Schwinn springer pivot bolt thread pitch

[Mymando]

Does anyone out there know what thread pitch Schwinn used on the late 50’s springer pivot bolt for the fork legs? I want to get a tap to chase the threads on the fork legs and not sure what the thread pitch is? Any help would be greatly appreciated! Thanks

 

[Schwinn lover]

Bicyclebones sells these for $18.00$ but if you only want to tap the threads ,, we'll here it is