The decisive factors in determining the bearing size are the basic rating life, the static load safety factor and the axial limiting load. The basic rating life L and L_h are calculated as follows:

The easy-to-use static limiting load diagrams allow quick verification of the bearing size of series ZKLR, as a function of the axial and radial operating load, Figure 11 to Figure 13. The decisive requirement is that the intersection between the axial and radial load must be below the limit line.

Example: If the operating loads F_a and F_r are below the limit line, the bearing size is suitable for the application, see example Figure 13.

The bearings are axially preloaded to a defined value if the recommended precision locknuts are used and the correct nut tightening torque is applied. The resultant axial bearing load F_a res is determined from the axial operating load F_aB and taking account of the axial preload according to Figure 1, to Figure 5. For 7602, 7603 and BSB, the F_a res diagrams are based on two-bearing sets in an O or X arrangement, see link. For calculation of other set combinations, please contact us.

A load in excess of the limit value will lead to the rolling element row without load lifting off the raceway. As a result, higher wear will occur under rapid acceleration. For extreme moment loads and statically overdefined systems (locating/locating bearing arrangements), please contact us. The calculation program BEARINX^® can give a precise design in this case.

Under purely axial load, P = F_a res. If additional radial operating loads are present, P must be calculated as follows:

The values X and Y are given in the following table.

In this case, P and n are calculated as follows (q = time portion %):

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

In machine tools, S₀ should be ≧ 4.

If bearings of series ZKLF are screw mounted on a flat adjacent construction, the maximum radial load that can be supported by the screw connections must be taken into consideration.

If the screws used are as stated in the dimension tables to DIN EN ISO 4 762, the maximum radial load that can be supported before the outer ring moves, in the case of dry components, is restricted to ≈ 0,1×C_0a. If the outer ring is additionally bonded in place using, for example, Loctite 638, the maximum radial load that can be supported increases to approx. ≈ 0,5×C_0a.

If the maximum radial loads that can be supported (without any axial load content) are considered in relation to the rolling element set, it can be seen that:

• With a static load safety factor of S₀ ≧ 4 as required for machine tools, the load that can be supported by the screw connections of the outer ring is in any case greater than the radial load as restricted by the rolling element set.

This means that (at least in theory) radial loads can be supported that, in relation to the rolling element set, will lead to a static load safety factor of S₀ ≦ 1 (incipient plastic deformation of rolling elements), if the outer ring is additionally bonded in place.

This means that, under normal design criteria and with the decisive static load safety factor for the corresponding areas of application (e.g. S₀ = 4 for machine tools), the rolling element set is always the decisive criterion.

For bearings of series ZKLF, the permissible static axial load in the direction of the screw connections, Figure 14, is:

The basic static axial load rating C_0a is stated in the dimension tables.

The adjacent construction (the shaft and housing) must be designed in accordance with the data in the dimension tables.

The abutment diameters for the shaft and housing shoulders d_a and D_a must be in accordance with the dimension tables.

D_a and d_a are recommended minimum abutment diameters. If these values are not used, the rib diameter d₁ according to the dimension table must be observed.

In matched bearing pairs of series ZKLN and ZKLF, the depth of the housing bore must be defined such that the outer ring of the outermost bearing is radially supported to at least 1/4 of its width.

The limiting speeds n_G given in the dimension tables are based on the following conditions:

• bearing preloaded, no external operating load
• operating duration 25%
• max. equilibrium temperature +50 °C.

Under favourable environmental influences, a bearing with gap seals (suffix 2Z) can be used instead of contact seals. The limiting speed of these bearings is approximately twice that of axial angular contact ball bearings with contact seals.

In most applications, preloading of bearings by means of the locknut tightening torque gives sufficiently accurate setting values. The reference here is the tightening torque M_A according to the dimension table in conjunction with an INA precision locknut.

The frictional torque M_RL given in the dimension tables is a guide value. The frictional torques are based, for bearings of series ZKLN, ZKLF, ZKLFA, DKLFA, 7602..-2RS, 7603..-2RS, BSB..-2RS and ZKLR on grease lubrication, measured at a speed of n = 5 min^–1.

For unsealed bearings of series 7602, 7603 and BSB, the frictional torque M_RL is based on lightly oiled raceways.

For dimensioning of the drive, the starting frictional torque and the frictional torque at high speeds of 2 to 3×M_RL must be taken into consideration.

In axial angular contact ball bearings with contact seals (suffix 2RS), the extent of seal friction must not be neglected. Sealing influences the limiting speeds.

The frictional energy N_R of the bearings can be calculated as follows:

In any analysis of the thermal balance, the various operating speeds n_i and their corresponding time portions q_i must be taken into consideration.

Bearings for screw drives can be lubricated with grease or oil. In machine tools, however, the mean bearing temperature should not exceed +50 °C. If this is the case, a lubrication method without heat dissipation such as grease lubrication or oil impulse lubrication can be selected.

For higher bearing temperatures and open bearings, recirculating oil lubrication should be used.

Bearings with a relubrication facility of series ZKLN, ZKLF, ZKLFA and DKLFA are greased with a lithium soap grease to GA28 and are preferably run with grease lubrication. In most cases, the initial greasing is sufficient for the whole operating life of the bearing.

Under certain application conditions, re­lubrication may be necessary. In this case, Arcanol MULTITOP is suitable. The initial greasing is compatible with greases with a mineral oil base­.

For checking by calculation of the grease operating life or relubrication interval, please contact us.

The relubrication intervals cannot be determined precisely in advance. They are essentially dependent on the operating conditions and the environmental influences such as temperature, contamination, dust, water, etc.

Bearings must always be relubricated:

• before and after long stoppage periods
• in conditions of high humidity
• within the defined lubrication intervals as stated in the technical proposal letter.

For the following conditions, please contact us:

• if the bearings are stationary
• if vibration is present
• if very small oscillating movements occur.

If bearings of series ZKLN, ZKLF, ZKLFA and DKLFA must be relubricated due to the application conditions, please contact us regarding the relubrication quantities.

Other lubrication methods such as oil impulse lubrication or recirculating oil lubrication are also possible. For oil lubrication, good results have been obtained with oils CLP to DIN 51517 and HLP to DIN 51524 of ISO-VG 32 to ISO-VG 100.

If oil impulse lubrication is intended for series ZKLN and ZKLF, gap seals are advantageous. They prevent contamination entering the bearing and allow oil to leave the bearing. This prevents overlubrication.

Bearings should only be fitted and dismantled in accordance with the Fitting and Maintenance Manual TPI 100. This TPI is available upon request.

During fitting of bearings, mounting forces should be applied only to the bearing ring to be fitted. Mounting forces must never be directed through the rolling elements or sealing rings.

The characteristics of the bearings are only valid when used in combination with INA precision locknuts and the associated tightening torques given in the dimension tables.

Axial angular contact ball bearings are self-retaining and the individual bearing components are matched to each other. The inner rings must not removed from the bearing during fitting and dismantling. If individual bearing components are removed from the bearing, please contact us before carrying out any reassembly.

Axial angular contact ball bearings ZKLN, 7602, 7603 and BSB must be located clearance-free in the housing and on the shaft and must be axially preloaded during fitting. The axial preload force must be distributed evenly over the circumference in order to avoid deformation of the raceways.

Outer rings are axially tensioned to the preload force given in the dimension table by means of a ring nut (not supplied), Figure 15. Secure the ring nut against loosening (using, for example, Loctite 638).

Ring nuts with a runout of max. 5 μm apply the preload force evenly over the bearing rings and should therefore be used in preference to location by means of a cover.

Clamping of the outer rings using a cover and cap screws leads to deformation of the raceways, Figure 16. In order to minimise the deformation and achieve the calculated life:

• the cover should be designed with adequate rigidity
• the number of fixing screws should be selected in accordance with the load but at least four should be used
• the screws should be tightened in a cross-wise sequence in four stages (finger tight, 40%, 70%, 100% of M_A).

Observe the axial preload force in the dimension table. If other values are used, this will influence the bearing preload, bearing friction and heat generation in the bearing position.

Axial angular contact ball bearings must be axially preloaded during fitting by means of a precision locknut.

When preloading the bearings by means of the bearing inner rings using the recommended precision locknut, the tightening torques given in the dimension tables must be observed. The tightening torques for the individual bearing sizes are only valid for the INA precision locknuts listed.

The preload force for series DKLFA is determined specifically on the basis of the operating conditions (load spectrum). Please contact us.

In order to counteract settling, it is recommended that the locknut should initially be tightened to twice the tightening torque M_A and then relieved of load again. It should only then be tightened again to the stated tightening torque M_A. Finally, the precision locknut should be secured against rotation by the torque-controlled tightening of the grub screws.

The characteristics of the bearings are only valid if the preload forces specified in the dimension tables are observed. The tightening torques for INA precision locknuts re­quired for this purpose are also given in the dimension tables.

If other suitable locknuts are used, the manufacturer’s guidance on calculation of the necessary tightening torque should be observed.

Only locknuts with a minimum runout accuracy of the end face to the thread of 5 μm should be used.

The fixing screws for the outer ring must be tightened in a crosswise sequence. They may be loaded up to 70% of their proof stress.

If the bearing outer ring is supported by an additional housing cover, it must be ensured that the fixing screws are sufficiently well dimensioned.

Angular contact ball bearing units ZKLR require no additional preload after fitting. They can often therefore be located on the spindle simply by means of clearance-free clamping.

The type of axial location depends on the load to be supported.

The adjacent construction can be a milled flat face or, if necessary, even an unmachined screw mounting surface without radial centring.

Locate the bearing unit using a locknut  or clearance-free clamping on the threaded spindle , Figure 17.

Screw mount the bearing unit on the adjacent construction; tighten the screws only finger tight .

Move the screw drive nut  towards the bearing unit (the position of the screw drive is the datum for the linear guidance system, the nut serves as a functional element for alignment). The bearing will align itself to the optimum radial position (due to the constraining forces exerted by the datum).

Screw the bearing unit to the adjacent construction using the tightening torque specified in the assembly drawing .