Which of the following is a precise method to verify shaft alignment?

• A. Visual alignment by sight
• B. Dial indicators or laser alignment
• C. Estimating alignment by weight balance
• D. Using a ruler across shafts

Answer: (B)

Precise shaft alignment comes from measuring how the two shaft centerlines relate to each other with a tool that gives quantitative data. The best way to verify this accurately is using dial indicators or a laser alignment system. Dial indicators measure small differences in position at the coupling plane and, when used in multiple planes (often 90 degrees apart), reveal both parallel (offset) and angular misalignment. This lets you adjust feet or shims until the readings are within manufacturer specs. A laser alignment tool does the same job by projecting a laser along the shaft centerlines and using sensors to detect any deviation, usually providing a fast, highly repeatable, and highly precise readout.

Rough methods like visual sighting or using a ruler or estimating by weight balance aren’t precise enough for reliable alignment; human sight can’t detect very small misalignments, and crude tools won’t capture angular errors or give repeatable measurements. Misalignment leads to vibrations, excessive bearing and seal wear, and wasted energy, so using a precise measurement method ensures the shafts run true and the coupling is loaded evenly.