Quote Originally Posted by Huw Eastwood View Post
Thanks Timothy, can't recall seeing them over here or mention of the ball bearings combined between the pins before, it's an interesting one, cheers.
From Corbin Russwin Cylinder/Keying Parts & Service Manual, earlier versions originally edited by the late Anthony "A.J." Hoffman, pg. 55:
You will find a ball bearing at the bottom of pin stacks in some or all chambers of Corbin and Russwin cylinders manufactured from about 1902 until the mid 1960s. The oldest cylinders have a ball in every chamber. The number of balls was gradually reduced until only the front two chambers had them. The purpose of the balls was to reduce wear on the pins. As harder brass became available, wear became less of a factor, so usage of the balls was eventually phased out.

In my personal experience, I have found that after heavy usage over a period of many years; that the balls often developed a "flat" at the point where they met the top pin. This slight amount of wear could make the key more difficult to turn since the pin was then a tad below the shear line due to the slightly reduced diameter of the ball.

Pete Schifferli