What tool is used to true a grinding wheel?

The tool used to true a grinding wheel is the dressing tool. This specialized tool is essential for maintaining the wheel's shape and performance. Truing refers to the process of realigning and reshaping the grinding wheel to ensure it operates correctly and efficiently. A properly dressed grinding wheel will have a consistent surface and will remove material more effectively.

Dressing tools are specifically designed to remove material from the surface of the grinding wheel, allowing it to regain its sharpness and effectiveness. They typically consist of abrasives or diamond grit, which can effectively wear away any irregularities or buildup on the wheel.

In contrast, tools like cutting tools, mill files, and sandpaper serve different functions in machining and finishing processes. Cutting tools are generally used for cutting materials, while mill files are meant for smoothing surfaces and edges. Sandpaper is primarily employed for hand sanding and finishing tasks but is not suitable for the specific job of truing a grinding wheel. This distinction makes the dressing tool the correct choice for the question at hand.