About this detail of the Tiger
The Tiger's mantlet was supported by trunnions embedded in the turret walls. This cutaway diagram, extracted from the Turret Manual, shows the left side of the mantlet. It has a bearing hole where a trunnion can be inserted.
As you can see, the rear side of the bearing can be removed; this was done only to separate the mantlet from the turret.
Seen from inside a Tiger (at Saumur museum), this is the left-hand mantlet bearing. This vehicle is a 'late' Tiger. In the earlier Tigers with deep-wading abiity, the bearing was not visible; it was covered by the a waterproof sealing frame.
Notice that the end of the trunnion can be glimpsed between the bearing and the main body of the mantlet.
This diagram shows the removable half of a trunnion bearing.
The two large bolts were embedded within the bearing cover, and had female heads. The locking mechanism allowed them to be fixed at any multiple of 20 degrees. All of the large bolts on a Tiger had anti-vibration locks, but this is the most complex one that I am aware of. The small fixing screw is unique.
The bearing cover has two small items at the outer corners, apparently dowels, to aid in aligning it.
This German diagram, extracted from the Turret Manual, shows a section through a bearing. One of the large fixing bolts is visible, with its locking device.
Within the bearing there is a spherical steel bushing, labelled 'Buchse'.
This is a model of the Tiger's bushings. Each consisted of an inner sleeve and an outer spherical housing. The Pz4 had a similar arrangement, and its inner sleeves were made of brass, so I assume the same material was used here.
This diagram shows the dimensions of a Tiger bushing.
This model of a turret, with the mantlet removed, shows a bushing placed upon its trunnion. The small item to the right is a filling tap for lubrication grease for the bushing. They were originally painted red, as shown in the model.
These filling taps are numbered (45) on the Tiger Lubrication Chart. They should be filled with grease "every two to three months".
This is a view of the same model from the front, showing the bushing and the outer end of the trunnion, which also serves as a lifting lug for the turret.(The latest version of this article)