1/4-20 Square Nuts

I wonder why Ford used 1/4-20 square nuts 7/16 across the flats on the early T’s, but later switched to 1/2 across the flats? It goes against everything I’ve learned about Model T’s. In addition, I’ve never thought of researching this topic while at the Ford Archives. I’ll have to do that sometime.

From AFE 20-89041, dated April 08, 1920:

“Square nuts of 1/4” and 20 threads per inch with a 1/2" flat face shall be
used henceforth for no other reason than to baffle future restoration hobbyists."


Good one Raoul!

Is it possible that the industry standard simply changed and Ford changed along with it to prevent having to pay a premium for “special”, non-standard nuts?

Yes, but why can you only buy a 7/16 square nut today, other than Randall Anderson, who makes the correct 1/2 version.