Stiffness of a machine must be known between the tip of the cutting tool and the surface being machined in order to correlate with microfinish. Signature of the machine tool and its environs are registered on the micro-machined surface. Imperfections are triggered by disturbances which may originate off the machine, from the machine, or by reaction between the tool and the workpiece. The machine transfer function is a complex mechanical system with many input points and resonance frequencies to be contended with. This paper deals with recognizable surface imperfections which are related back to mechanical parameters in and between the machine elements. To be complete, one must include spindles, slides, supports, vibration isolators, tool holders, tools, fixtures, and the workpiece itself. Their relation to sources of disturbance is discussed and examples are given of surface measurements made which identify the relation between machine stiffness and microfinish signatures.