@zov the only direct contact detection that it wouldn’t work for is electrical since the nozzle tip is a ruby. Piezo based and strain-gauge (smart effector) will work. I think starting with hardened steel is a great choice. 🙂
Thanks, it's an idea sure. In the end I got a local engineering firm who are literally 200 yards from me to measure the rods (with high grade bearings at each end) on their bewildering array of large calipers. They were not significantly different from one another:
So I doubt I'd see the difference in the lines if I drew them on the bench, we're talking about a variance of 40 microns. The same with the balls, whilst there was a difference in diameters it was very small. Matching up the rods and balls to achieve 3 pairs of almost exactly equal length yielded no change in calibration or print quality in my otherwise all-metal and very precise kossel XL, compared to the situation I had before where they were all basically random.
But if Haydn has commissioned a new batch of balls that are much more precise, then this matches the rods which are made to very tight tolerances, and marketed as such.