In our Calibration lab, we differentiate Pins and Plugs primarily by how we report the measured data on our customers certification.
Pins are generally described as a set, say, .250 to .500 in. as either a plus set or minus set, usually ZZ class. Plug gauges are usually individual or a small Go, No-Go set put together by the customer and are generally tighter tolerances, for example a Deltronic plug gauge, which has a tolerance of + 40, -0 µin. However, if an ordinary pin gage is sent in individually, we will calibrate it as a Plug gage.
The diference:
For a “Pin Gage Set”, we do not report individual data, we simply verify that each pin in within it’s tolerance along it’s length on all sides. Any pin that is out of tolerance is noted with the deviation reported.
For a “Plug Gauge”, we give data for both ends and middle on two axis, so a total of 6 data points are recorded and included on the certification. Accordingly, we charge more for plug gauges than for pin gauges. Some of our customers request that entire pin gauge sets be calibrated as plug gauges so they have the data.
On a side note: regarding calibrating only once, pins and plugs can grow!! I have seen even .500 in pins grow as much as 200 µin over a few years of annual calibration. If they are not annealed properly, the molecules relax over time and the gauge will grow out of tolerance.
Does any of this make sense?
