Last updated 10 August 2026
Open it. A 3/8-16 UNC-2B tapped hole plated .0002 to .0005 per side has to be cut to .3364 / .3409 on pitch diameter, which is above the print rather than below it.
An external thread being plated is cut small so the coating brings it up. An internal thread is the mirror: the coating grows inward off both flanks and closes the pitch diameter, so the tap has to leave it open. The four times factor is unchanged, because it comes from the flank angle rather than from which side of the material you are on.
The symptom of getting this backwards is a plated part whose bolt will not start, on a hole that gauged correctly before it went out. By then the plating is on and the recovery is stripping and re-plating the whole lot, which is why this is worth a minute before the job runs rather than after.
| On the print | .3344 / .3401 in |
|---|---|
| Process | Plating |
| The feature | thread, both surfaces in the process |
| Per side | 0.0002 to 0.0005 in |
| The dimension moves | smaller at this operation |
| Shift per unit of per-side effect | 4 times |
| Hold before the process | .3364 / .3409 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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