The load carrying capacity and life must be checked for the radial and axial bearing component.

Please contact us in relation to checking of the basic rating life. The speed, load and operating duration must be given.

The static load safety factor S₀ indicates the security against impermissible permanent deformations in the bearing:

In machine tools and similar areas of application, S₀ should be ＞ 4.

The static limiting load diagrams can be used:

• for rapid checking of the selected bearing size under predominantly static load
• for calculation of the tilting moment M_k that can be supported by the bearing in addition to the axial load.

The limiting load diagrams are based on a rolling element set with a static load safety factor S₀ ≧ 4, as well as the screw and bearing ring strength.

The static limiting load must not be exceeded when dimensioning the bearing arrangement. Example: see Figure 1.

The static limiting load diagrams for YRT, YRTS and RTC are shown in Figure 2 to Figure 8.

The static limiting load diagrams for the series ZKLDF are shown in Figure 9 and Figure 10.

The bearings allow the limiting speeds n_G given in the dimension tables. The operating temperatures occurring are heavily dependent on the environmental conditions. Calculation is possible by means of a thermal balance analysis based on frictional torque data.

If the environmental conditions differ from the specifications in relation to adjacent construction tolerances, lubrication, ambient temperature, heat dissipation or from the normal operating conditions for machine tools, checking must be carried out again. Please contact us.

Once the bearings have been fitted and fully screw mounted, they are radially and axially clearance-free and preloaded.

Temperature differences between the shaft and housing influence the radial bearing preload and thus the operating behaviour of the bearing arrangement.

If the shaft temperature is higher than the housing temperature, the radial preload will increase proportionally, so there will be an increase in the rolling element load, bearing friction and bearing temperature.

If the shaft temperature is lower than the housing temperature, the radial preload will decrease proportionally, so the rigidity will decrease to the point of bearing clearance and wear will increase.

The bearing frictional torque M_RL is influenced primarily by the viscosity and quantity of the lubricant and the bearing preload:

• The lubricant viscosity and quantity are dependent on the lubricant grade and operating temperature.
• The bearing preload is dependent on the mounting fits, the geometrical accuracy of the adjacent parts, the temperature difference between the inner and outer ring, the screw tightening torque and the mounting situation (bearing inner ring axially supported on one or both sides).

The frictional torques M_RL in the dimension tables are statistically determined guide values for bearings with grease lubrication (measurement speed n_const = 5 min^–1). Figure 11 shows measured frictional torques for mounting with an unsupported L-section ring for YRT_Speed.

Deviations from the tightening torque of the fixing screws will have a detrimental effect on the preload and the frictional torque.

For YRT and RTC bearings, it must be taken into consideration that the frictional torque can increase by a factor of 2 to 2,5 with increasing speed.

For ZKLDF bearings, it must be taken into consideration that the starting frictional torque can be 1,5 times higher than the values M_RL in the dimension tables.

Axial/radial bearings YRT, RTC and YRT_Speed can be relubricated via the L-section ring and outer ring.

Axial angular contact ball bearings ZKLDF can be relubricated via the outer ring.

The initial greasing is compatible with lubricating oils having a mineral oil base.

For calculation of the relubrication quantities and intervals based on a stated load spectrum (speed, load, operating duration) and the environmental conditions, please contact us.

If the bearing is overlubricated, the bearing frictional torque and the temperature will increase.

In order to achieve the original frictional torque again, the running-in cycle in accordance with Figure 12 should be carried out.

Further information on lubrication in the section link, must be observed.

YRT, RTC, YRT_Speed and ZKLDF have almost the same mounting dimensions.

Geometrical defects in the screw mounting surfaces and fits will influence the running accuracy, preload and running characteristics of the bearing arrangement. The accuracy of the adjacent surfaces must therefore be matched to the overall accuracy requirement of the subassembly. The tolerances of the adjacent surfaces must lie within the running tolerance of the bearing.

The adjacent construction should be produced in accordance with Figure 13 and the tolerances must be in accordance with the tables starting link. Any deviations will influence the bearing frictional torque, running accuracy and running characteristics.

The selection of fits leads to transition fits which means that, depending on the actual dimensional position of the bearing diameter and mounting dimensions, clearance fits or interference fits can arise.

The fit influences, for example, the running accuracy of the bearing and its dynamic characteristics.

An excessively tight fit will increase the radial bearing preload. As a result:

• there is an increase in bearing friction and heat generation in the bearing as well as the load on the raceway system and wear
• there will be a decrease in the achievable speed and the bearing operating life.

For easier matching of the adjacent construction to the actual bearing dimensions, each bearing of series RTC and YRT_Speed is supplied with a measurement record (this is supplied by agreement for other series).

The axial and radial runout accuracy is influenced by:

• the running accuracy of the bearing
• the geometrical accuracy of the adjacent surfaces
• the fit between the rotating bearing ring and adjacent component.

In order to achieve very high running accuracy, the aim should be to achieve as close as possible to a fit clearance 0 on the rotating bearing ring.

The shaft should be produced to tolerance zone h5 and for series YRT_Speed in accordance with the table, link.

If there are special requirements, the fit clearance must be further restricted within the tolerance zone h5:

• Requirements for running accuracy: For maximum running accuracy and with a rotating bearing inner ring, the aim should be to achieve as close as possible to a fit clearance 0. The fit clearance may otherwise increase the bearing runout. With normal requirements for running accuracy or a stationary bearing inner ring, the shaft should be produced to h5.
• Requirements for dynamic characteristics:
  • For swivel type operation (n × d ＜ 35 000 min^–1 · mm, operating duration ED ＜ 10%) the shaft should be produced to h5
  • For higher speeds and longer operating duration 0,01 mm, the fit clearance must not be exceeded. For series YRT_Speed, the fit clearance must not exceed 0,005 mm.

For series ZKLDF, the fit clearance should be based on the inner ring with the smallest bore dimension.

The housing should be produced to tolerance zone J6 and for series  YRT_Speed according to the table Recommended fits, link.

If there are special requirements, the fit clearance must be further restricted within the tolerance zone J6:

• Requirements for running accuracy: For maximum running accuracy and with a rotating bearing outer ring, the aim should be to achieve as close as possible to a fit clearance 0. With a static bearing outer ring, a clearance fit or a design without radial centring should be selected.
• Requirements for dynamic characteristics:
  • For predominantly swivel type operation (n×d ＜ 35 000 min^–1 · mm, operating duration ED ＜ 10%) and a rotating bearing outer ring, the housing fit should be produced to tolerance zone J6
  • For higher speed and operating duration, the bearing outer ring should not be radially centred or the housing fit should be produced as a clearance fit with at least 0,02 mm clearance. This reduces the increase in preload when heat is generated in the bearing position.

If the bearing outer ring is screw mounted on the static component, a fit seating is not required or a fit seating in accordance with the table Recommended fits for adjacent construction, link, can be produced. If the values in the table are used, this will give a transition fit with a tendency towards clearance fit. This generally allows easy fitting.

If the bearing inner ring is screw mounted on the static component, it should nevertheless for functional reasons be supported by the shaft over the whole bearing height. The shaft dimensions should then be selected in accordance with the tables starting on link. If these values in the table are used, this will give a transition fit with a tendency towards clearance fit.

The values given in the following tables for geometrical and positional accuracy of the adjacent construction have proved effective in practice and are adequate for the majority of applications.

The geometrical tolerances influence the axial and radial runout accuracy of the subassembly as well as the bearing frictional torque and the running characteristics.

If the height variation must be as small as possible, the H₁ dimensional tolerance must conform to the tables, link, link and Figure 14.

The mounting dimension H₂ defines the position of any worm wheel used, Figure 14 and Figure 15, L-section ring with support ring.

The L-section ring of bearings YRT and RTC can be mounted unsupported or supported over its whole surface, Figure 15. If the L-section ring is supported, the tilting rigidity is higher. The support ring (for example a worm wheel) is not included in the delivery.

Depending on the application, series YRT and RTC require bearings with a different preload match in order to achieve the same preload forces in the axial bearing.

For series YRT_Speed and ZKLDF, there is only one preload match. The increase in rigidity and frictional torque in YRT_Speed bearings is slight and can normally be ignored.

In bearings of series ZKLDF, the rigidity and frictional torque are not influenced by the support ring.

For the case “L-section ring without support ring”, the bearing designation is:

• YRT ＜bore diameter＞ or RTC ＜bore diameter＞.

For the case "L-section ring with support ring", the bearing designation is:

• YRT ＜bore diameter＞ VSP
• RTC ＜bore diameter＞ T52EB.

For RTC with an additionally restricted axial runout, the bearing designation is:

• RTC ＜bore diameter＞ T52EA.

For bearing arrangements with a supported L-section ring, only bearings with the suffix VSP, EB or T52EA can be ordered.

If the normal design is mounted with a supported L-section ring, there will be a considerable increase in the bearing frictional torque.

The support ring should be at least twice as high as the shaft locating washer of the bearing.

Retaining screws secure the bearing components during transport. For easier centring of the bearing, the screws should be loosened before fitting and either secured again or removed after fitting.

Tighten the fixing screws in crosswise sequence using a torque wrench in three stages to the specified tightening torque M_A, while rotating the bearing ZKLDF, Figure 16:

• Stage 1: 40% of M_A
• Stage 2: 70% of M_A
• Stage 3: 100% of M_A.

Observe the correct grade of the fixing screws.

Mounting forces must only be applied to the bearing ring to be fitted, never through the rolling elements.

Bearing components must not be separated or interchanged during fitting and dismantling.

If the bearing is unusually difficult to move, loosen the fixing screws and tighten them again in steps in a crosswise sequence. This will eliminate any distortion.

Bearings should only be fitted in accordance with TPI 103, Fitting and Maintenance Manual.

The overall rigidity of a bearing position is a description of the magnitude of the displacement of the rotational axis from its ideal position under load. The static rigidity thus has a direct influence on the accuracy of the machining results.

The dimension tables give the rigidity values for the complete bearing position. These take account of the deflection of the rolling element set as well as the deformation of the bearing rings and the screw connections.

The values for the rolling element sets are calculated rigidity values and are for information purposes only. They facilitate comparison with other bearing types, since rolling bearing catalogues generally only give the higher rigidity values for the rolling element set.