When the workpiece fixs its position, we must limit the precision machining of freedom which impact the SKF bearings; if it does not affect the SKF bearings' precision,we can limit the degree of freedom or not, it bases on the specific case. Determined the limited workpiece of freedom in accordance with requirements of the workpiece is positioned the first problem

As the required size of the groove depth is A2, therefore we should seek to restrict the freedom of movement of the z direction; Because of the demands is that the c-plane should parallel to the bottom surface, so the x-axis rotational degrees of freedom around the X and y-axis rotation around y to restrict freedom; as to ensure the long slot of A1,so we should restrict themoving freedom of X in the x direction;  as the guiding groove in the center of plate, coincide with the long hole, therefore,w should limit the freedom of movement in the y direction and restrict freedom of turning degrees of z axis, Thus, when we process the guide groove, six degrees of freedom should be restricted.This six degrees of freedom are restricted is called completely positioning.

If we rud the plane on the surface grinder, it should assure the thickness of board, and processing should be parallel to the surface and bottom, then, according to the processing requirements of SKF bearings, we can only limit the Z, X, Y three degrees of freedom . According to processing requirements of this part of the actual limit is less than six degrees of freedom positioning method is called incomplete positioning. If the workpiece is in a machining process, parts processing requirements should be limited according to the degrees of freedom is not restricted due to the positioning method is called not enough positioning. not enough positioning is not allowed appear in processing