Arrggg!!
The largest metal wing nuts are too small, and a regular nut threads
are too fine for the wooden threaded shaft of the frame. A 3/4" nut
will fit, but it won't screw down the threads because they don't match.

Unless I can find a hardware store or source that carries obscure
sizes;
I bought my frame set over 20 years ago- it's all oak-
no metal parts at all.
Alas and Alack! sigh 8(
MM