I have an old beam compass. This was my first "beam compass", and it came from my wife's uncle (no one in his family wanted it, and probably didn't know what it was), so I inherited it. It was missing the beam, so I ordered a section of 3/16" hex bar, sliced it where the bar was bent, and ended up with three sections.
As this sat in my drafting kit, I wanted to be able to use all three sections. With my current health conditions, I've been banned from using cutting tools for a few months (and will be for a few months more), so I had to sneak this one in.
A quick run to the lathe with some 3/8" stainless bar stock, and I drilled a 3/16" hole through the middle.
The hex bar stock is 0.214" across the peaks, and that was right up the alley of a #12-24 thread (0.216" outside or major diameter). So, I tapped the "tube" half way to #12-24.
I then did an interrupted thread cut the hex bar stock on lathe, ran a thread cutting die to finish it, and turned the other end of the hex bar stock down to 3/16" to fit those tubes.
The beam compass extension tubes needed a set screw. I opted to make it like the other screws the compass had - a #5-44 thread to match. The only problem was that I did not have horizontal/vertical knurling wheels, and I've spent too much on tooling for this already to make it anywhere near worth while. But, I had the bar left over from the tubes, so I made some thumb screws with some diamond knurls.
The screws fit, and locked everything up as I'd expect.
This is done! (Except for maybe one part to hold lead instead of a hard point like a divider - we'll see.)
