The quill shaft bearings went out on my Enck bench top mill last spring and somehow, I have forever lost 1 of the shaft nuts and the remaining one has some damage, so I had been trying to locate new one for quite some time now and hadn't had any luck finding a 1.173" 20TPI left hand thread.
I can find 18TPI in right hand. But nothing that would screw onto my mill shaft. So I decided to just make my own for these I found a cylinder of mystery stainless Hacked a lump off of it turned it down bored it and threaded it then cut the spanner groves around the outside
It's not perfect but once it is down inside the quill, I'm the only one who will remember it