Not a heating problem, more like a machinist problem

So I am trying to fix the depth adjustment on my Skillsaw because I can't adjust it. I had to pretty much completely disassemble the whole saw to get access to the depth adjustment knob.

After I cut the plastic knob off I am left with a threaded stud with a nut on it. Easy fix. All I need is a plastic insert nut or two nuts to lock together and I would be all set. No problem, right??

So the existing nut threads on and off the stud easily just as it should. No problem.

It looks like a 1/4-20 so I tried a 1/4-20 nut. No Good, won't thread on

It looks like a course thread but I tried a 1/4-28 fine thread nut. No Good

I tried a #12 nut. No good too small

The OD of the threads is .243-.244 with my micrometer

I went to the hardware store and got a 6mm metric nut..........too small

I also found a 7mm metric nut (which isn't even listed on most metric charts).......too big

I tried to run a 1/4-20 tap into the nut as a second check.....no good

1/4-28 tap .......no good

Again the existing nut threads on and off the stud easily... fits perfect!

I used to have some thread pitch gages gotta look for them

Skill"s website doesn't list the part separately and most parts for this saw are obsolete

Can't figure out what this is

I will probably just cut the stud off if I can and change it.

It's just such a simple thing...maybe that's why it's driving me nuts.

What else could it be??