Which tool is commonly used to check shaft alignment?

• A. Calipers
• B. Straightedge
• C. Dial indicators
• D. Laser alignment tools

Answer: (C)

When checking shaft alignment, you need a tool that reveals tiny linear differences between the two shafts in their operating position. A dial indicator is ideal for this because it directly converts small vertical or horizontal deflections into movement on a readable dial. By placing the indicator against a reference surface on one shaft (or a coupling flange) and taking measurements in multiple positions (top and bottom, or different angles), you can uncover both parallel offset and angular misalignment. Those readings let you determine how much to adjust the machine feet, the coupling, or shims to bring the shafts into alignment within tolerance. Dial indicators are portable, relatively inexpensive, and provide high-resolution, repeatable results, which is why they’re commonly used for shaft alignment checks.

Calipers measure distances but don’t capture the relative misalignment between rotating shafts. A straightedge can help with rough guidance but can’t quantify small angular or offset errors. Laser tools are precise and fast and are widely used in many setups, but dial indicators remain the standard go-to in many shops for a hands-on, cost-effective alignment check.