Machine tools with parallel kinematic structures (PKM) are known as 3- or 5- axis machines, which are typically used in drilling and milling work, but PKMs can also be employed in laser machining or high pressure jet cutting. This type of machining necessitates high precision requirements similar to that attained with conventional machine tools. Particular attention must be paid to the mastery of spatial measuring techniques in order to ascertain the exact tool position within the working area. Furthermore, the static, dynamic and thermal behavior of the machines are a crucial judgment criterion for the vast number of structural configuration possibilities provided by PKMs. Experimental and analytical investigations widen the realm of knowledge in PKM optimization, illustrated in this paper with examples of realized machine structures.