I had one year of shop class prior to the engineering college, and I was actually quite skilled at using a lathe at that time. However that was 24 years ago.
The two most difficult things as far as I remember was turning correct fits for bearings, and to cut threads on the lathe. Not the type where you use a tap or a die, but grinding the tool bit and adjusting it all and then lead the lead screw take care of the pitch.
Searching for an appropriate challenge, I ended up reading about the Stanley # 20 compass planes.
According to Patrick Leach's excellent pages on Stanley planes , the # 20 often has the original knurled locking screw replaced. So making a new one of those might be helpful to someone out there sitting with a recently acquired #20 missing that screw.
However excellent Leach's page is he doesn't reveal the thread of this screw, but I managed to find that information on a British tool forum.
The screw was apparently of the much under appreciated UNS standard, namely a UNS #10-28.
This just kept getting better and better!
A rare screw with a sort of obsolete and no longer used standard.
I googled the Standard and found the necessary information about the thread, so I could proceed to the workshop.
We have a very limited supply of tools for the lathe out here, and off course the most important thing for thread cutting was missing: A thread cutting tool.
After scouring the shop I found some old parts from a diesel injection valve, and those parts are made out of hardened steel. So I ground one of them into a 60 degree tip so I had something to use.
A piece of brass was turned to the desired dimensions, and then it was literally time to change gears.
Most simpler types of lathes that have a thread cutting capability will need to have the gears changed in order to switch from metric to module to imperial threads etc.
There are some small tables on the face of the lathe that will tell you how the correct configuration is, and once you have got that right, you just need to correctly position two handles and two knobs - and you are ready to go.
On the first attempt I managed to mess up the thread. But on the second attempt it came out all right. I think it could have been a bit more crisp, but without a proper thread cutting tool and an thread cutting tool position gauge, I just had to sort of eyeball it.
After the threading, I inverted the cutting tool, and used one of the gears as a dividing head, so I could make some knurling lookalike.
Due to my goodhearted nature, I have decided to offer this screw for free - to the first Alicante based American woodworking blogger that comments on this blog.
Gear setup for metric (42:120:42)
Gear setup for imperial 28 TPI, (32:120/127:48)
Stanley #20 locking screw.