July 30, 2018
Setting Tolerances in Fixturlaser Shaft Alignment Tools
By Steve Gordon
Fixturlaser Shaft Alignment Tools come pre-programmed with generally accepted industry tolerances for electric motor driven machinery. These tolerances are based on the motor RPM and will give you an “endpoint” in the alignment process (based on the measured offset and angular misalignment at the center point of the coupling in both the vertical and horizontal planes).
These general tolerances work well for most industrial applications, motors driving pumps, fans, etc. In the USA, Angular tolerances are set in Mils/inch. Offset tolerances are set in Mils (1.0 mil = 0.001”).
But what if there are special applications where the OEM has specified a different tolerance such as for compressors or wind turbine generators? No problem! Fixturlaser shaft alignment tools allow you to set a customized tolerance for your application. From the Display Unit:
- Select the Horizontal Shaft Alignment Program
- Open the tolerance table
- Name the tolerance and input the angular and offset values desired.
This procedure is referenced in your Fixturlaser User Manual listed under “Tolerance Table” or in the section “Shaft Alignment Horizontal Machines”.
If your tolerance is specified in dial indicator values, typically in total indicator readings (TIR), it is simple to convert these to Mils and Mils/inch.
Offset conversion = Rim indicator TIR value divide by 2, or ½ the TIR.
Angular conversion = Face indicator TIR value divide by the diameter of the coupling.
Example: OEM tolerance is 0.005” or 5.0 mils (TIR) for both angular and offset misalignment. The coupling diameter is 10”.
Offset: 5.0 mils ÷ 2 = 2.5 mils (0.0025”)
Angular: 5.0 mils ÷ 10” = 0.5 mils (0.0005”)/1”
You can also use our free Laser-Dials App or call VibrAlign for help @ 800-394-3279.