TH850 bare machine is integrally formed by precision casting through resin sand type high-strength cast irons, with reasonable ribbon structure, good rigidity, totally aged treatment and strong stability. The Y-axis motor is postposed and can be maintained conveniently. The stanchions adopt herringbone structure so that the excellent stability of mainshaft head can be improved when moving. The counterweight hammer for mainshaft head is fixed by a guide rod so that the machining precision is not influenced owning to the shaking of counterweight hammer. The three-axis guideway adopts imported overloaded precision-level linear guideway, with larger size than that produced by general factories. The screw rod adopts imported R40-010 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 BT40 precision mainshaft produced in Taiwan, with the maximum rotating speed of 8000r/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.