Jet bench grndr spndl nut specs?

I recently came across a oneway wheel balancing system for grinders with a 1/2" spindle. Unfortunately, the spindle on my old Jet 6" grinder is a bit too short (1/8" or so).
I was thinking oneway I could make things work would be to use thinner nuts on the ends of the spindle.
Another way would be to machine the ends of the flange pieces down by about 0.160", which will still allow a 1" wide wheel to be used.
What are the specs on those nuts?
I know one is RH- and one is LH-threaded, and I think both are 1/2" diameter. I measured 12 threads per inch with my (std) gauge, but the common course thread 1/2" nuts are 13 tpi.
The closest metric size would be M12x2.0, but again the thread pitch is funny. Most M12 are 1.25, 1.5, or 1.75mm per thread. Maybe it's 1.75 ?
Any one know this spec for sure and even better where I might find a high grade, thinner, LH nut like this?
I could also machine the existing nuts thinner, but I'd rather use a higher grade, thinner one.
Thanks for any suggestions.
Jeff Dantzler

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