I've seen a number of cases here where inductive/proximity switches are mounted to detect when an axis moves tangentially to the sensing face. In all the manufactures data that I've seen the advice is to mount the sensor such that the detected face is presented axially to the sensor. I'm guessing one issue with mounting the sensor tangentially is that it's clearly immune to damage due to crashing the axis into the sensor, but are there any negatives? (repeatability would be the one that springs to mind)