Desmond Stephan vises have come up before and almost always with a request for replacement bronze half-nuts. I’d picked up a Desmond some time ago with the intention of making it my main vise and upon cleaning was having seconds thoughts about the lifespan of the nut.
I was recently cleaning up a Morgan 100 “Rapid Action” and noticed the half nut looked remarkably like my memory of the Desmond. I was actually cleaning the vise to pass on to someone else as it was smaller that my others and was missing the option for a dog. So I dug out the Desmond (which in a mental lapse I’d applied some white lube to) and to my surprise found the half nuts to be the same. The final test was to swap the much fresher Morgan half-nut into the Desmond. The only fiddling I had to was make sure the half-nut was fully seated and I had to use the spring & pin from the Desmond. The depth of hole for the spring tensioner was different and the softer spring was necessary for smooth action.
I did notice that the thread pitch was a little different between the screws of both vises. I couldn’t take a highly accurate measurements because I don’t have any acme thread gauges. The Morgan screw was ~1.24″ OD and 4 TPI the Desmond screw was ~1.25″ OD and 4.1 or 4.2 TPI, just slightly more than the Morgan. This got me concerned about the TPI of the half-nuts. Given the wear on the Desmond nut it’s a little hard to tell but they both looked the same to my measurement. When I gave some thought to the wear on the Desmond I realized that it was consistent with a slight mismatch in the TPI of the screw and nut.
So, the Morgan 100 and Desmond half-nuts are interchangeable and the high wear rate of the Desmonds might be attributed to some sloppy machining.
The better news is that this part is still available from the owners of Morgan. It’s part 23 “Old Style” nut, item #1141023. I was quoted from a price list $27. Not cheap, but it’ll put a $10 vise back into service. They also have other parts. Contact: firstname.lastname@example.org