I have the distinct impression that the mechanics of a gun lock is rather a mistery to you, and may be best left too someone who more knowledgeable to remove the bearing ware. Just to make clear things clear, the hammer is fitted to a rotating shaft one shaft bearing is the lock plate its self with reasonable quality locks the bridle is the bearing for the other end of the shaft, with the tumbler permanently fitted to the shaft situated between the internal side of the lock plate and the bridal. Because of the force applied to the shaft by the main spring acting on the tumbler the holes in the lock plate and bridal over time ware also the bearings on the hammer shaft ware to some extent. To remove this ware in the bearing holes shims can be fitted, this being the quickest and simplest way.
To fit a slim metal bearing in to each of the holes it becomes a highly skilled job. I would go in to how that is done but I feel that few people have the required lathe to make said new bearings and the press to fit them because they have to be interference fit to make a high class job, also it is extremely difficult to fit bearings whose walls are fifteen thousands of an inch thick. Also a lathe is needed to skim the shaft bearings back to round then polish and burnish them.
