Which tool do you use for determining the thickness of objects, the distance between surfaces, and the depth of openings in mechanical parts?

The correct choice is calipers because they are specifically designed to measure the thickness of objects, the distance between surfaces, and the depth of openings in mechanical parts with precision. Calipers can provide measurements in both internal and external dimensions as well as depths, thanks to their two sets of jaws and a depth rod. This multifunctionality makes them ideal for tasks that require fine accuracy in mechanical engineering, manufacturing, and assembly processes.

While a depth gauge is also focused on measuring the depth of openings, it does not offer the versatility of measuring thickness or the distance between surfaces as effectively as calipers. A ruler is a basic measuring tool, suited for longer, straight measurements but lacks precision for intricate parts. Similarly, a tape measure is primarily used for measuring larger distances and is not intended for fine measurements where high accuracy is required, making calipers the superior choice in this context.