SKX1680 bare machine is integrally formed cast irons, with high bearing capacity and high-density ribbon structure. SKX1680 takes stress reduction as the design concept, and is processed by secondary tempering after being naturally aged for 3 months, so as to ensure whole quality stability of machine tool. The Y-axis motor is postposed and can be maintained conveniently, so as to reduce the operation distance at the front part. The stanchions adopt large-span herringbone structure so that the excellent stability of mainshaft head can be improved when moving. The counterweight hammer for mainshaft head is a hidden counterweight hammer and is fixed by a guide rod so that the machining precision is not influenced owning to the shaking of counterweight hammer. The machine tool body adopts a widened base so as to ensure the worktable moves in a fully supported way. The three-axis guideway adopts imported overloaded precision-level linear guideway. Y axis is supported by four guideways, while X axis is supported by six sliding blocks. The screw rod adopts imported R50-010 C3-grade grinding screw rod, with two ends being fixed and pre-stretched. All bearings are imported P5-grade bearings in pair. The mainshaft is BT50 precision mainshaft produced in Taiwan, with the maximum rotating speed of 6000r/min. Stainless steel protective shields are provided before and after Y axis, on the left side and right side of X axis and below Z axis. Furthermore, automatic lubricating systems are provided, and tool storage mounting surfaces are reserved. The appearance of bare machine shall be painted with required colors. The bare machine does not contain any electrical apparatuses.