OVERVIEW

A dial indicator, being the precision instrument it is, can more easily give a false reading than accurate. This statement could easily be mislabeled a paradox; but it is not. A flawed reading is almost never the fault of the instrument, but human error.

While there is practically a myriad of ways to position indicators incorrectly, there are but few settings that would be considered correct for each unique application, When indicators are mounted to get a rim reading on a coupling, the indicator stem should be set to aim straight through the center of the shaft, at a perpendicular to the axis of the shaft. This centershot at a perpendicular doesn t have to be absolutely perfect, but it should be close enough that a closer than casual visual inspection can find no flaw. This is close enough for practical purposes.

As a novice millwright helper/apprentice in the mid-1950 s I used to marvel at the skill with which some of those millwrights I worked with could set those little stop watches at all kinds of crazy angles to get readings while doing alignment work. Little did I realize that (on the subject of shaft alignment with dial indicators) they knew but little more than I at the time. Sure, they would finally get the alignment done, but it was very slow. They knew that on a rim indicator reading to divide by 2, but when things went wrong, rust or faulty shims or me, or just anything but...