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ISO 2768 general tolerances
A dimension with no tolerance on the drawing is still toleranced. Find its limits from the class in the title block.
28.4 in class m → 28.2 to 28.6OpenISO 286 limits and fits
H7, g6, p6: the deviations in microns and the limits in millimetres, for the diameter of your dimension.
⌀25 H7 → 25.000 to 25.021OpenClearance and interference
A hole and a shaft assembled together: does it slide, does it grip, and by how much.
⌀40 H7/g6 → 9 to 50 µm clearanceOpenMetric threads
The tapping drill, the pitch, the pitch diameter and the clearance hole, from M1.6 to M64.
M8 → ⌀6.8 drillOpenSurface finish
Classes N1 to N12, their exact Ra, the typical Rz range and the processes that produce them.
N7 → Ra 1.6 µmOpenWhy these tools are free
Because they come out of the software. CoteCote reads a mechanical drawing and applies these rules itself, across dozens of dimensions at once: the tables of fits, the general tolerance classes, the roughness symbols. Putting them out here costs us nothing and is useful.
The values are exactly the ones the software applies, from the same formulas and the same tables. You'll never find one figure here and a different one in an inspection report.
If you catch yourself coming back to these pages often, you're probably doing by hand what CoteCote does on its own. See what it can do, or ask for the ten-day trial.