It is difficult and costly to cut good parts using bad machine tools. If the machines worked right in the first place, that time could be spent more profitably, producing parts. The process is a valuable approach to ensuring quality in the metalworking trades. Statistical process control may reveal that something is wrong with the process, but it often fails to indicate precisely what. Machine tool evaluation can identify the problem and suggest means to solve it.
Machine tools can go wrong in dozens of ways.
Every axis of motion has a number of potential inaccuracies of position and orientation. Each linear axis may exhibit errors of pitch, yaw and roll. Each may have errors of straightness, and of squareness relative to the other two axes. Each is subject to errors of linear positioning. The machine's spindle is also subject to axial and radial errors.