For efficient and high-quality design of mechanical products, it is now possible to use virtual product models as a basis for functional simulation and verification. However it is not easy to evaluate human operational interfaces of such virtual products only by graphical interfaces. In this paper, a method is proposed to simulate human operational interfaces by use of generic haptic devices. Based on behavioural simulation of virtual product models, appropriate information for haptic interaction is generated, and machine operational interfaces are simulated by use of generic haptic devices. For evaluating the effectiveness of the proposed method, assessment of virtual mechanical switching operations has been performed.