Is Drive Flange Bolt Witworth?

[BGGB]

Hello all, i'm in the process of rebuilding a 69 bugeye and am getting the axles back together. when i went to install the drive flange bolts they went hard and i ended up snapping one off inside the threaded hub end(my fault, i should have known). anyways i pulled the drive flange back off and notice that all the threads inside are rusted and in bad condition, this is due to that fact that when i bought it years ago the original owner took the flanges off and it sat without for XX years, allowing the elements to them. anyways when i got out the thread chaser set i couldn't find one that matched the thread correctly, it seems an odd size. im getting 20 threads/inch and a diamerter of .375. a 3/8 bolt is .372 i believe but only comes in 16 or 24 thread. is this a witworth size...? what should i do to clean up the threads. i did take a bolt from another rover to make sure i didn't switch up the bolts on accident. also the bolt that im using reads TWL T-BSF if that means an anything.
Thanks for any help, Glenn

[slorocco]

BSF => British Standard Fine threads. It is different from the modern standards but I'm not sure of it's the same as witworth.

[yorker]

http://www.landroverclub.net/Club/HTML/Whitworth_BSF_BA.htm

[greenmeanie]

Be careful to read up on grades as well. BSF has different notation from metric or UN fasteners but as always strength is important.

[BGGB]

i found a BSF 3/8-20 tap/thread chaser....hopefully ill be able to clean up the threads and use the orginal bolts. Thanks guys