From: "James R. Lloyd"
Subject: RE: Calibration Environment/Lemieux/Lloyd
Couple of questions first Kevin .... What do you mean by micrometer standards? I take it you mean the end user micrometers, etc... usually when I hear the term "standard" Im thinking of Calibration Laboratory level equipment such as gage blocks, parallel flats, and optical parallels used to calibrate outside micrometers .... As far as environmental effects on "floor" usage micrometers, it depends upon your resolution and accuracy requirements that you need on the floor. If I remember correctly expansion coefficients for steel are something like 1 micro inch (.000001) per degree F per inch, this is typically miniscule in most machining type environments. Considering that your typical micrometer is usually calibrated to an accuracy of +/- .001 inches, if your measurements are only in this range it would take some SERIOUS and I mean SERIOUS changes in temperature before the measurement accuracy of your floor micrometers would be affected.
The main concern for Micrometers on a floor is mishandling, and abuse that can affect the measurement accuracy rather than the environment.
For the calibration of Micrometers a bit more environmental control is required, not so much for the micrometer, but for the standards used to calibrate it. Referencing an USAF Metrology Procedure for micrometers .... There are three primary attributes that are calibrated ... measurement accuracy/linearity, flatness of the anvil and the spindle, and parallelism between the anvil and spindle. An acceptable environment to calibrate you typical +/- .001 0-1 inch micrometer would be even 75-79 degrees as the gage blocks would certainly not expand to a degree that would be even measurable ... but the larger the micrometer measurement the more likely that expansion WILL affect its calibration. Usually this threshold is around 4-5 inch micrometers, where you would need an environment controlled to about 71 +/- 4 degrees, and even this becomes excessive with micrometers that measure 10-11 inches where the optimum dimensional calibration environment of 68+/- 1 is required.
I hope I didn't inundate you with information, but metrology, and calibration programs are my specialty.
Best Regards
James Lloyd
QA Manager
Wesport Steel and Supply Inc.
One Comment, I hope all the other mics that are not calibrated are still
identified in your M&TE inventory and identified/labeled as "Not
Calibrated", regardless of use they are still M&TE and must be identified
and controlled.
-----Original Message-----
> From: Kevin Lemieux
Require information regarding consensus on what environmental parameters should calibration be carried out in? What do others do with their micrometer standards so they are protected as well as available for shop floor usage? We currently have calibration tractability on two sets of standards which are available for shop personnel usage. This eliminates the requirement to calibrate all personal standards. The question has came up on the environment in relation to temperature and location of the generally used standards. Help?
> Kevin - QA Manager
Subject: RE: Calibration Environment/Lemieux/Lloyd
Couple of questions first Kevin .... What do you mean by micrometer standards? I take it you mean the end user micrometers, etc... usually when I hear the term "standard" Im thinking of Calibration Laboratory level equipment such as gage blocks, parallel flats, and optical parallels used to calibrate outside micrometers .... As far as environmental effects on "floor" usage micrometers, it depends upon your resolution and accuracy requirements that you need on the floor. If I remember correctly expansion coefficients for steel are something like 1 micro inch (.000001) per degree F per inch, this is typically miniscule in most machining type environments. Considering that your typical micrometer is usually calibrated to an accuracy of +/- .001 inches, if your measurements are only in this range it would take some SERIOUS and I mean SERIOUS changes in temperature before the measurement accuracy of your floor micrometers would be affected.
The main concern for Micrometers on a floor is mishandling, and abuse that can affect the measurement accuracy rather than the environment.
For the calibration of Micrometers a bit more environmental control is required, not so much for the micrometer, but for the standards used to calibrate it. Referencing an USAF Metrology Procedure for micrometers .... There are three primary attributes that are calibrated ... measurement accuracy/linearity, flatness of the anvil and the spindle, and parallelism between the anvil and spindle. An acceptable environment to calibrate you typical +/- .001 0-1 inch micrometer would be even 75-79 degrees as the gage blocks would certainly not expand to a degree that would be even measurable ... but the larger the micrometer measurement the more likely that expansion WILL affect its calibration. Usually this threshold is around 4-5 inch micrometers, where you would need an environment controlled to about 71 +/- 4 degrees, and even this becomes excessive with micrometers that measure 10-11 inches where the optimum dimensional calibration environment of 68+/- 1 is required.
I hope I didn't inundate you with information, but metrology, and calibration programs are my specialty.
Best Regards
James Lloyd
QA Manager
Wesport Steel and Supply Inc.
One Comment, I hope all the other mics that are not calibrated are still
identified in your M&TE inventory and identified/labeled as "Not
Calibrated", regardless of use they are still M&TE and must be identified
and controlled.
-----Original Message-----
> From: Kevin Lemieux
Require information regarding consensus on what environmental parameters should calibration be carried out in? What do others do with their micrometer standards so they are protected as well as available for shop floor usage? We currently have calibration tractability on two sets of standards which are available for shop personnel usage. This eliminates the requirement to calibrate all personal standards. The question has came up on the environment in relation to temperature and location of the generally used standards. Help?
> Kevin - QA Manager