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IATF Calibration Question

Discussion in 'IATF 16949:2016 - Automotive Quality Systems' started by Marty Keenan, Aug 31, 2020.

  1. Steven Severt

    Steven Severt Member

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    If you are using them to make a decision on the dimensions with wide-open tolerances, I would suggest getting them calibrated. People often do verification before use on micrometers, calipers, etc., then will do periodic calibrations that are kept on record. The verifications, in this instance, would be testing the tools against a master part before using them for the day or shift. You still have to know have traceability back to national or international standards and a reaction plan for what happens when you find that the results of the verification did not meet expectations. It's probably easier to show that you've met requirements and have confidence in your measurements that you're using to release product to just have them periodically calibrated.

    I've never really understood the reference only thing. I spent a couple of years in a small machine shop after many years in automotive, and this is what everyone wanted to do there too. They would put reference only stickers on V-blocks, parallels, etc., but then would use these tools to complete measurements that were used to make decisions on the acceptance of material. This just seemed like a crazy practice to me. I was glad to get back to the automotive world where everything makes sense.
     
  2. Eric Twiname

    Eric Twiname Well-Known Member

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    I agree that this is an oft used and inappropriate 'bypass' of the concern, but I have had several instances where "Reference only" labels made sense.
    All of those cases are instances where a typical measuring tool was NOT used for measurement, but for process control.

    Case1: a granite surface plate used to set a process orifice...we didn't care what the gap was, we cared of the thickness that came out of it...and close enough was indeed close enough.
    Case2: The same 'process orifice' was adjusted using micrometer heads...but again, we didn't care what the mic heads said...only the resulting thickness.
    The resulting thickness was measured using a calibrated gage, then the orifice adjusted as needed.
    The mic heads used for adjusting the orifice could have been fine pitch screws and done the same job...

    If the resulting product thickness was measured by "reference only" mics, then we would have had a problem...

    We defined in the process docs what things must be calibrated, and what things didn't, and why...it was cheaper to write the explanations into the doc than to try to explain it to every auditor who came by and saw a mic head...
     
  3. Golfman25

    Golfman25 Well-Known Member

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    Case 3: A ruler used to do an "eyeball" check on the width of a coil to determine if it is 3 or 3.5 inches.
    Case 4: The old caliper on my desk, used for a reference check when someone asks about correction of an out of spec dimension.
     
  4. Eric Twiname

    Eric Twiname Well-Known Member

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    LOL...your call of course (to an extent)...

    Case 3 seems like you internally trying to figure out what somebody handed you...sorta like your eyes not being "calibrated" to color...
    Case 4 seems to have a decision based on the data...I'd manage the calibration period out to 10yrs, but have it "calibrated"... but that's me.

    It's so easy to manage cal cycles based on reality, I wonder why folks bang their heads against this topic so often.
     
  5. Golfman25

    Golfman25 Well-Known Member

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    Case 4, we never make decisions based on a caliper. If we have to split hairs, we'll go to the CMM. But it's pretty heavy to carry into my office. :)
     
  6. Eric Twiname

    Eric Twiname Well-Known Member

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    Not questioning you...well, I sorta am by definition since there are question marks used...so, not trying to disagree with you or pick a fight...

    If you don't make a decision based on the caliper, what's the point of having it or using it?

    More of a curiosity for posterity on the chain than anything else...
     
  7. Golfman25

    Golfman25 Well-Known Member

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    Because it's quick and easy. Can fit in my pocket, and take right to the press. Gives us an idea if we are at the high or low side of the tolerance. Can tell if a part is egg shaped, or if we are measuring over a burr or perhaps a taper of some sort. We can then work from there to bring the parts into tolerance.
     
  8. Eric Twiname

    Eric Twiname Well-Known Member

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    prior to measuring on a more reliable gage as needed...

    Totally right there with you...thanks for clarifying. (again for "posterity")

    Triage doesn't need calibration...formal decisions do. I 100% agree.