Very nice, Eric!
I’ll second what Nathan said. I either press them on or use some hardened steel spring-like metal screws just like the store-bought screw-on file handles. Don’t remember where I picked them up, but I like the metal inserts better than the
plastic inserts I used to use, and you can unscrew the handle and reuse it if you happen to wear out the file.
The other thing I have is a piece of tool steel a buddy back in MN cut to match the two sizes of file tangs I had. I can heat that up over and over if I really want to burn handles on. He made one for the two sizes of Mora knife blanks I use most, too. But I don’t think I’ve burned a handle in since moving to NM.