The insert with a spherical outer ring matching the hollow spherical housing compensates for static misalignments of the shaft. Mounting on the shaft is by means of locking screws (set screws/ grub screws), eccentric ring (eccentric clamping ring) or adapter sleeve. The materials used are cast iron, stainless steel, pressed steel or thermoplastic.


The deep groove ball bearings are sealed with a rubber seal. In the case of the UC (mounting on the shaft with locking screw) and UK (mounting on the shaft with adapter sleeve) versions, flinger rings made of sheet steel are attached to the inner ring of the bearing and thus protect against the ingress of dirt.


Besides our own bearing units of the brand ASK we have the bearing units of the Japanese brand ASAHI in our product range. The CAD data of the brand ASK is available on the product page. The CAD data of the ASAHI brand can be obtained from the ASAHI homepage. The CAD data contains the housing and the insert.

Areas of application

Bearing units offer countless application options for a wide range of bearing arrangement concepts. The product range includes various series and housing forms such as pillow blocks, two-bolt flanged bearing units, three-bolt flanged bearing units, four-bolt flanged bearing units, flanged cartridge units, take-up units and cartridge units.

Technical basics bearing units

All bearing units consist of a housing and a built-in ball bearing (inserts).  The housing is available in various designs. The ball bearing has a spherical outer ring. The seating in the housing is suitably hollow-ball shaped. The ball bearing is firmly seated in the housing of the ASK bearing units and less firmly seated in the housing of the ASAHI bearing units. Accordingly, more force is required to tilt the ASK inserts in the housing.  Misalignments can thus be compensated for within certain limits.


Housing materials

Standard: Cast iron JIS FC200

Stainless steel (Niro): JIS SUS304

Thermoplastic: PBT thermoplastic

Silver series: Zinc die-casting

Silver-Niro series ASK: Stainless steel

Silver-Niro series ASAHI: Zinc die-casting with nickel chrome plating

Pressed series: Pressed steel

Cast iron and stainless steel materials are predominant.

Housing types


Pillow block

Flanged bearing units

Take-up units

Inserts are displaceable. They are used for shafts that are swiveled or displaced. Combined with a UC insert, this becomes, for example, a UCT 204.



Cartridge are used like rolling bearings and can be fixed to the shaft with set screws as locking screws. Combined with a UC insert, this becomes a UCC 208, for example.


Possible combinations

of housings and inserts 


Operating temperature

The temperature of the unit must be between -15°C and 100°C during operation.



Bearing units are filled ex works with a standard grease for rolling bearings. Small quantities of grease may leak out during commissioning. It is advisable to remove the leaked quantities.


Relubrication must be carried out using a suitable grease gun. Grease must be pressed in until a small amount of grease escapes at the seal. Caution: In the case of central lubrication systems, the pressure may have to be reduced before the grease enters the bearing, otherwise the covers and seals may be damaged.

It is advisable to lubricate the bearing before longer standstills. After lubrication, run the bearing briefly and remove any escaping grease.

Relubrication intervals

It is not possible to make a general statement about the inspection and relubrication intervals, as they depend on many influencing factors, such as ambient conditions, dust, dirt, direction of rotation, load, temperature, etc., but also on the damage that can be caused by a failure. If no empirical values are available, the check should be carried out daily and before each start-up after a standstill.


For the lubrication of rolling bearings, corrosion-protective lithium-based pressure-resistant greases or lithium-complex metal soap greases have proven effective. When selecting the grease, please also consider the operating temperature range of the bearings. The manufacturers of the greases can advise you in individual cases.


of the ASK housing units

Radial clearance for bearings  (inserts) ( unit 0,001mm)

Bore diameter with cylindrical bore ( unit 0.001mm)
(Inserts with set-screw locking screws or eccentric collar locking)

Bore diameter with tapered bore ( unit 0.001mm)
(Inserts with adapter sleeve locking)

Mounting the shaft

for ASK bearing units

Recommended fits

The diameter of the shaft must be adapted to the bore. A shaft that deviates greatly in diameter would cause out-of-round running. Vibrations and premature failure of the bearings could be the result. The fits we recommend are based on experience under normal operating conditions. In case of strong deviations, e.g. due to uneven temperature distribution or high elastic deformation, this must be taken into account accordingly by adjusting the tolerances.

It is also important to consider the elongation of the shaft. In order to avoid high axial pressure on the bearings, a bearing must be designed as a non-locating bearing in such cases.


Recommended fit for bearings with cylindrical bore

For bearing units with cylindrical bore (with set-screw locking or eccentric collar locking), a loose fit is usually used. Our recommendation for shaft tolerances for this case can be found in the following table.

For high speed or very precise applications or when shock loads occur, an interference fit should be used. The following table shows the shaft tolerances. When using inserts with eccentric collar locking and interference fit, the eccentric rings can be omitted.

Recommended fit for bearings with cylindrical bore

Housing bearings with a tapered bore allow larger tolerances, since the shaft is secured to the by means of the adapter sleeve. The recommended shaft tolerances can be found in this table.


Fixing the shaft with set-screw locking

For normal applications, it is sufficient to fasten the housing units to the shaft using the locking screws. It is recommended to flatten or lower the shaft at the contact point to achieve an even better fit.

In case of vibrations or shock loads, a shaft with shoulder can be used. Please ensure that the locking screws are tightened sufficiently.

Flattened shaft                                                Shaft lowered                                                   Shaft with shoulder


Tightening torque for bearings with locking screws


Length compensation for thermal expansion

If bearing units are firmly connected to the shaft either with set-screw lockings, adapter sleeves lockings or eccentric collar lockings and a thecrowned outer ring is fixed in the housing, length compensation is only possible to a limited extent. In cases where the distance between the two bearings and the length of the shafts behave differently, the axial pressure on the ball bearings may become too high. If one of the two bearings is a floating bearing, this can be ruled out.

Different elongation is possible at high temperatures, at high temperature differences between components or at large distances between the housing units.

In these cases, it is advisable to design one bearing as a locating bearing (taking on radial and all axial forces) and the other bearing as a non-locating bearing (taking on radial forces only).

In the case of the locating bearing, the housing unit is firmly connected to the shaft. The other housing unit is used as a non-locating bearing using a SH screw. The groove in the shaft allows the housing unit to compensate for linear expansion. If the SH screw is used, we recommend a shaft tolerance of h7 or h8.

The same effect is achieved by using a cylindrical housing:

Floating bearing with SH screw and groove in the shaft                                           Cylinder housing


Requirements for the mounting surface

The surface on which the housings are screwed must be flat (machined) and free of paint or dirt. The screws must be positioned so that they are at a distance from the walls of the through hole of the housings. If the housings are screwed onto an uneven surface with great force, the stresses in the housing can become so great that the housing breaks.



Bearing units can be used to compensate for misalignment to a small extent.

The following values should not be exceeded:



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Bearing units