I have been looking for a good solution for mounting a Hi-lift auto jack on my Jeep. Since the rear frame is made of steel tube, I decided to make a pair of tubing clamps, similar to what I have seen commercially. The main difference is that these cost me less than $5 for fasteners, vs. $60 for a store-bought pair.
The first step was to cut a 1.75" slice from a length of 3" diameter aluminum rod. I then faced, turned, and bored the piece on the lathe, then parted off into two .75" thick rings. Since the tubing I will be placing these on is 1.75" diameter, I bored the holes .05" oversize.
The rest of the operations were milling. The finished result looks like this:
While the work is conceptually pretty simple, making a pair of these took the best part of 5 hours. Mounted on the Jeep's rear frame, here's one of the clamps:
The central mouting bolt is 1/2-13, while the two clamping bolts are 1/4-20.