Best Size of Thread For Threaded Tang

[Atownlokal57]

I've made approximately 800 take-down knives. Only a few were NOT 10-32. A few larger scale knives were 12-28. Whatever size diameter you choose, go with the fine thread for that size.
The yield strength for a 10-32 is about a 1/2 ton.
If forging the knife, you MUST! give as much attention to post forging thermal cycles and such to the tang as you do the blade. That tang is now a working portion of the knife.

Where can I find #10-32 tang nuts? I’ve looked everywhere

 

[Alex Topfer]

The exact thread won't matter, you can use something similar. #10-32 is close to M5, M6 would be fine. I've used M4. These will all work if the rest of the handle is well made (tight fits, appropriate washers, ect)
Pommel nuts are pretty esoteric hardware in the general scheme of things, so you may not be able to buy them. A domed nut might be an option, or a local machine shop may be willing to make some for you though that's unlikely to be cheap

 

[Stacy E. Apelt - Bladesmith]

For pommel nuts get Acorn nuts. They may be fine as-is. I put them on a bold and turn them to shapes with curves and indents.
Other things that work are lamp shade finials. They come in everything from rounds to fancy shapes.
A good way to get a steel pommel nut is make one. Tap a hole in a round piece of steel or damascus and turn it on a matching bolt. A power drill strapped to a 2X4 in a vise will work as the lathe. Use files to shape it and sand with sandpaper to the desired finish. Etch or blue as desired. Fire bluing is simple and looks good.