What is a disadvantage of cross-dial alignment?

• A. It is quick to set up
• B. Accuracy decreases if coupling spans are less than 4 inches
• C. Both shafts must not rotate
• D. It offers superior accuracy on all spans

Answer: (B)

The identified disadvantage of cross-dial alignment is that accuracy decreases if coupling spans are less than 4 inches. This is a significant consideration in alignment practices because shorter spans create difficulties in accurately measuring slight misalignments. When the distances between the coupling points of the shafts are minimal, the resolution of the dial indicators may not be sufficient to detect small errors in alignment.

In alignment tasks, especially with cross-dial methods, it is crucial to ensure that there is an adequate distance between the indicators to obtain reliable and repeatable measurements. Short spans lead to less effective readings due to potential fluctuations and increased relative movement, impacting the overall accuracy of the alignment process. Thus, understanding the limitations of cross-dial alignment concerning span lengths is essential for achieving optimal results in machinery alignment.