I believe there is a mistake in that selection in that I cannot find any reference to a "UNC" (Unified National Coarse standardized thread) measuring any fraction less than 1/4" or 0.250" diameter. I believe it is some foreign (meaning some company that is not following the standards) invention that does not really exist.
From Wikipedia:
"Designation
The standard designation for a UTS thread is a number indicating the nominal (major) diameter of the thread, followed by the pitch measured in threads per inch. For
diameters smaller than 1⁄4 inch, the diameter is indicated by an integer number defined in the standard; for all other diameters, the inch figure is given.
This number pair is optionally followed by the letters UNC, UNF or UNEF (Unified National) if the diameter-pitch combination is from the coarse, fine, or extra fine series, and may also be followed by a tolerance class.
Example: #6-32 UNC 2B (major diameter: 0.1380 inch, pitch: 32 tpi)"
<end quote>
This has also been my experience over years of actually working in the fastener industry.
Put more simply, I thinks whats ya' gots dere is 'some guy's' imaginary version of a "standard" thread that is neither standard or even in use anywhere.
![Shocked :o](http://zggtr.org/Smileys/default/shocked.gif)
Brown and Sharpe (machine tool and measuring instrument Co. located in RI and an industry leader) used to make up their own threads, such as 17 1/2 TPI, but they were not standardized threads, rather a deviation from <any> standard to force a machine owner to purchase ONLY B&S hardware going forward. As you spec. sheet calls out "UNC", this would indicate a true, unified, standardized thread but I can not find any reference to any such thread. Such my thought that it is either some type of linguistic translation mistake, or a thread made up on the fly from someone's fertile imagination. At any rate, I betcha' you have several life- time supplies of rivets for screws you will never actually see and / or find. :-)
Brian
No, the set I purchased had those (#8) as well, and using a thread checker, the 5/32-32 would go loosely onto a 6-32 and only just start on a 8-32 but not go all the way on it.
I also found it strange that the rivet size for the 5/32"-32 was larger than for the 8-32 even thought the major diameter would be smaller. ![Huh? ???](http://zggtr.org/Smileys/default/huh.gif)
This one--> [url=https://www.amazon.com/gp/product/B07HL45TFL/ref=ppx_yo_dt_b_asin_title_o01_s01?ie=UTF8&psc=1]https://www.amazon.com/gp/product/B07HL45TFL/ref=ppx_yo_dt_b_asin_title_o01_s01?ie=UTF8&psc=1[/url]
I'm beginning to think that the 5/32-32 is a Whitworth cap screw size possibly out dated, as I'm told it's listed in a 1957 version of Machinery's Handbook, but I couldn't find it in my '66 edition. Maybe if I reach down into the cushions of my sofa I'll find an earlier edition?
![](https://images-na.ssl-images-amazon.com/images/I/71OaLUiuC0L._SL1100_.jpg)