Razor back thread size?

[DJackson]

So I have pre 65 razor back stem that should clean up nicely if I can fix the clamp bolt. I was thinking I can drill it and Chase the original threads, does anyone know what thread pitch is original?

 

[49autocycledeluxe]

probably has goofy threads if it is Schwinn. I say give it a few good soaks in PB Blaster and remove it with a pair of vice grips.