What is a straightedge used for in machine alignment?

• A. To measure the temperature of machine parts
• B. To check the flatness of machine bases and surfaces
• C. To align rotating shafts at high speeds
• D. To monitor electrical current through machine components

Answer: (B)

A straightedge is primarily used to check the flatness of machine bases and surfaces, which is critical in machine alignment. Flat surfaces are essential for ensuring that machines operate correctly and maintain their intended tolerances. When aligning machines, having a level, flat base allows for accurate alignment of components, reducing wear and tear and improving performance.

The flatness provided by a straightedge can help identify any deviations or irregularities in the machine's base or mounting surface. This ensures that the equipment is installed on a solid foundation, which is necessary for successful alignment of rotating parts, such as shafts and couplings. Proper flatness prevents issues such as vibration, misalignment, and premature failure of machine components.

While measuring temperature, aligning high-speed shafts, or monitoring electrical current might be relevant in a maintenance context, these tasks do not involve the primary purpose of a straightedge in the alignment process.