K4 Locking Nut

The components below show how the K4 is locked using an M10 set screw with spigot extension that extends into the nut which contains 9 holes around the perimeter.

Photo's of the boss will show 8 tapped M10 threads around the rear boss perimeter.

Using the Vernier principle - one of these hole sets will align  every  360º / ( 8 x 9 ) or  5º. So the nut is first tightened with the square drive socket - adjusted a few degrees either way to align a hole set -  then the M10 spigot is tightened down into the aligned hole set and the nut will then remain securely locked.

Additional M10 set screws are then inserted into the remaining 7 threads to keep them clean and ensure balance.

We do not yet have a recorded instance of a K4 unit coming off in service.