Thread sizes below 1/4 confusing

moparspares said
Yeah Qld, Australia. We are all metric here but of course you can buy imperial sizes but anything even slightly offbeat and your out of luck. I called about 10 fastner places the the other day and some had never heard of the free spinning washer nut and one guy even said they dont exist. I said they do I have one in my hand. I was at a fastner place yesterday to buy some more 10 - 24 threaded rod and out he comes with it. On the tag it says 3/16 and then says same as 10 -24. Yeah my whole point bloody confusing.

Well don't let the bewildered and clueless confuse you.
You now know the American or Unified thread system.
Not to be confused with Whitworth or British Standard. yet again different thread forms and designation method.

3/16 = .1875
10 = .1900
But 3/16 is not a proper American designation.
There is a British Standard Whitworth 3/16-24

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