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What do the nut hole dimensions in mechanical drawings mean?

1. The basic size of M4 table thread is 4 mm, F represents the basic deviation, and 6 represents the accuracy level of level six. Judging from the thickness, the size of the two small holes is only 14-6=8mm, so the three holes are through holes. The hole thread depth is 8mm.

2. From the side view, the hole depth of 12 is 9 mm.

3. The hole in the middle is a stepped hole. The size of a large hole is 12 mm and the size of a small hole is 9.5 mm. There are dimensional tolerances.