Take the bolt to your local Lowes store,they have a board in the hardware
dept.that will tell you the size of what you have,go to the Kolbalt rack for
their taps get the size that fits your bolt,buy the tap and run it in and
clean you hole up,check bolt to make sure that its ok and put her back to
gether,worked on my Parker when I ooops!
Your problem may not be cross-threading. It's possible you didn't loosen the main assembly bolt setscrew, and you just see the marks where the setscrew hit the main assembly bolt as you took it out - just a thought!