Aluminum sand casting for Chenery Gnome Rotary

[albd5a]

Rainbowtronics in Germany can make an Electronic Ignition based on a Hall Effect and there’s a guy in UK who can do a coil system for the spark…. What did you use?
Back to the above: the break terminology was confusing to me. And what makes the Magneto itself spark at the correct time?

With respect to Tap and Die: for External threads is steel, max and min, what diameter to start with, Major Diameter or Pitch Diameter for say, 1”-32 UN ? Thanks.