Shaft alignment — rim & face
Enter your rim and face dial readings and three distances to get the shim change at each foot, graded against field tolerance.
Convention: dials mounted from the stationary machine reading on the movable hub, zeroed at 12 o'clock, read at 6 o'clock. Positive = plunger pressed in. Correct the rim reading for bar sag before entering it.
Result
Shim both feet, re-take the readings, and expect a second pass — alignment converges by iteration, not by one perfect move.
How is this calculated?
Using the tool
Two dial readings describe the whole misalignment: the rim reading gives the offset at the coupling, the face reading over the face diameter gives the angle. Enter both with your three distances and get the shim change at each foot of the movable machine — plus how the as-found condition grades against field tolerance for your speed.
The geometry
A misaligned shaft has exactly two problems at the coupling — it sits offset from the stationary axis, and it points at an angleto it. Rim & face measures one each: the rim dial rides the hub's outside, so its 6-o'clock reading is twicethe offset (the hub is displaced once going down and the dial sees both sides of the circle); the face dial rides the hub's face, so its reading spread across the face diameter is the angle in mils per inch. From there every correction is the same line extended: shim change at a foot = angle × distance from the dial − offset. The front foot needs less, the rear foot needs more — that's the angle doing its work over distance.
New to the math? Learn the concept: Industrial mechanic fundamentals