Frequently Asked Questions

1-) How should the bearing life calculation be done?

Once the bearing type is selected, the size is determined according to either the static load carrying capacity or the dynamic load carrying capacity. If the bearing is not operating for a long period of time or is turning too slowly, it is selected according to the static load carrying capacity, and if it is operating for a relatively long time, it is selected according to the dynamic load carrying capacity. Determination of the dimension according to the static load carrying capacity: The account of the static load carrying capacity is made on the basis of a certain permanent deformation of the bearing under constant load. In order to be able to compare the loads on the bearing to the load carrying capacity given in the catalog, we must reduce the effect of the radial and axial loads acting on it to a single equivalent charge.

Equivalent charge (Po) for static load carrying capacity:

Po=Xo.Fr + Yo.Fa

Fr: Rulmana gelen radyal yük,
Fa: Rulmana gelen eksenel yük,
Xo: Statik radyal faktör,
Yo: Statik eksenel faktör,

(Xo and Yo values have different values according to Fa / Fr ratio. For this reason, it is first necessary to find the ratio Fa / Fr and then select the coefficients Xo and Yo according to this ratio.) After determining Fr, Fa, Xo and Yo; the static equivalent charge, Po, can be found. When this value is compared to the static load number Co in the catalog, we find out how safe the bearing is: Co / Po gives us the safety coefficient at that load.
Dynamic load carrying capacity is based on life calculation (not permanent deformation).

Equivalent load (P) for dynamic load carrying capacity:P = XFr + YFa


Fr: Radial load on the bearing,
Fa: Axial load on the bearing,
X: radial factor,
Y: axial factor,

Similar to the calculation of the static load carrying capacity, the X and Y values take different values according to the Fa / Fr ratio. For this reason it is first necessary to find the ratio Fa / Fr and then to select the X and Y coefficients according to this ratio. After the determination of Fr, Fa, X and Y, the dynamic equivalent load P can be found. Since the dynamic loads are based on life expectancy, the C value in the catalog shows the load that can be carried over a lifetime of one million cycles (from 90 to 100 bearings).

How many millions of cycles will the bearing on the P equivalent load is found with the following formula:

For ball bearings, L = (C / P) ^ 3 – For roller bearings L = (C / P) ^ (3/10)

L: Milyon devir cinsinden ömür.
C: (Kataloglarda verilen) dinamik yük sayısı,
P: (Hesap edilen) eşdeğer dinamik yük,

The lifetime in hours of operation can be calculated using the number of cycles of mile per minute (n).

Lifetime in working hours =L*10^6/(60*n)

2 -) What are the factors affecting the bearing life?

Unfortunately, user errors lead the factors affecting the bearing life. Incorrect bearing selection, assembly failure, incomplete and incorrect lubrication are the main causes of user errors. It is important that you get help from your supplier about the selection and use of the bearing according to the application location.

3 -) How to determine the amount of bearing grease?

Lubrication fulfills the following tasks in a bearing:

  • Lubrication of sliding surfaces (reduction in friction between the balls or rollers and the cage)
  • Lubrication of rotating surfaces (balls or rollers and bearings)
  • Protection against corrosion-rust in the bearings
  • prevention of external influences (dust, humidity, etc.) from entering the bearing,
  • Helping to transfer heat (heat to the outside of the bearing)

If the bearings come to you in an oil-free way, you must absolutely grease them.

General Advices:

  • n x dm > 100.000 [min-1 mm],

To fulfill the 20% and 25% of the gap,

  • n x dm < 50.000 [min-1 mm],

In a way that filling 100% of the space,

  • The space between the bearing and

the right and left of the bearing must be lubricated so that 50%

of the gap is filled.

 4 -) What are the differences between grease and and lubrication with oil?

5 -) What are the differences between the bearing with cap and the capless roller bearing?

The most important difference between capped bearings and capless bearings is that the capped version protects the bearing from unwanted foreign particles. Another advantage is the storage of the grease in the roller bearing with the cover version. However, it is a disadvantage that some versions of the sealed bearings in contacted bearings operate at lower speeds than the non-frictionally welded version in some versions.

Covered bearings are basically divided into two according to the application;

  • Contact impermeatibility (plastic covered bearings): full protection from foreign particles, low speeds
  • Non-contact sealing (steel ball capped bearing): partial protection from foreign particles, higher speeds than plastic version.

6 -) What does Internal Clearance mean?

In order to allow the roller to be expanded together with the temperature increase that occurs at high speeds in the working conditions according to the application, the roller bearings are available in different grades according to a specific standard by the manufacturer. It is possible to expect to operate at higher speeds than in the case of options with too much bearing space, in principle less friction. However, in applications where we expect the system to run more rigid, a lower gap class may be preferred. Depending on the application, it is important that you receive relevant support from your supplier.

7-) What are the main differences between ceramic ball bearings and steel ball bearings?

The most fundamental difference between ceramic ball bearings and steel ball bearings is that ceramic ball bearings can operate at lower speeds with less temperature depending on the friction coefficient comparison. However, when evaluated in terms of cost, ceramic ball bearings are more expensive than steel ball bearings.

8 -) Is there any difference in the load carrying capacity between the stainless steel bearing and the non-stainless bearing?

In principle, they have the same load carrying values, depending on the type of product and application.

9 -) What are the main differences between a full complement ball bearing and a bearing with a retainer?

The most important feature of the cage in the rolling element is to prevent contact between the rolling elements and to provide moving it in a certain way. However, in some applications it is possible to increase the load carrying capacity without changing the main dimensions of the roller (inner diameter, outer diameter, thickness), but it is possible to remove the cage structure and increase the load carrying capacity with a larger number of rolling elements. It is called a full complement bearing, in which the cage structure of the roller is removed and replaced with a larger number of rolling elements. The main difference between these two types is that the cageless bearing has higher load carrying capacity than the cage type with the same dimensions and can operate at lower speeds. Depending on the application, it is important that you receive relevant support from your supplier.

10 -) What are the advantages and disadvantages of Thin Section bearings?

Thin-section bearings, which are mostly found in defense industry and aerospace applications, are used to save space in finer dimensions with geometries and special designs and at the same time to meet the same requirements at higher sensitivity rates. However, they can accrue at higher costs than standard bearing types. See thin section bearings

11 -) Can rail-cars and nut-screws work with each other in different brands of linear motion systems?

Different brands of ray-cars; nuts-screws can not work with each other. A car or nut of the same brand must be used on a rail or a screw.

12 -) What does bearing preloading mean in linear motion systems?

In linear bearings as well as in rotary bearings, pre-loading can be achieved with less bearing clearance. The size of the preload varies with the application, but in principle it is too high, allowing the bearing to move in a more rigid state, causing it to operate at lower speeds. It is important that you receive support from your supplier to select the correct preload value according to the application.