Micrometer Calibration Procedure - Please critique

M

mooser

#11
Another way to check the parallel is with a calibrated ball. Without rotating the ball check the surface of the anvils in 4 or 5 areas. The parallel should be within the manufacture's specifications.
mooser
 
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J

John Nabors - 2009

#12
I'm right there with gpainter, CarolX and Kevin H. Get your calibration person(s) certified as Certified Calibration Technicians through the ASQ and you don't have to write work instructions that specify what angle the tech's pinkie finger should be wrapped around the frame of the mic. All you then have to do is specify that the cal is performed by a certified tech and that the standards used are NIST traceable and then be able to prove to an auditor that you are in conformance with these requirements.

An ounce of verifiable competency is worth pages and pages of level II and level III documentation.
 

Jim Wynne

Staff member
Admin
#13
I'm right there with gpainter, CarolX and Kevin H. Get your calibration person(s) certified as Certified Calibration Technicians through the ASQ and you don't have to write work instructions that specify what angle the tech's pinkie finger should be wrapped around the frame of the mic. All you then have to do is specify that the cal is performed by a certified tech and that the standards used are NIST traceable and then be able to prove to an auditor that you are in conformance with these requirements.

An ounce of verifiable competency is worth pages and pages of level II and level III documentation.
The "verifiable competency," in the form of ASQ certification, is subjective at best, and near-worthless at worst, especially as it applies to calibration. As far as I can see, there's nothing in the calibration BOK that deals with the nitty-gritty of calibration of mechanical devices. Work instructions should serve two purposes. The main purpose is the obvious one (to provide instructions for users) but the other one--to establish a standard for performing a task, is just as important, and can't be avoided by having "certified" people.
 
S

sabrinalim

#15
May I piggy back and ask questions on the attached file? The Micrometer accuracy specification were taken from GGG-C-105C. Can I assume that this Federal Standards has been obsoleted but ISO9000 still allows us to refer to its specifications for calibration purposes.

Also when we do inhouse calibration for the micrometer, we compare the master values to the measured values. The difference in the two values shows us the error in the micrometer. Should this error value be less than the values in the 3rd column in the standards - Error in Indicated Measurement (max) - or should be less than the sum of the error values from the 3rd and 4th columns (Error in Indicated Measurement (Max) and Permissible Flexure (max))? Assume th micrometer has no error in flatness and parellelism.
Thanx
 
U

Umang Vidyarthi

#16
Good beginning.....

I would add "exercising" the mic to watch for skipping or sticking which indicates the need for cleaning.....

Add the need for white gloves and have the instructions state that they must be used to pick up the gage blocks - NEVER touch gage blocks with your fingers.....

Add the requirement to document the specific path for comparison and where to find the procedure to calculate measurement uncertainty.....under international definitions for traceability, there must be an unbroken chain of comparisons to National or international standards, and there to SI and must have stated uncertenties at each step, or you do not have traceability.....

As always I strongly suggest sending items for calibration to a cal lab accredited to ANS/ISO/IEC 17025.....while I understand cost issues, metrology professionals are the best folks to handle your calibration.....

Hope this helps.

Hershal
It does help,a very useful piece of advice.:agree1:

The "verifiable competency," in the form of ASQ certification, is subjective at best, and near-worthless at worst, especially as it applies to calibration. As far as I can see, there's nothing in the calibration BOK that deals with the nitty-gritty of calibration of mechanical devices. Work instructions should serve two purposes. The main purpose is the obvious one (to provide instructions for users) but the other one--to establish a standard for performing a task, is just as important, and can't be avoided by having "certified" people.
Well stated Jim,without mincing words(as usual).Instructions and proceedures form the system,and no human is supposed to supercede this;certified or qualified personnels can not and should not be permitted to over ride the system. :yes:
 

harry

Super Moderator
#17
May I piggy back and ask questions on the attached file? The Micrometer accuracy specification were taken from GGG-C-105C. Can I assume that this Federal Standards has been obsoleted but ISO9000 still allows us to refer to its specifications for calibration purposes.

Also when we do inhouse calibration for the micrometer, we compare the master values to the measured values. The difference in the two values shows us the error in the micrometer. Should this error value be less than the values in the 3rd column in the standards - Error in Indicated Measurement (max) - or should be less than the sum of the error values from the 3rd and 4th columns (Error in Indicated Measurement (Max) and Permissible Flexure (max))? Assume th micrometer has no error in flatness and parellelism.
Thanx
Welcome Sabrina,

Are you facing problem attaching the file or you had forgotten to do so?
 
S

sabrinalim

#18
No Harry, I'm still refering to the original file Micrometer.doc that Atetsade posted right at the beginningof this thread.

regards
 
J

jfgunn

#19
Why reinvent the wheel? There are several sources of good (already written) procedures. Note that "good" and "already written" don't always go together.

I might suggest purchasing ASME B90.1.13-2001 since it is the national standard for micrometers. Note that includes how they should be manufactuered. When you reference it at the procedure, you might consider a statement like:

ASME B90.1.13-2001 Appendix C except C2.5 & C3.3 where Sections C2.5 and C3.3 might be the flatness and parallelism that you mentioned you might skip.

Another source might be procedures available from GIDEP. www.gidep.org

If you are not familiar with GIDEP, you may want to take a look. It can save you some time in writing procedures.

Joe
 
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