A
ASpecialKindOf
Question: When a thread ring gage is adjusted by an outside calibration lab, with a cert that shows before and after PD measurements, how do I assess whether or not product gaged with this ring was impacted by the "before" setting? This is asked in a 'covered for an audit' context.
I know that direct measurement is not the "correct," or ASME B1.3 accepted, method, and even though actuals are given, the lab lists set plugs as their masters on their ring gage certs. I don't know if the lab uses these measurements or set plug drag to determine that the gages require adjustment. I assume the actuals are found with a CMM.
It'd be nice if they would state a judgement based on drag, as I do when I calibrate thread ring gages in house on truncated set plugs. If I find a ring a bit looser than I desire, I note whether the ring is free spinning, or still has some drag. Or if I find a ring a bit tighter than I desire, I note whether the ring binds on the plug, or is able to thread the full form section. In my opinion this fulfills the intention of calibrating and setting an adjustable ring gage to a master.
Seeing as how direct measurement is not an acceptable calibration method for thread rings, how do I interpret the direct measurement results? I would like a cut-off point, a % of tolerance amount, where a reinspection of stock will be required. But I know that line of thinking has problems, because variation in pitch, lead and flank may make a ring that is just a little loose seem really loose when only PD actuals are examined. Should I use the labs cert stated uncertainty for PD as a cut-off point?
I need a line in the sand. If I don't have this, I feel as though all outside labs ring gage adjustments should be treated as gage failures requiring reinspection and/or customer notification. The other option is to act like these adjustments do not matter, and assume that none of these adjustments were critical (spinning loose, binding tight), which is not an assumption I can make in good faith.
I've scoured online resources and cannot find this topic answered. I don't really understand why not when I know others must sometimes have thread rings adjusted at outside labs.
--Sorry for the lengthy post, I hope someone can help me on this. This topic has been bothering me a long time and is of real importance to me. Thank you for your time.--
I know that direct measurement is not the "correct," or ASME B1.3 accepted, method, and even though actuals are given, the lab lists set plugs as their masters on their ring gage certs. I don't know if the lab uses these measurements or set plug drag to determine that the gages require adjustment. I assume the actuals are found with a CMM.
It'd be nice if they would state a judgement based on drag, as I do when I calibrate thread ring gages in house on truncated set plugs. If I find a ring a bit looser than I desire, I note whether the ring is free spinning, or still has some drag. Or if I find a ring a bit tighter than I desire, I note whether the ring binds on the plug, or is able to thread the full form section. In my opinion this fulfills the intention of calibrating and setting an adjustable ring gage to a master.
Seeing as how direct measurement is not an acceptable calibration method for thread rings, how do I interpret the direct measurement results? I would like a cut-off point, a % of tolerance amount, where a reinspection of stock will be required. But I know that line of thinking has problems, because variation in pitch, lead and flank may make a ring that is just a little loose seem really loose when only PD actuals are examined. Should I use the labs cert stated uncertainty for PD as a cut-off point?
I need a line in the sand. If I don't have this, I feel as though all outside labs ring gage adjustments should be treated as gage failures requiring reinspection and/or customer notification. The other option is to act like these adjustments do not matter, and assume that none of these adjustments were critical (spinning loose, binding tight), which is not an assumption I can make in good faith.
I've scoured online resources and cannot find this topic answered. I don't really understand why not when I know others must sometimes have thread rings adjusted at outside labs.
--Sorry for the lengthy post, I hope someone can help me on this. This topic has been bothering me a long time and is of real importance to me. Thank you for your time.--