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What size do I machine a part to before plating?

Last updated 10 August 2026

Smaller than the print, by twice the per-side coat thickness on a both-sided diameter. A half inch journal at plus or minus a thousandth, plated .0002 to .0005 per side, has to be machined to .4986 / .5000.

Three things move the number and a spreadsheet that subtracts the coat thickness once gets all three wrong. The feature has two sides, so a diameter moves by twice the per-side figure. The direction reverses between an outside diameter and a bore. And the plater quotes a window rather than a number, so the band you get to work in is narrower than the band on the print.

That last one is the expensive one. The part has to be in specification whichever thickness comes back, so the width of the plater's range comes straight out of your tolerance before anyone has cut anything.

Worked

On the print.4990 / .5010 in
ProcessPlating
Per side0.0002 to 0.0005 in
The dimension getslarger at this operation
Pitch diameter shift per unit of per-side effect2 times
Hold before the process.4986 / .5000 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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