Bearing Materials
SAE 52100 Chrome Steel Balls
• Higher hardness for longer life ratings
• Low cost for high performance
• Good for temperatures up to 150°C
• Poor corrosion resistance (if left exposed)
This is the standard steel for most ball bearings. It is harder than stainless steel and gives greater life ratings. It also has superior low noise qualities to standard 440 grade stainless steel. Chrome steel actually has a low chromium content and is not corrosion resistant, all Plaig bearings are assembled with Shell AF2 Oil as chrome bearings require an oil coating on the exterior surfaces to protect against corrosion which can contaminate the inside of the dry bearing. Chrome steel can tolerate continuous temperatures of up to 150°C. Above this temperature, bearing life is significantly reduced.
440 Grade Stainless Steel Balls
• Excellent corrosion resistance to water, salt water and many chemicals
• Good for temperatures up to 500°C
• Suitable for cryogenic applications down to -250°C
440 grade stainless steel bearings are used for greater corrosion resistance to seawater, salt spray and some acids/alkalis. They are suitable for very high temperature applications as the steel is useful in temperatures of up to 500°C. They can also be used in cryogenic applications as the steel retains its toughness down to -250°C.
Silicon Nitride Ceramic Balls (Si3N4)
• Very good corrosion resistance to water, salt and chemicals
• Good high temperature performance up to 1,000°C
• Non magnetic and electrically insulated
• Lighter than steel balls
• Very low heat expansion, less expansion and contraction between heating and cooling.
Ceramic Bearings can run faster than all steel bearings due to the lower centrifugal force generated by the ceramic balls, the speed increase for Ceramic Bearings is 30 - 40% with adequate lubrication. Ceramic Bearings are less subjected to ball skidding under initial acceleration / torque. This allows the bearing to last longer and be far more reliable. Low heat expansion allows the bearing retainers to last longer. There are no downsides to Ceramic Bearings other than they cost more to manufacture.
PTFE Heat Resistant Rubber Seals
• Excellent corrosion resistance to water, salt water and most chemicals
• Good high temperature performance.
• Non magnetic
• Only semi-precision grade is possible
• Maximum temperature 260°C
The PTFE Seal is rubber bonded to a metal washer. The inner lip of the seal rubs against the bearing inner ring to provide an effective seal against smaller particles such as dust and moisture while preventing lubricant leakage.
Contactless Metal Shields
Metal Shields are designed to prevent larger particles from entering the bearing and also to keep grease inside the bearing. As the shields make no contact with the inner ring, they do not increase starting or running torque, but they do allow for much higher RPM's.
Bearing Retainer / Cage
Retainers keep the balls evenly spaced around the raceway preventing ball to ball contact and thus allowing higher speeds. They also help to retain grease around the balls and raceways.
The type of retainer used depends on the purpose of the bearing, if a specific retainer type is required please get in touch prior to purchasing and we can give details of what retainer is used in what bearings.