Are you trying to save cost?  Hassle?  Annually is the typical interval, but I suppose you are right that there wouldn't be much wear against plastic parts.

Regards,

Cory

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Calibration intervals are selectable by the user and I agree with CoryPad that typically annual recertifications are common.  We take under consideration frequency of use, and importance of the feature being accurate (relates to gage r&r) for considering intervals.  You might also consider the types of filler's if any used in your plastic parts as some such as glass fill can be quite abrasive.

Regards

I have been contemplating bumping up the interval for years and value your inputs. One thing that I have done is to issue select gages for high abrasive plastics. These, I will keep on an annual interval.

Regards

GeneO,

Most calibration standards like ANSI Z-540 handle calibration intervals based on the calibration history of the gage.  In other words, if, over the last five years (or whatever interval you want), there have not been any instances of a thread gage coming back 'Out of Tolerance', you have the justification to increase the interval.  Contarily, if 10% of the thread gages are coming back out of tolerance then the interval should be shortened to increase the reliability.  

At our plant we use 95% acceptance to justify extending an interval and 90% acceptance to mandate shortening an interval.

JR97

Do you have a thread micrometer that you could chek the thread gage with?

if you do, and you keep it calibrated every year, you could verify the accuracy of the gage every so often. Of course this is more for male gages, not sure if there is anything for female gages. figure keep the micrometer calibrated to check the other gages, less cost.