George Wilson posted how to make these in the Neanderthal forum a while back. I finally had an application for some brass knobs so I made a knurl holder, a few knurls and some knobs based on his description. The attached pics demonstrate the process.
Not pictured here, but I first made some plunge tools for the lathe so I could get the radius of the knurls and the brass knobs to match the 10x32 tap diameter. I used a 3/16 end mill to cut the right radius into a O1 blank, heat treated it and then used that as a tool bit to back cut a male form into another O1 blank, which I also heat treated. I then had matched tool bits (male and female) that I used on the lathe to cut the knurl and the brass knobs to matched 3/32" radii.
I then made the knurl holder for the lathe and the O1 knurls. I hobbed the knurls with a 10x32 tap in the lathe. This worked great! A nice accurate way to get a fine pitch knurl. I then heat treated and tempered the knurls with my A/O torch.
I set my lathe tooling up in a square turret (made this 30 years ago). I got a little production run going and could knock out a knob every 13 minutes.
A fun little project.