Last updated 10 August 2026
About .005 on the diameter, .008 if cleanup is in doubt. A half inch journal ground to plus or minus a thousandth wants .5040 / .5060 before the grinder.
Grinding runs the same arithmetic as plating in the opposite direction: the part arrives at the grinder larger than it leaves, so the upstream limits are bigger rather than smaller.
How much you actually need depends on how far out of round the part comes in. Bar stock is usually two or three thousandths out; a part that has been through heat treat can be far worse and is the reason the number is a range rather than a figure. Leave too little and the grinder cannot clean up; leave too much and you are paying grinder time to remove metal a lathe could have taken off.
| On the print | .4990 / .5010 in |
|---|---|
| Process | Grinding |
| Per side | 0.0025 in |
| The dimension gets | smaller at this operation |
| Pitch diameter shift per unit of per-side effect | 2 times |
| Hold before the process | .5040 / .5060 in |
Open this case in the calculator, and change the numbers.
Computed by ctrlPlanner. MIL-STD-870, Federal Screw Thread Specification H28.