How to treat the tolerance of paper outline

In the figure, a generally represents datum, and the general surface contour can be marked without datum. The tolerance zone is an area defined by two enveloping surfaces of a series of spheres, the diameter of which is tolerance value 3, and its center is located on the theoretically correct geometric shape of the measuring element determined by the datum plane.

The tolerance of contour is similar to that of position. The relevant dimensions are framed to indicate the theoretical correct position, and the tolerance is the distance between the "two faces" symmetrical with the theoretical outline.

Measure the size of the surface relative to the reference with reference to A, B and C (maximum solid time) respectively. When the measured size is within the marked theoretical size 1, it is qualified. If the C datum is not in the maximum solid state, the contour tolerance of the datum can be "relaxed".

Extended data:

The method of marking the tolerance of line profile correctly;

1. The marking of line profile tolerance without datum requirement requires it to have an ideal curve shape, and there is no position datum requirement when it is used. When marking, the theoretical correct size should be applied first, and then the frame guide line arrow should be pointed to the measured contour line along the normal direction of the measured element contour line.

2. In order to mark the tolerance of line profile with reference requirements, the tolerance requirements of outgoing line profile should be given on the drawings. The tolerance zone is an area defined by two enveloping surfaces of a series of spheres, the diameter of which is the tolerance value t, and its center is located on the theoretically correct geometric shape of the measuring element determined by the datum plane.