RAB,, thats a good idea to make your own, not too hard,,,, but,,,, when ordering the steel u would have to get it with the proper strength,, not too weak- would rip the threads out as u tried to tighten the nut down. Not too hard- seen hardened bolts shatter/ shear from vibration, think the bolts were in the SAE grade 10/12 range.
Still a great and cheaper idea than buying new nuts all the time.
Derek