With the usual clamping method, it is difficult or even impossible to clamp the entire surface of the thin plate member at one time. The pressing of the thin plate member on the flat plate cannot always be completely flattened, and the plane milled by the milling machine has flatness error. For this problem, a thin plate clamping method can be used. The arc body is clamped by two splints, and the splint is connected to the two pressure plates through the pin shaft, and the screw passing through the pressure plate is screwed on the circular arc body. When milling, place the thin plate on the upper end arc of the circular arc body, press it down to attach it to the circular arc body, and clamp the upper surface with the same arc diameter flying knife after clamping on both sides with the pressure plate. Come over and mill the other side. Because the workpiece is bent downward, it can be closely attached to the arc body, the flatness error is small, the machining precision is high, and the entire plane can be milled and clamped at one time without a tool mark. Use a three-jaw self-centering chuck as a milling fixture. When vertical milling is required at the ends of shafts, sleeves, discs, and tubular parts, a three-jaw self-centering chuck can be used as a milling fixture to mill the above parts. When it is not necessary to install the positioning shaft in the center hole of the chuck, the three-jaw self-centering chuck can be directly pressed onto the table of the milling machine as a milling fixture. When it is necessary to install the positioning shaft in the center hole of the chuck, the height dimension of the positioning shaft is calculated according to the length dimension of the workpiece, and the positioning shaft is driven out according to the size, and the three-claw self-centering chuck is directly placed after the vehicle is in good condition. In the center hole, sometimes to prevent the positioning shaft from vibrating during milling, a T -bolt can be used to fix the positioning shaft to the T -shaped groove on the table.