I have a solid walnut steering wheel for my '26, including the spider. It has a iron hub which uses 8 bolts to hold everything together. The bolts I thought were 1/2" head. When I tried to use a wrench, it was just a hair to small, thought that was strange for it's age didn't think they would use metric back then. I tried a 14mm wrench and it was to big. I measured the head and across the flats of the head and it was .520". I checked a couple other bolts all the same. There is a label on it saying it was made in Chicago. Is anyone aware of bolts that size? Thanks
Whitworth 1/4 (or 5/16)... comes from having too much British rust, the heads are just over 1/2", if it's not 13mm that's what I'd try...
Just looked it up. 13mm is .511", 1/4W is .525"
There ya go (and Bob's your rusty uncle!
It may be 17/32. Many years ago there were weird in-between sizes like that. I have a few wrenches in those strange sizes.
We had a 1913 Cadillac for many years and most of the bolts of differing sizes had 13 threads to the inch. I believe that the larger bolts were made by Cadillac and they simply had their lathe's thread cutting attachment set at 13. That steering wheel could be off of an English car. and Susanne could be right with her bubble and squeak. (and Bob's your rusty uncle!) indeed !
For many years Craftsman wrench sets included odd sizes like 17/32 and 25/64. I haven't run across any modern vehicles 1950 or newer with these size bolts, but old cars like out T's and others have them.
I purchased the bulk of my Craftsmen tools
prior to going up on the North Slope to work on the Alaska Pipeline in 1975 - my wrench sets have those oddball sizes - still have them !
You will need to get an American adjustable wrench for that nut.
While your at it you should get the metric and Whitworth versions also.
A metric adjustable will work in a pinch.
They are still available. Check McMaster Carr.
Even today some tool manufacturers will assemble their tools with odd-ball threads like a metric 8.8 or 8.85. A non-compatible thread will sometimes go in up to 3/4 of the way then bind up and more times than not it will just get tightened home and damage the threads. In this case the original hex stock may have been for a special purpose, possibly a military spec or for a specific application so it could not be easily messed with.