I had a class project that was going to need a machinist jack, and looked around and found a couple of designs that had this telescoping design. I may have been a little excessive with the “precision” part. The running joke in the shop whenever I need to take the top-most part out and it takes just a little longer than what an awkward silence can handle is: “Some wise guy decided to make a 1/2-40 thread”. This was really good practice in single-point threading custom thread sizes to tolerance. This part features a 3 start 7/8-12; so 3 threads running at 7/8-4 and a 1/2-40 thread.