A major problem with the wide variety of manufacturing engineering software applications which are available is that they are not designed to work together. Research is being performed at National Institute of Standards and Technology (NIST) to identify the integration standards and validation issues that must be addressed to implement plug-compatible software environments. One of these efforts is the Manufacturing Engineering Tool Kit (METK), an integrated toolkit providing applications for performing product design, product data and workflow management, operations planning, and engineering data validation using simulation. In this paper, we present an interface for integrating the operations planning application and numerical control programming simulation application. Two categories of manufacturing data validation strategies -object validation and operation validation - are also presented. Finally, the benefits of a generic interface and manufacturing engineering data validation are discussed.