The trunnion is given a shallow hole for the headstock Stebcentre
It is also reinforced with a 6mm bolt which will go through the spigot
The numbers on the spigot can be read through the sighting hole in the trunnion
The assembly is mounted between the headstock Stebcentre and the live centre
The first cut shaves off some of the trunnion, making a useful guide
Then everything is moved round by 72 degrees, ready for the next cut