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Shaft Alignment Calculator

Reverse Indicator Method - Shim & Move Corrections

Field calculator for dial indicator and laser alignment — Enter machine dimensions and readings to calculate corrections

Download Our Field Alignment Sheet
1 Machine Dimensions
in
S indicator to M indicator
in
Movable indicator to front feet center
in
Distance between foot bolt centers
mils
Bracket sag (negative value)

📏 How to Measure Dimensions

  • A: Center of stationary indicator to center of movable indicator
  • B: Center of movable indicator to centerline of front feet bolts
  • C: Front feet bolt centerline to back feet bolt centerline
  • Sag: Mount indicators on a rigid bar, rotate 180°, read deflection
2 Operating Speed & Tolerances
RPM
Offset Tolerance
2.0
mils
Angular Tolerance
0.3
mils/in
Based on ANSI/ASA S2.75-2017 Acceptable Grade
3 Thermal Growth Compensation (Optional)
Stationary Machine (Pump/Driven)
in
°F
Movable Machine (Motor/Driver)
in
°F
Thermal Growth Offset Target
+3.1
Set motor 3.1 mils LOW when cold
4 Reverse Indicator Readings (TIR)

Enter Total Indicator Reading (TIR). Zero on TOP, read at BOTTOM for vertical. Zero on LEFT (9:00), read RIGHT (3:00) for horizontal.

Vertical Plane (Shim Corrections)
S - Stationary Side Reading
Indicator on movable, reading stationary shaft
mils
M - Movable Side Reading
Indicator on stationary, reading movable shaft
mils
Horizontal Plane (Move Corrections)
S - Stationary Side Reading
Zero LEFT, read RIGHT
mils
M - Movable Side Reading
Zero LEFT, read RIGHT
mils

⚠️ Sign Convention

Vertical: Positive (+) = indicator compressed at bottom = motor shaft HIGH
Horizontal: Positive (+) = indicator compressed at right = motor to RIGHT (viewing from motor to pump)

5 Calculated Corrections
Vert. Offset
-2.0
mils
Vert. Angular
0.33
mils/in
Horiz. Offset
+1.0
mils
Horiz. Angular
0.17
mils/in
Vertical Corrections (Shims)
Front Feet
+4.7
mils
ADD SHIMS
Back Feet
+9.3
mils
ADD SHIMS
Horizontal Corrections (Moves)
Front Feet
+5.3
mils
MOVE RIGHT
Back Feet
-2.0
mils
MOVE LEFT

⚠️ ACCEPTABLE - Within Tolerance

Alignment meets acceptable standards for 1800 RPM operation.

Graphical Shaft Alignment Plot
Stationary Shaft Centerline
Movable Shaft Centerline (As Found)
Target Alignment
Reverse Indicator Formulas

Shim Correction Formulas

S = Stationary TIR ÷ 2
M = Movable TIR ÷ 2
Front Feet = ((M - S) ÷ A × B) + M
Back Feet = ((M - S) ÷ A × (B + C)) + M

Positive result = feet are HIGH → Remove shims
Negative result = feet are LOW → Add shims

Misalignment Calculations

Offset = (S + M) ÷ 2
Angularity = (M - S) ÷ A

Thermal Growth

Growth = α × L × ΔT

α = Coefficient of thermal expansion
L = Centerline height from base
ΔT = Temperature change (°F or °C)

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