Post a pic of the other (non stud) end of the pedal. If the cap has sides you can throw an adjustable on it and crank the cap off, then pull the rest of the bearing assembly apart. If the cap doesn't have sides or is crimped into the pedal frame, I'm lost. Also, make sure the pedals are about the same length before you go pulling them apart. The threaded bit is the end of an axle that runs the length of the pedal. I'm pretty sure I saw somebody somewhere that sold adapaters for 9/16" to 1/2" Maybe it was the other way?