Last updated 10 August 2026
Smaller than the print. A .375 bore at plus or minus a thousandth, ground .0025 per side, wants .3690 / .3710 before the grinder.
Two reversals stack here and people usually get one of them and miss the other. Grinding removes material, so the part arrives at the grinder further from finish than it leaves. And the feature is a bore, so removing material makes the dimension bigger rather than smaller. The two together put the pre-grind hole under the print, which is the opposite of the pre-plate hole on the same drawing.
A part with a plated journal and a ground bore on it therefore has one feature that starts oversize and one that starts undersize, from the same nominal, on the same traveler. That is a normal part, not a contrived one, and it is why a single rule of thumb applied down a column of features produces scrap.
| On the print | .3740 / .3760 in |
|---|---|
| Process | Grinding |
| The feature | diameter, both surfaces in the process |
| Per side | 0.0025 in |
| The dimension moves | larger at this operation |
| Shift per unit of per-side effect | 2 times |
| Hold before the process | .3690 / .3710 in |
Open this case in the calculator, and change the numbers.
Computed by ctrlPlanner. MIL-STD-870, Federal Screw Thread Specification H28.
This is one characteristic. A real part has forty of them through five operations, and every one needs the same walk when the drawing revises. That is what ctrlPlanner does from a ballooned print.
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