Centering a punch mark in the 4-jaw

[krv3000]

hi well in my post on me air engine one way is to use a needle in a tale stock chuck the other one that I have is a wobbler I will have to get a pic of it and post but the way it works is it goes in the tool post it consists of a gamble and a long rod with a point at both ends one point goes in the pop Mack  turn the lathe chuck by hand and the other end will run of centre keep adjusting the parte until the rod says still