For long term performance ball bearings must have some form of lubrication. Grease and oil is recommended whenever the application will allow it.

Generally grease is selected for low to medium speed applications and oil is selected for high speed applications.

Special environments such as vacuum, high and low temperatures may not allow conventional lubrication. In some applications the addition of grease or oil could contaminate a product. Many specialty lubrications are available to satisfy specific operating conditions.

For low speed low load applications or for when cleanliness and vacuum call for it a solid dry film lubricant coating such as Tungsten Disulfide or Moly Disulfide is a viable option.

Many specialty lubrications are available to satisfy specific operating conditions those listed below are our most common and are for comparison purposes only. There is no perfect lubrication and for specialty applications selection is made on a case by case basis. Data sheets should be analyzed for suitability.

SOLID LUBRICANTS

Solid lubricants offer excellent lubrication under extreme conditions.

When conditions exceed the limitations of wet lubricants as is found in high temperature vacuum applications, a dry solid lubricant coating can provide the boundary between rolling element and raceway reducing stress and increasing life.

These coatings are most beneficial to all steel bearings running dry where the boundary created by the coating can reduce micro-welding. For hybrid type bearings coatings can add additional life for critical applications.

Internal clearance is the play within a ball bearing. It is the geometrical clearance between the inner ring, outer ring and ball. It is a critical factor in bearing selection that will directly impact bearing life. It is often overlooked, particularly as to how it is reduced by interference fits.

Radial clearance is the play between the ball and raceway perpendicular to the bearing axis. Axial clearance is the play parallel to the bearing axis and is typically at least 10 times greater than the radial clearance. Generally, internal radial clearance will be reduced 80% of the interference fit amount.

Too little or too much internal clearance will significantly influence factors such as heat, vibration, noise, and fatigue life.

In extreme applications that see high or low temperatures this clearance needs to be considered in the overall design to compensate for thermal expansion and contraction of housings and shafts.

SELECTING BEARING CLEARANCE (GENERAL GUIDELINES)

DEEP GROOVE BALL BEARING RADIAL INTERNAL CLEARANCE (UNITS: ΜM)

The retainer keeps the balls equally spaced providing equal load distribution and prevents unnecessary wear of the rolling elements.

A retainer material with fillers can provide certain lubrication benefits as normal wear occurs. Numerous composite materials are available that are not listed here that can meet certain environmental and functional requirements.

Please contact us for further information.

PEEK and Vespel are generally considered vacuum compatible.

PPS offers the greatest chemical resistance and along with PEEK is FDA and USDA compliant.

PEEK and PPS offer the highest speed capability as a retainer material

Material compatibility in critical and or sensitive environments such as vacuum applications is subject to your bench testing and data sheet evaluation.

Since application environments vary greatly the following chart is simply a guideline.

RETAINER MATERIALS

*d=inner bore diameter,N=RPM
%; Inner ring piloted, open configuration

RING AND BALL MATERIALS

CHROME STEEL

Chrome steel is one of a class of non stainless steels such as AISI 52100, En31, SUJ2, 100Cr6, 100C6, DIN 5401 which are used mostly in bearings

CERAMIC

• Hybrid and full ceramic bearings are made using silicon nitride or zirconium oxide material.
• Hybrid bearings are constructed of steel inner/outer rings, ceramic balls and retainers made of steel or thermoplastic.
• Full ceramic bearings are 100% ceramic. Balls, rings and retainers.
• The density of ceramic is 40% that of steel, the resulting reduction in weight reduces centrifugal forces imparted on the rings, reducing skidding, allowing up to 30% higher running speeds with less lubrication.
• Silicon nitride balls have a 50 % higher modulus of elasticity (resistance to deformation) than steel, which increases rigidity and improving accuracy.
• Ceramic balls have a smoother finish than steel, vibration and spindle deflection is reduced allowing higher speeds.
• Ceramic has a lower coefficient of friction and is nearly twice as hard as bearing steel resulting in less wear with less lubrication. Bearing life can be increased.

Heat treated high carbon chromium bearing steel is the most common material used for rings and balls. Due to it low chromium content it exhibits poor corrosion resistance. The material does exhibit good mechanical properties up to 250F continuously. Above 250F bearing life is reduced as well as load capacity. Dimensional changes occur that require compensation in the overall bearing design and bearing fits. Applications are wide for this material. 52100 is magnetic.

440C STAINLESS STEEL

Heat treated 440C stainless steel offers fair to good corrosion resistance. It is the most common stainless steel used for rings and balls. With the addition of chromium and nickel corrosion resistance is greatly improved over 52100 steel. As oxygen reacts with the chromium a protective layer of chromium oxide is formed on the surface. This material can be passivated to improve corrosion resistance. Load capacity of 440C is about 20% less than that of 52100. With design considerations this material can handle service temperature up to 350F with fair load capacity. Beyond 350F capacity and life is reduced.

Applications may include some vacuum and clean processes or where general preventative corrosion resistance is desired. This material is magnetic.

300 SERIES STAINLESS STEEL (316 & 304)

In a semi-precision grade bearing, 300 series stainless steel can be chosen for improved corrosion resistance over 440C. These materials are not heat treated so load capacity is significantly less than HT 52100 & 440C. It can be used for both rings and balls or SS rings with ceramic balls. 300 series stainless steel offers excellent corrosion resistance to water and excellent to good resistance when exposed to certain common acids. This material can be an excellent choice for food grade applications. Other applications may include marine and vacuum processes. 300 series stainless steel is also a common material used for ribbon and crown type retainers. 300 series stainless steels are generally considered non-magnetic. As 300 series bearings are not as common as 440C, size availability and minimum order requirements apply.

PLASTICS

Numerous types of plastics can be used to produce semi-precision bearings.
Environment compatibility determines the variety. Acetal (Delrin) is the most common for the rings with balls of either acetal or stainless steel. Other Materials such as PEEK, PPS, Vespel, Nylon and many others can be used for the rings.

Lightly loaded low RPM applications requiring corrosion resistance, non-magnetic/non-metallic and or lightweight bearings may benefit from a plastic ball bearing. Sizes start at 8mm inner diameter. Minimum order requirements may apply.

CERAMIC MATERIAL PROPERTIES

THERMAL

ELECTRICAL

CERAMIC VS. STEEL VS. STAINLESS STEEL

CORROSION RESISTANCE COMPARISON CHART

WATER

FOOD

DILUTE ACIDS

ACIDS

A = excellent, B = good, C = fair, D = poor, NC = Not compatible

CHEMICAL COMPOSITION OF BEARING STEELS

Chrome Steel

Stainless Steel

To help retain bearing lubrication and prevent contamination from the environment a seal (contact) or shield (non-contact) can be employed.

Often no seal (Open) is required when the bearing will be housed and externally lubricated or when operated in a vacuum.

TYPES

‘Z’ Type Shield – The ‘Z’ type shield is a metal shield that typically is non-removable after installation as is it pressed in. There is a small gap about .005 inches between the shield and inner race. There is no contact so obtainable speeds and torque are not effected as in a contact type seal. Lubricant leakage can occur and contamination can enter through this gap. They have fair dust resistance and poor water resistance. Shields are good to around 350 F.

‘RS’ Type Seal – The ‘RS’ type seal is a rubber seal that makes contact with the inner race. Most commonly made of Buna-rubber. They are removable. They offer the best sealing against contamination and lubricant leakage. Generally the speed rating is reduced about 35% that of the ‘Z’ type or open and torque is increased.  Temperature range is 15 F to 220 F.

‘V’ Type Seal – The ‘V” type seal is a non-contact type rubber seal that does not contact the inner  race, but rides in groove machined in the inner races creating a labyrinth effect. Its performance falls between a metal shield and contact type rubber seal.  Most commonly made of Buna-rubber. They are removable. They offer the good sealing against contamination and lubricant leakage. Generally the speed rating is not reduced and is comparable to that of the ‘Z’ type or open. There is no seal induced torque increase. Temperature range is 15 F to 220 F.

‘T’ Type Seal – The ‘T’ type seal is made of glass reinforced Teflon. This type of seal is removable and easily replaced. In most configurations the seal is held in place by a snap ring. The level of contact (sealing) can be adjusted to meet application requirements all the way from non-contact to heavy contact. Their best characteristic would be their high temperature capability of 500 F.

The ideal mounting for a precision bearing is line to line on both shaft and housing. Such a fit has no interference or looseness. For random fitting the fit tolerances may need to be increased to meet the lot variances. For selective fitting the bearing inner and outer diameter should be accurately measured, then the shaft and housing machined to suit.

Interference fits should be used with care as they can distort the raceway and reduce radial internal clearance. In preloaded pairs, reducing the internal radial clearance increases the preload. If excessive, the results can be significantly reduced speed capability and higher operating temperatures which will ultimately reduce life.

Some applications require interference fits such as:

• Heavy radial loading
• Intense vibration
• Lack of axial clamping

Radial internal clearance is reduced by approximately 80% of the interference fit.

Interference fits are usually applied to the rotating ring.

Loose fits may be suggested when:

• Axial clamping is possible, such a snap rings, locking collars or adhesive
• Ease of assembly
• Axial movement is required for spring preload or thermal movements

Fits are often overlooked and is arguably the most common bearing handling mistake.
The table below is simply a guideline as there are many influencing factors to be considered such as.

• Load, speeds and temperatures
• Ease of assembly and disassembly
• Rigidity and accuracy requirements
• Machining tolerances

Therefore the appropriate fit may fall somewhere in between.

L = Loose fit, T = Tight fit, d = Bearing I.D., D = Bearing O.D.

INNER RING TOLERANCE

ABEC 1 / ABEC 3
VALUES ARE IN .0001″

INNER RING TOLERANCE

ABEC 5 / ABEC 7
VALUES ARE IN .0001″

OUTER RING TOLERANCE

ABEC 1 / ABEC 3
VALUES ARE IN .0001″

OUTER RING TOLERANCE

ABEC 5 / ABEC 7
VALUES ARE IN .0001″

Internal clearance is the play within a ball bearing. It is the geometrical clearance between the inner ring, outer ring and ball. It is a critical factor in bearing selection that will directly impact bearing life. It is often overlooked, particularly as to how it is reduced by interference fits.

Radial clearance is the play between the ball and raceway perpendicular to the bearing axis. Axial clearance is the play parallel to the bearing axis and is typically at least 10 times greater than the radial clearance. Generally, internal radial clearance will be reduced 80% of the interference fit amount.

Too little or too much internal clearance will significantly influence factors such as heat, vibration, noise, and fatigue life.

In extreme applications that see high or low temperatures this clearance needs to be considered in the overall design to compensate for thermal expansion and contraction of housings and shafts.

SELECTING BEARING CLEARANCE (GENERAL GUIDELINES)

DEEP GROOVE BALL BEARING RADIAL INTERNAL CLEARANCE (UNITS: ΜM)

The retainer keeps the balls equally spaced providing equal load distribution and prevents unnecessary wear of the rolling elements.

A retainer material with fillers can provide certain lubrication benefits as normal wear occurs. Numerous composite materials are available that are not listed here that can meet certain environmental and functional requirements.

Please contact us for further information.

PEEK and Vespel are generally considered vacuum compatible.

PPS offers the greatest chemical resistance and along with PEEK is FDA and USDA compliant.

PEEK and PPS offer the highest speed capability as a retainer material

Material compatibility in critical and or sensitive environments such as vacuum applications is subject to your bench testing and data sheet evaluation.

Since application environments vary greatly the following chart is simply a guideline.

RETAINER MATERIALS

*d=inner bore diameter,N=RPM
%; Inner ring piloted, open configuration

RING AND BALL MATERIALS

CHROME STEEL

Chrome steel is one of a class of non stainless steels such as AISI 52100, En31, SUJ2, 100Cr6, 100C6, DIN 5401 which are used mostly in bearings

CERAMIC

• Hybrid and full ceramic bearings are made using silicon nitride or zirconium oxide material.
• Hybrid bearings are constructed of steel inner/outer rings, ceramic balls and retainers made of steel or thermoplastic.
• Full ceramic bearings are 100% ceramic. Balls, rings and retainers.
• The density of ceramic is 40% that of steel, the resulting reduction in weight reduces centrifugal forces imparted on the rings, reducing skidding, allowing up to 30% higher running speeds with less lubrication.
• Silicon nitride balls have a 50 % higher modulus of elasticity (resistance to deformation) than steel, which increases rigidity and improving accuracy.
• Ceramic balls have a smoother finish than steel, vibration and spindle deflection is reduced allowing higher speeds.
• Ceramic has a lower coefficient of friction and is nearly twice as hard as bearing steel resulting in less wear with less lubrication. Bearing life can be increased.

Heat treated high carbon chromium bearing steel is the most common material used for rings and balls. Due to it low chromium content it exhibits poor corrosion resistance. The material does exhibit good mechanical properties up to 250F continuously. Above 250F bearing life is reduced as well as load capacity. Dimensional changes occur that require compensation in the overall bearing design and bearing fits. Applications are wide for this material. 52100 is magnetic.

440C STAINLESS STEEL

Heat treated 440C stainless steel offers fair to good corrosion resistance. It is the most common stainless steel used for rings and balls. With the addition of chromium and nickel corrosion resistance is greatly improved over 52100 steel. As oxygen reacts with the chromium a protective layer of chromium oxide is formed on the surface. This material can be passivated to improve corrosion resistance. Load capacity of 440C is about 20% less than that of 52100. With design considerations this material can handle service temperature up to 350F with fair load capacity. Beyond 350F capacity and life is reduced.

Applications may include some vacuum and clean processes or where general preventative corrosion resistance is desired. This material is magnetic.

300 SERIES STAINLESS STEEL (316 & 304)

In a semi-precision grade bearing, 300 series stainless steel can be chosen for improved corrosion resistance over 440C. These materials are not heat treated so load capacity is significantly less than HT 52100 & 440C. It can be used for both rings and balls or SS rings with ceramic balls. 300 series stainless steel offers excellent corrosion resistance to water and excellent to good resistance when exposed to certain common acids. This material can be an excellent choice for food grade applications. Other applications may include marine and vacuum processes. 300 series stainless steel is also a common material used for ribbon and crown type retainers. 300 series stainless steels are generally considered non-magnetic. As 300 series bearings are not as common as 440C, size availability and minimum order requirements apply.

PLASTICS

Numerous types of plastics can be used to produce semi-precision bearings.
Environment compatibility determines the variety. Acetal (Delrin) is the most common for the rings with balls of either acetal or stainless steel. Other Materials such as PEEK, PPS, Vespel, Nylon and many others can be used for the rings.

Lightly loaded low RPM applications requiring corrosion resistance, non-magnetic/non-metallic and or lightweight bearings may benefit from a plastic ball bearing. Sizes start at 8mm inner diameter. Minimum order requirements may apply.

CERAMIC MATERIAL PROPERTIES

THERMAL

ELECTRICAL

CERAMIC VS. STEEL VS. STAINLESS STEEL

CORROSION RESISTANCE COMPARISON CHART

WATER

FOOD

DILUTE ACIDS

ACIDS

A = excellent, B = good, C = fair, D = poor, NC = Not compatible

CHEMICAL COMPOSITION OF BEARING STEELS

Chrome Steel

Stainless Steel

To help retain bearing lubrication and prevent contamination from the environment a seal (contact) or shield (non-contact) can be employed.

Often no seal (Open) is required when the bearing will be housed and externally lubricated or when operated in a vacuum.

TYPES

‘Z’ Type Shield – The ‘Z’ type shield is a metal shield that typically is non-removable after installation as is it pressed in. There is a small gap about .005 inches between the shield and inner race. There is no contact so obtainable speeds and torque are not effected as in a contact type seal. Lubricant leakage can occur and contamination can enter through this gap. They have fair dust resistance and poor water resistance. Shields are good to around 350 F.

‘RS’ Type Seal – The ‘RS’ type seal is a rubber seal that makes contact with the inner race. Most commonly made of Buna-rubber. They are removable. They offer the best sealing against contamination and lubricant leakage. Generally the speed rating is reduced about 35% that of the ‘Z’ type or open and torque is increased.  Temperature range is 15 F to 220 F.

‘V’ Type Seal – The ‘V” type seal is a non-contact type rubber seal that does not contact the inner  race, but rides in groove machined in the inner races creating a labyrinth effect. Its performance falls between a metal shield and contact type rubber seal.  Most commonly made of Buna-rubber. They are removable. They offer the good sealing against contamination and lubricant leakage. Generally the speed rating is not reduced and is comparable to that of the ‘Z’ type or open. There is no seal induced torque increase. Temperature range is 15 F to 220 F.

‘T’ Type Seal – The ‘T’ type seal is made of glass reinforced Teflon. This type of seal is removable and easily replaced. In most configurations the seal is held in place by a snap ring. The level of contact (sealing) can be adjusted to meet application requirements all the way from non-contact to heavy contact. Their best characteristic would be their high temperature capability of 500 F.

The ideal mounting for a precision bearing is line to line on both shaft and housing. Such a fit has no interference or looseness. For random fitting the fit tolerances may need to be increased to meet the lot variances. For selective fitting the bearing inner and outer diameter should be accurately measured, then the shaft and housing machined to suit.

Interference fits should be used with care as they can distort the raceway and reduce radial internal clearance. In preloaded pairs, reducing the internal radial clearance increases the preload. If excessive, the results can be significantly reduced speed capability and higher operating temperatures which will ultimately reduce life.

Some applications require interference fits such as:

• Heavy radial loading
• Intense vibration
• Lack of axial clamping

Radial internal clearance is reduced by approximately 80% of the interference fit.

Interference fits are usually applied to the rotating ring.

Loose fits may be suggested when:

• Axial clamping is possible, such a snap rings, locking collars or adhesive
• Ease of assembly
• Axial movement is required for spring preload or thermal movements

Fits are often overlooked and is arguably the most common bearing handling mistake.
The table below is simply a guideline as there are many influencing factors to be considered such as.

• Load, speeds and temperatures
• Ease of assembly and disassembly
• Rigidity and accuracy requirements
• Machining tolerances

Therefore the appropriate fit may fall somewhere in between.

L = Loose fit, T = Tight fit, d = Bearing I.D., D = Bearing O.D.

INNER RING TOLERANCE

ABEC 1 / ABEC 3
VALUES ARE IN .0001″

INNER RING TOLERANCE

ABEC 5 / ABEC 7
VALUES ARE IN .0001″

OUTER RING TOLERANCE

ABEC 1 / ABEC 3
VALUES ARE IN .0001″

OUTER RING TOLERANCE

ABEC 5 / ABEC 7
VALUES ARE IN .0001″