Which of the following is a proper maintenance step for a micrometer?

Regularly wiping the spindle and measuring faces with a dry cloth is essential for maintaining a micrometer. This practice helps prevent the accumulation of dirt, dust, or oil, which can compromise measurement accuracy over time. Keeping the measuring surfaces clean ensures that measurements remain precise and reliable, as any foreign substances can lead to erroneous readings. Regular maintenance like this is a vital part of ensuring the longevity and functionality of the instrument.

Using water to clean a micrometer is not advisable, as moisture can lead to rust or corrosion on the metal components. Additionally, maintaining contact between the spindle and anvil can cause wear and potential damage, affecting the instrument's precision. Storing the micrometer in a humid environment is also detrimental, as humidity can lead to rusting and negatively impact the mechanical parts and electronic components if applicable.