"When I use the set, pulling the hair goes down from full to half. "
Sorry, but can you try that again??? I don't know what "pulling the hair" means.
The FLY in a lock works every time you pull the trigger on the gun at full cock. It doesn't matter if you first set the trigger, or don't use the set trigger. The Fly simply allows the sear to rotate OVER the half-cock notch as the hammer is falling when the gun is fired. The Fly moves up and out of the way, as the hammer is cocked, to allow you to let the sear nose enter the half cock notch. This movement occurs with and with out the trigger "set" being used. A trigger "set", or " set trigger", only works on the trigger(s), not the tumbler or Fly. They are separate, and distinct parts and functions.
Now, YOU CAN only move the FLY out of the way to put the sear at half cock, by lowering the hammer all the way down, past the half cock notch, and then cocking the hammer slightly past it. If you cock the hammer back to full cock, the fly will fall back into its normal place, and block the sear from entering the half cock notch.
There should be a small "click" heard and sometimes felt when the FLY is moved back out of the way of the half cock notch, when the hammer is slowly cocked back. That "click" tells you that you can now lower the hammer into the half cock position. :hmm: :thumbsup: