Hello Jim,
I am no expert. Neither DW nor I had camped for over 30
years so in 2008 we both went crazy and purchased our first 5<sup>th</sup>
Wheel. I figure it was something that we ingested in the 1970’s. LOL
The suspension bolts in question already have the proper nut
and lock washers in place. I insured that the existing nuts were torqued down properly.
I wanted to add one jam nut on top of the existing nut to insure that the nut can
never back up on the threads. Here is a link from Portland on jam nuts.
http://www.portlandbolt.com/products..._jam_nuts.html I
was not concerned about the hardness of the jam nut. Its only job in life is to
lock the working nut in place on the bolt threads. I am sure that there is ASTM
Specification to deal with this subject. I grew up on the farm where when you
double nut something the nut just was not going to loosen. WARNING: The bolt
may stretch. Jam nuting does not mean that you should never check the tightness
ever again.
9/16-18 must be on odd size in this area of the planet.
I ended up at Menards Lumber where they had 3 jam nuts, 10
finished nuts and a few standard nuts and plenty of stainless steel nuts at
$3.20 each all were 9/16-18. There is 1.25� of exposed thread above the
existing nut that is plenty of room for a nut of any hardness being employed as
a jam nut.
If I had to do it all over again I would place an order with
http://www.mcmaster.com/#hex-jam-nuts/=gyorbq They stock jam nuts in several harnesses.
I sure hope this helps. Good luck.
Kamper Dave