material type.

DR Stainless steel

This material is used in the manufacture of most corrosion-resistant bearings. It has been specifically developed to give excellent lifetime and low noise characteristics, combined with superior corrosion-resistance.

CHEMICAL COMPOSITION (%): C CARBON Si SILICON Mn MANGANESE P PHOSPHOROUS S SULPHUR Cr CHROMIUM Mo MOLYBDENUM .6 - .7 Max 1.0 Max 1.0 Max .03 Max .01 12 - 13.5 Max .25 Hardness: 58 - 60 Rockwell C

AISI 440C STAINLESS STEEL

The use of 440C material has declined in favor of other, more modern stainless steel formulations. However, it is still widely available and has very high resistance to corrosion.

CHEMICAL COMPOSITION (%): C CARBON Si SILICON Mn MANGANESE P PHOSPHOROUS S SULPHUR Cr CHROMIUM Mo MOLYBDENUM .95 - 1.2 Max 1.0 Max 1.0 Max .04 Max .03 16 - 18 Max .75 Hardness: 58 - 60 Rockwell C

ES1 STAINLESS STEEL

This is a relatively new stainless steel formulation with excellent machinability that allows raceway finish characteristics approaching those of chrome steel, combined with a corrosion-resistance at least the equal of AISI 440C.

CHEMICAL COMPOSITION (%): C CARBON Si SILICON Mn MANGANESE P PHOSPHOROUS S SULPHUR Cr CHROMIUM Mo MOLYBDENUM .44 - 46 .2 - .4 .2 - .4 Max .03 Max .01 12.8 - 13.2 Max .25 Hardness: 58 - 60 Rockwell C Tags: Bearing of China, Bearing Products, Bearing Technical