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Undercut dimensioning

Source: Browse:42 The release date:2021.09.01 [ Large medium small ]

The undercut can be written in the form of "groove width×diameter" or "groove width×groove depth". Under what circumstances is "groove width×diameter" used? Under what circumstances use the "groove width × groove depth" standard?

 The diameter 9.2 in the figure is the diameter of the part shown by the green line, and 0.4 is the height shown by the red line?




1. Under the premise that there is no requirement for "dimension accuracy", two types of labels (groove width×diameter or groove width×depth) can be used for the undercut, and the two can be converted. The accuracy of the free toleranceis no problem, so there is no need to consider the benchmark problem. ,

2. 1.6×0.4 undercut groove; 0.4 is the height shown by the red line, and the operator will not measure down based on the great circle. (The undercut is cut by a small round shaft)

3. The undercut has a standard in the "Machine Design Manual". According to the different structure of the part to be matched, it can be divided into A, B, C, D, E, F. Such marking is not a simple "groove width". ×diameter" or "groove width×groove depth"

for reference!




Use "groove width x diameter" when the diameter must be guaranteed.

      Similarly, when the groove depth must be guaranteed, "groove width x groove depth" is used.

      Although the same results may be obtained, the benchmarks and concepts are different.

      When groove width×diameter: the base of groove depth is the center line.

      When groove width×groove depth: the reference of groove depth is the contour line.


      Prompt according to GB4458.4 (Mechanical Drawing Size Note Method):

      In the figure, A and B belong to the general injection method of pin and shaft undercut, you can choose one of them.

      In the figure, C belongs to the general notation of undercut for non-shaft.