Here is a great post about that:

http://arcadecontrols.com/BBBB/wc.html

My experience so far is DON’T use a metal Allen wrench.

Out of the three times I have attempted this method I have destroyed the core inside two of them.

One out of three success is not good so I have purchased the proper tools.

I bought a tool set of 4 different sizes here for about $30 shipped:

https://www.arcadepartsandrepair.com/store/tools-supplies/tools/delrin-television-width-coil-alignment-adjustment-tool-set-4-piece-set/