STEP 1: Select a Follower-Roller bearing Manufacturer

STEP 2: Select a Roller Bearing from the table

Note: Click a Header to sort by that Header. For example, click OD to sort by Outside-Diameter. 1.Click a Part-Number from the table

Cam-Follower Radius & Follower-Roller Part- Number

IMPORTANT NOTES A.Before you select a Roller in the list of bearings, you must use the Part-Editor to add a Circle and add a Radius for the Circle. B.When you select a Roller in the list of bearings, the Radius dimension of the Circle changes IMMEDIATELY to the OD/2 of the bearing you select (± Radial Clearance). C.The Part-Number of the Roller is in the graphics-area under the Radius dimension - see image above D.The Radius dimension of the Circle sketch-element that represents the Roller is now read-only. To change the Radius of the Roller: •Select a different Part-Number for the Roller bearing or •Disable Show Roller and Cam Lifetimes check-box, and then edit the Radius dimension with the Part-Editor.

You can see immediately the Basic Rating Life, in the L10 for Roller: Part Number  separator.

To see these factors, select “Enable the ISO 281 Modification Factors”

We calculate for you the and modification factors as you enter the parameters below.

ISO 281 Modification Factors

Reliability Factor (a1)

•Reliability drop-down: Use the drop-down to select, from a list of reliability percentages.

The drop-down list shows the Reliability Factors (90 to 99.95%) as given in ISO 281.

or

•Reliability Factor: as a percentage.

In this case, we find for you the factor nearest to a Reliability Factor in the drop-down list.

Operating Viscosity

The oil's viscosity at the operating temperature (or Base Oil in a Grease) is function of its Viscosity Grade and Viscosity Index.

We calculate the oil's viscosity for you when you enter these five parameters:

•Operating Temperature,

•Temperature , and Viscosity at Temperature

•Temperature , and Viscosity at Temperature

Rules:

• and

Note:

If you know the ISO VG of the oil, you can enter these: and

Lubricating Oil and Grease datasheets usually provide the Viscosity at and at .

Lubrication Type

Select one of these lubrication methods:

◉Oil Filtered On-Line: Circulating oil lubrication with the oil filtered on-line before being supplied to the bearings

◉Oil Filtered Off-line: Oil bath lubrication, or circulating oil lubrication with off-line filters (or without filtration)

◉Grease.

ISO 281 does not consider Oil-Mist Lubrication.

Contamination Factors for each Lubrication-Type

Oil Filtered On-Line

Select, in the drop-down list box, the Filtration Ratio, .

The operating, or actual, Filtration-Ratio should be as high, and if not higher, than the Filtration-Ratio you select.

• - the contamination particle size, in μm, with ISO 11171 calibration.

• - filtration ratio at contamination particle size

The designation (c) signifies that the particle counters — of particles of size — shall be APC (automatic optical single-particle counter) calibrated in accordance with ISO 11171.

Also, the oil system shall have cleanliness within the range indicated by the cleanliness code according to ISO 4406 - for example, 17/14

Oil Filtered Off-Line

Select, in the drop-down list box, the Cleanliness Codes, according to ISO 4406, that best represents the anticipated operating condition.

Grease

Select, in the drop-down list box, the Level of Contamination that best represents the operating conditions.

We calculate these parameters for you when you select a Roller, and/or enable ISO 281 factors.

Life for the seleced Roller(Cam-Follower Bearing)

Basic Rating Life,

This states that if the bearing load, , is equal to the Basic Dynamic Load Rating, , then there is a 90% reliability that the bearing survives 1 million rotations, if manufactured with commonly used high quality material, of good manufacturing quality, and operating under conventional operating conditions.

Modified Rating Life,

Operating Life

The actual operating life is the life achieved by the bearing. It may differ significantly from the life we calculate.

It is not possible to calculate the actual operating life, as there is a range of possible installation and operating conditions. One method to estimate the operating life is to compare the installation and operating conditions with similar applications.

Possible factors that influence the Operating Life

The Reliability Factor is constant for all application conditions.

The drop-down list has the standard Reliability Factor percentages (90 to 99.95%), as given in ISO 281.

Modified Life Rating (at reliability) (millions of revolutions)

The Life Modification factor, , is a complex interaction between Oil or Grease Viscosity Grade, Filtration, Contamination, Oil Operating Temperature, the Fatigue load capacity of the Roller, the rotational-speed of the Roller, and the diameter of the Roller.

The equations given in ISO 281 to calculate these factors are empirical, complex, and interrelated. All of the factors, except , are a function of the bearing speed and bearing load. In a cam mechanism, the speed and load on the roller continually change. Therefore, we calculate for you the factors at each step and integrate them to find their equivalent values.

ISO 281 defines the fatigue load, , for a bearing as the load below which metal fatigue does not occur.

With poor lubrication, or contamination of the lubricant, the bearing can fatigue at loads which are significantly below the fatigue limit,.

For the fatigue limit to be a valid value, the lubricant film must fully separate the rolling elements from the raceways and that dents from contaminants from handling do not exist on the rolling surfaces.

The contamination factor, takes into account how the level of solid particle contamination of the lubricant influences the calculated bearing fatigue life. The particles cause indentations in the rolling surfaces of the bearing, and these indentations increase the local contact stress, which reduces the expected fatigue life.

• means perfectly clean conditions without any indentations.

• means severely contaminated conditions resulting in pronounced indentations.

In the SKF rating life model, contamination, designated by the contamination factor, , acts as a stress raiser, thereby reducing the fatigue load limit to .

We then compare the reduced fatigue load limit, , to the actual bearing load, , to give a fatigue resistance value of

•Conditions that are clean and a load that is less than the fatigue load limit give a high fatigue resistance value.

•Conditions that are contaminated and a load that is more than the fatigue load limit give a low fatigue resistance value.

The stress-raising influence of contamination on fatigue depends on a number of parameters, including: bearing size, relative lubricant condition, size and distribution of solid contaminant particles, and types of contaminants (soft, hard, etc.). Therefore, it is not meaningful to enter a value for the contamination factor that has general validity.

If a catalog does not list the Fatigue Load Limit, and the mean bearing diameter is less than . (nearly all Follower-Roller Bearings are less than ), then we use this approximation:

Roller and needle bearings, with a Mean Diameter < 100mm.

Ball bearings, with a Mean Diameter < 100mm

Mean Diameter = (Outside Diameter + Inside Diameter) / 2

The Viscosity Ratio, , indicates the quality of the lubricant film formation.

The lubricant-film separates the raceway and rolling-elements. It is expressed as:

Note 1: Viscosity Ratio, , assumes that surface finish is for good quality Follower-Roller bearings.

Note 2: An approximate relationship between Film Thickness Ratio and Viscosity Ratio, , is:

Notes:

A Viscosity-Ratio < 0.1 is outside of the limits of ISO 281. It is near to metal-to-metal contact.

A Viscosity-Ratio > 4 is the maximum that can be used by ISO 281.

ISO 281 states that a Viscosity-Ratio = 4 if it is actually you calculate it to be greater than 4.

A Viscosity-Ratio > 4 is getting too high for bearings. The needles or balls may slide and refuse to roll in the 'thick-oil', or the shearing of the oil may churn and increase the oil and bearing temperatures.

A Viscosity-Ratio in the range of is approximately ideal.

The Reference Kinematic-Viscosity, (sometimes called the Rated, or Required Viscosity) is the viscosity that is required to separate the surfaces, of the rolling elements and races in the Follower-Roller bearing..

It assumes that the oil is a mineral oil, with a Viscosity-Index of approximately 100.

Synthetic oils can be used.

if

if

- inside diameter of Follower-Roller

- outside diameter of Follower-Roller

We calculate for you the Viscosity, , at the Operating Temperature, , from the Viscosity at two other temperatures.

Nearly always, the two other temperatures are and , but not necessarily.

The lubricant's data-sheet usually specifies the Viscosity at ( ) and ( )

You must enter all four parameters in the dialog:

•2 x temperature: and  

•2 x viscosity: and at temperature and

•Operating-Temperature: .

We calculate the Viscosity at the Operating-Temperature, .

If a contaminant particle moves to the inside of a bearing the rollers (or balls), outer-race, and inner-race are prone to dent because of the small internal bearing clearances and the small rolling radii of the rollers (or balls). An indent leads to localized stress, which will decrease the life of the bearing.

The contamination may even prevent the rollers (or balls) rotating.

The contamination factors that reduce the lifetime of a Follower-Roller bearing are a function of the:

•diameter of the Follower-Roller

•lubricant film thickness (viscosity ratio, )

•size, type, and hardness of the particle contaminant.

Guide values for the contamination factor are in the table below. They are typical levels of contamination for well lubricated bearings.

Contamination and Lubrication Method.

We can find for you the contamination factors with these lubrication methods:

Circulating oil lubrication with On-Line Filtration, before being supplied to the bearings.

Oil bath Lubrication, or Recirculating Oil Lubrication, with Off-Line Filtration.

NOTE

Research concludes that it is difficult to accurately find the oil cleanliness especially if you analyze very clean oils. It is easy to pollute an oil-sample, with oil additives that precipitate into the oil and particle calculation.

Grease Lubrication, Contamination Factors

Simplified Values of Oil Contamination Factor ,

Contamination Level for Grease Lubrication

The table below provides scale values as a function of particle concentration (particles/ml) - it is from ISO 4406

A three number code defines the amount of contamination for three particle sizes: 4, 6, and 14 μm. Each time a number increases by 1, the quantity of particles is doubled for a particular particle size.

Example: ISO code = 21 / 19 / 17

This Contamination Class describes a fluid containing:

•between 10,000 and 20 ,000 particles of ≥ 4 μm(c) per 1 ml sample

•between 2,500 and 5 ,000 particles of ≥ 6 μm(c) per 1 ml sample

•between 640 and 1 300 particles of ≥ 14 μm(c) per 1 ml sample

If the leading number is missing, then that size of particle is not counted.