In this thesis CNC machine maintenance was explored as a key part of a manufacturing company. Machine maintenance has to be done in an adequate way, according to CNC machine manufacturer specifications. Through technological development, and an increased need for manufacturing development, tool machines have also advanced. In a span of almost 250 years tool machines have advanced from the first steam engines to modern numerically controlled machining centers. With this development, machine maintenance requires greater knowledge and skill. Also, to achieve quality maintenance, it is necessary to have well developed technology and track the technological process. In the last chapter of this thesis, some procedures for CNC turning machine maintenance are listed with some of the more common faults. Through these examples we can see how the machine maintenance is a demanding process in any company, but is necessary for continuing operation of tool machines.