# High-precision cylindrical roller bearings

## Description

High-precision cylindrical roller bearings produced in single row and double row designs by SLF are ideal floating bearings. They are used not only as floating bearings, but also in applications demanding radially rigid, highly precise solutions with high load carrying capacity.
For exact radial clearance adjustment, in the standard version, the bearings are machined with a tapered hole (taper 1:12). Axial sliding on the shaft’s tapered seat face means that the desired radial clearance or radial preload can be adjusted.
These cylindrical roller bearings are also produced with a cylindrical hole. In this case, in the order designation, the “K“ (e.g. N1013M1.HP) is not used.

## Dimensions/standards

In high-precision cylindrical roller bearings, the main dimensions are standardized according to ISO 15 (Radial bearings – boundary dimensions) or DIN 616 (Roller bearings – boundary dimensions).

## Tolerances

Their intended use required that SLF high-precision cylindrical roller bearings have high accuracy and so they are normally produced in the HP tolerance class. This accuracy level corresponds to the SP tolerance class according to DIN 5412-4.
For applications with even more stringent requirements, we can produce bearings in the UP tolerance class according to DIN 5412-4.
The bearings can also be delivered with other tolerances upon request.

## Bearing design types

SLF produces double row high-precision cylindrical roller bearings in the NN30 and NNU49 series. The designation NN indicates that the bearing has two rows, and the inner ring is equipped with three shoulders, whereas the outer ring has none. In the NNU design type, the outer ring has three shoulders, but the inner ring has none.
We can deliver the outer ring with an oil groove and at least three oil holes upon request. For this design, enter ”S“ (for example, NN3012K.S.M.HP) in the order designation after the letter.
In this design, it is possible to feed the lubricant directly between the rollers.

## Clearance

High-precision cylindrical roller bearings have a standard radial clearance C1 that is smaller than the standard clearance CN. For this reason, the bearings are not interchangeable, meaning that the outer rings between the bearings cannot be exchanged, as is possible for the single row cylindrical roller bearings. Neither C1 nor NA (standing for German: not exchangeable) will be included in the description.
Other radial clearance design types are available upon request.

Table clearance for cylindrical roller bearings::

## Cage

High-precision cylindrical roller bearings normally have a roller-guided solid brass cage. In single row high-precision cylindrical roller bearings, PEEK cages can be used upon request.

## Working temperature

SLF’s high-precision cylindrical roller bearings with an outer diameter up to 120 mm are standard stabilized in dimensions by S0, meaning that they are subjected to heat treatment that makes them usable up to a working temperature of 150 °C. At more than 120 mm outer diameter, the cylindrical roller bearings are standard stabilized in dimensions by S1, meaning that they are subjected to heat treatment that makes them usable at working temperatures up to 200 °C. As a rule, however, the maximum working temperature is not limited by the bearing rings’ and rollers’ dimensional stability. Frequently the limitation is the cage or the lubricant. If you are uncertain or have specific questions regarding the maximum temperatures our bearings withstand, don’t hesitate to contact the SLF team.

## Greasing/lubrication & sealing

High-precision cylindrical roller bearings are manufactured without seals. Consequently, the bearing location must be sealed around/ on the surrounding components. The sealing must ensure that no moisture and/ or contaminants can enter the bearing and that no lubricant is lost.

High-precision cylindrical roller bearings are delivered ungreased but must be lubricated with oil or grease. Choose the lubricant according to the application.

## Dimensioning

$$P_r = F_r$$

The bearing lifetime is defined as the number of revolutions or hours before damages to the bearing initially appears. Common reasons for breakdown are wear, jamming, overheating due to overload (mechanical or thermal), and material fatigue. The most frequent reason for failure in the case of high-speed applications is overheating with subsequent jamming of the bearing.
Nominal lifetime of cylindrical roller bearings is calculated according to DIN ISO 281 as follows:


 $$L_{10} = (\frac{C_r}{P_r})^{10/3}$$ $$L_{10h} = \frac{L_{10} * 10^6}{60 * n}$$
 L10 nominal lifetime in million revolutions, with 10% failure probability L10h nominal lifetime in hours, with 10% failure probability Cr dynamic radial load rating [kN] Pr dynamic equivalent load [kN] Fr dynamic equivalent load [kN] n speed [min-1]

$$P_0 = F_{0r}$$

$$S_{0} = \frac{C_0}{P_0}$$
$$P > \frac{C_0}{60}$$