J
I am looking for advice from people who calibrate gage blocks and feel they do a good job (in terms of being realistic with uncertainty, capabilities and what you tell your customers).
I recently sent out a grade 2 set of gage blocks for calibration (as I have each year for the past 5 or 6 years).
The report came back showing measuriment results and the associated uncertainty (which is good since I sent it to a lab accreidted by A2LA to ISO 17025).
For a 1 inch gage block, my block had a reading of +1 uin. The labs uncertainty was (3.4 + 2L)uin which is 5.4uin at 1 in.
No matter which spec the vendor used (his cert was not very specific which is another issue), the uncertainty makes it possible that the block would be out of tolerance. This made me go look at a bunch of other uncertanties for gage blocks on other accreditation scopes and I found the same issue. Most uncertainties for commercial calibration labs are larger that the gage block tolerances.
How do these labs determine in tolerance or out of tolerance conditions (or do they)?
Should they all just tell their customers up front to ignore the grade and look at their uncertainty because the report has no real possibility of saying that they meet an actual grade? The customer can then decide what they need.
Should they then tell their customers that they will only reject a block if the reading is so far off that even the uncertainty does not make it possible for it to be in tolerance?
Any thoughts would be appreciated.
Thank you!
I recently sent out a grade 2 set of gage blocks for calibration (as I have each year for the past 5 or 6 years).
The report came back showing measuriment results and the associated uncertainty (which is good since I sent it to a lab accreidted by A2LA to ISO 17025).
For a 1 inch gage block, my block had a reading of +1 uin. The labs uncertainty was (3.4 + 2L)uin which is 5.4uin at 1 in.
No matter which spec the vendor used (his cert was not very specific which is another issue), the uncertainty makes it possible that the block would be out of tolerance. This made me go look at a bunch of other uncertanties for gage blocks on other accreditation scopes and I found the same issue. Most uncertainties for commercial calibration labs are larger that the gage block tolerances.
How do these labs determine in tolerance or out of tolerance conditions (or do they)?
Should they all just tell their customers up front to ignore the grade and look at their uncertainty because the report has no real possibility of saying that they meet an actual grade? The customer can then decide what they need.
Should they then tell their customers that they will only reject a block if the reading is so far off that even the uncertainty does not make it possible for it to be in tolerance?
Any thoughts would be appreciated.
Thank you!