Cylindrical Roller Bearings

Listing ID #4344856

Cylindrical roller bearings are manufactured in a various range of constructive types and sizes, particularly single row cylindrical roller bearings but also two or more row cylindrical roller bearings, with cages or roller by roller, as shown in the designs below.

In case of cylindrical roller bearings, the rollers are laterally guided by the fixed ribs of one ring.

In case of bearings with cages, the ring with ribs and the rollers retained in the cage can be drawn out from the other ring, which means that these bearings are dis-mountable  Therefore, bearings from joints can be much easier mounted and dismounted, especially were interference fits are needed for both rings due to the loading condi-tions. Bearings are provided with unloaded rollers at both generatrix ends. Therefore, the linear contact between rollers and rings alters advantageously, i.e.peripheral stresses are avoided.

Single or more rows cylindrical roller bearings

Single row cylindrical roller bearings are manufactured by MTK+ in various constructive versions, depending on the position of the ribs on rings. The four basic designs (NU, NJ, N and NUP) are given in the bearing tables Bearings of NU design have two fixed ribs on the outer ring and one smooth inner ring. Bearings of N design have twofixed ribs on the inner ring and one smooth outer ring. These designs allow an axial displacement in certain limits, of the shaft in relation to the housing. Therefore, these rolling bearings are used in non-locating bearing units. Bearings of NJ design have two fixed ribs on the outer ring and a fixed rib on the inner ring which can guide the shaft in a single direction (axially).Bearings of NUP design have also two fixed ribs on the outer ring and, on the inner ring, a fixed rib and a support washer. This way they can be used as locating bearings, guiding the shaft axially in both directions.For a shaft guiding in a single direction, it also can be used a bearing of NLJ design which is combined with a support washer. Thus, the constructive version NUJ is obtained Support washers on both sides of a bearing of NU design are not allowed as they lead to an axial blocking of the rollers.

Cylindrical roller bearings can carry heavy radial loads and can  operate at high speeds.

Double or more rows cylindrical roller bearings have small sections, high load carrying capacity and stiffness.

These bearings provide high stiffness and maximum load carrying capacity and are particularly used for tool holders of the machine-tools and rolling mills.

Double row cylindrical roller bearings series NNU49 and NN30 are generally manufactured to tolerance classes P5 and SP, used for machine tools.

Large-sized bearings series NNU49 are also manufac-tured to the normal tolerance class.

Cylindrical roller bearings with snap ring groove

Single row cylindrical roller bearings are also manufac-tured with snap ring grooves on the outer rings. This design simplifies the bearing joint as the bearings are located into the housing by means of the snap rings. The snap ring groove and snap rings are in accordance with ISO 464, and tables 7 and 8 on page 84 and 87.

Cylindrical roller bearings without cage (full complement)

These bearings incorporate the maximum number of rollers and have a small section in relation to their width.

This provides a high load carrying capacity and allows space-saving designs to be achieved.

Cylindrical roller bearings without cage cannot be used at speeds as high as those with cages. These bearings are manufactured with single or more row rollers and suffix V is added to the bearing designation. The most utilized bearings are those of series NCF29 V, NCF30 V and NJ23VH and they are given in this catalogue on page 194.M

Dimensions

The main dimensions of standardized bearings given in tables are in accordance with ISO 15.

Misalignment

The modified contact between rollers and raceway al-lows not only peripheral stresses to be avoided but also, in case of single row roller bearings, permits an angular misalignment of the outer ring with respect to the inner ring, depending on the bearing series and load according to the table 1.

Tolerances and radial clearance

Single row cylindrical roller bearings are usually manufactured to normal tolerance class with normal radial clearance

They can also be manufactured to more accurate tolerance classes and with larger (C3NA and C4NA) or smaller (C1NA and C2NA) radial clearances.

Tolerances of cylindrical roller bearings are given on pages 24.

Radial clearances according to international standard ISO 5753 are given in tables 2 and 3 for cylindrical bore bearings both with interchangeable rings and with non-interchangeable rings (NA).

Cages

Small and medium-sized single row cylindrical roller bearings are generally fitted with pressed sheet cages. Large-sized bearings are fitted with machined brass cages of normal design, i.e. cages of separable design guided on rolling elements M, on the outside surface MA or inner surface MB.

In case of heavy loads and high speeds, cages are made in one piece.

Glass fibre reinforced polyamide 6.6 cages, are suc-cessfully used for small and medium-sized bearings, if the operating temperature doesn’t exceed + 120?C. These cages have low weight, low coefficient of friction and are noiseless while running.

Cage design and some technical data are given in table 4.

Minimum load

Cylindrical roller bearings must be subjected to a given minimum load, so that a proper operation of these bear-ings can be guaranteed.

This is necessary especially as the bearings are operated at high speeds and the centrifugal forces produce additional friction in bearing due to the sliding between rollers and raceway.

The values of the minimum load can be enough ac-curately calculated using the equation:

Frm = 0,02 Cr, kN;

Minimum load

For cylindrical roller bearings purely radially loaded which don’t locate shafts axially, equivalent dynamic load is:

Pr = Fr, kN;

If cylindrical roller bearings have ribs on the outer and inner rings and locate shafts axially in one or both direc-tions, equivalent dynamic load can be calculated using the equations:

The viscosity ratio k is the ratio of the actual viscosity at the operating temperature to the requisite viscosity for a proper lubrication at that temperature. Further details can be found in subchapter “Adjusted rating life”, life adjust-ment factor a3 – on page 20.

In case of grease lubrication, the base oil viscosity of the grease should be used. These effects can be reduced at low speeds by using oils with EP additives.

The values of permissible axial load Fa max obtained from the equation above mentioned are valid for a con-tinuously acting constant axial load. If axial loads act only for short periods, the values may be multiplied by 2 or for shock loads by 3.

The constantly acting axial load Fa max (N) should never exceed the numerical value of 1,2 D2( D= bearing outside diameter, mm) and occasional shock loads should never be greater than the numerical value of 3 D2.

In case of heavy axial loads (Fa > D2 ), the ribs of the outer and inner ring respectively are recommended to be supported by the bearing adjoint parts. Bearings of NUP and NJ+HJ designs which take axial loads in both direc-tions are to be placed so that main axial loads should be taken by the fixed ribs, if bearing design allows.

Heat treatment

Cylindrical roller bearings with outside diameter D > 240 mm of all series given in the catalogue are to be subjected to a heat treatment of stress relieving which allows bearings to be operated up to a temperature of +150?C.

The hardness of rings should not be less 59 HRC.

Small-sized bearings operate normally up to +120?C.

Abutment dimensions

For a proper location of bearing rings on the shaft and housing shoulder respectively, shaft (housing) maximum radius ru max should be less than bearing minimum mounting chamfer rs min.

Shoulder height should also be properly sized in case of bearing maximum mounting chamfer.

The values of the connection radii and support shoulder height are given in table 6.

Abutment dimensions for single row cylindrical roller bearings are given in table 7. The values for double row cylindrical roller bearings are given in table 8.