Have you used the Klein jig or similar to thread wooden pen caps? What would be involved? How many threads per inch would be optimum for the sizes involved?
I have used my Klein jig to cut threads on box lids but couldn't imagine using it for something as small as a pen cap. The cutter I use is about 3/4" in diameter and you would need something small enough to go inside the cap. I think taps are the way to go.