Edison Carriage clip screw thread?

[kirtley2012]

Hi All

I'm looking to finally get around to sorting out the last part of my 1897 Edison home I found at an auction a little while ago, that being that one of the carriage clips are missing, I've no problem making the clip, but I'm going to have to make my own screws, which I can do but I'm not sure what thread die I need, anybody know the thread on the early Edison carriage clips?

Thanks