Duplex bearings are two matched bearings which provide the following bearing characteristics:
· accurate bearing positioning in radial and axial directions
from a defined clearance to controlled rigidity.
· limitation of the yield of the system.
· higher load capacity compared to a single bearing.
The matching of the bearings is achieved by loading each single bearing with the desired preload and then relieving the inner and/or outer rings until the surfaces of both rings are flush with each other.
Two bearings machined in this way are assembled according to their markings and the instruction on the package, and loaded axially with the specified or required force. Depending on the matching used, either the inner rings or the outer rings, or even both rings are clamped together.
The ball bearings must be mounted in accordance with the installation instructions on the packaging labels or the marks on the ball bearings.
Deep groove radial bearings:
Unless specified otherwise by the customer, GRW matches deep groove radial bearings with a preload of 5 N and a nominal contact angle of 15°. On request, preload and contact angle can be adjusted to customer's individual operating requirements. For Duplex bearings, radial clearance should be selected higher than normal to achieve a greater contact angle, rigidity, and axial loading.
The preload and the contact angle are generally specified for spindle bearings. The standard contact angle is 15° (C) or 25° (E), preload is grouped in light (L), medium (M) and strong (S). On request, preload and contact angle can be adjusted to customer's individual operating requirements.
However, the preload should not set higher than required as this would result in an unnecessary increase in torque, which in turn would directly affect the lifetime of the ball bearing. To achieve, as far as possible, an identical fit for both ball bearings, Duplex ball bearings are usually graded into 2 groups each on the bore and outside diameter and supplied packaged in pairs with the same code. If possible, they should also be mounted with graded shafts and housings. The ball bearing fits should therefore be selected carefully because an interference fit at the inner or outer ring would change the preload.
The following types of Duplex assembly for deep groove radial ball bearings and spindle bearings are available:
- O arrangement: Back to back (pairing type -1 or DB with spindle bearings)
- X arrangement: Face to face (pairing type -2 or DF with spindle bearings)
- Tandem arrangement (pairing type -3 or DT with spindle bearing)
- Universal (pairing type -4 or DU with spindle bearings)
Where highest rigidity is required, bearing sets comprising several bearings can be used. Depending on the application, these bearing sets are made up of universally paired bearings in X, O, or tandem arrangement.
For more information about duplex assembly and bearing sets take a look at our catalogue.