Abstract:When valve cover holes are manufactured in medium batch, the traditional method is to use two sets of fixtures of drilling and boring to machine. By using this traditional method, it has the disadvantages of increasing work in design, and it also has a margin of error caused by repositioning of the fixture. To solve this problem, a set of doublepurpose fixture was designed to finish the work which was required to be finished by two sets of fixtures mentioned above. By using UGNX 70, 3D simulated assembly of the fixture was done. It is shown that this fixture can be used on both drilling machine and boring machine through replacing drilling set or boring set, no need to reload the workpiece.So the cost in designing fixture is reduced, the machining accuracy of the part is ensured and the production efficiency is improved.