SPERICAL BEARING: Why there is a gap in the outer ring?
Spherical plain bearings are essential components in many industrial and mechanical applications because they allow smooth movement and full freedom of rotation, especially in those contexts where high performance and precision are required.
A common detail found in spherical plain bearings is the presence of a slot in the outer ring. But why exactly is this gap present?
The main reason for this slot is related to the assembly of the spherical plain bearing. This is specially created to allow the outer ring to open under the thrust of the kneecap during the assembly of the two components; once the kneecap has entered its seat, the outer ring closes again.
The outer ring is able to withstand this elastic deformation after undergoing a hardening heat treatment.
This treatment of the outer ring is a very delicate step, as the outer ring must not be too brittle, to prevent it from breaking during assembly, but at the same time it must not be too malleable, to prevent the outer ring from cracking once assembled.
A slight crack in the outer ring, in the order of 1 to 2 mm is acceptable, and is not to be considered a defect. If, for example, you take a spherical joint whose outer ring is cracked by a couple of millimetres and try to check the axial or radial play, you will see that these are particularly high.
It may happen to find spherical plain bearings with a 2-piece outer ring, held together by small springs; this layout is usually used on large spherical plain bearings and in self-lubricating versions.
