posted 07 July 1999 09:52 PM               

http://Elsmar.com/ubb/Forum1/HTML/000089.html

http://Elsmar.com/ubb/Forum1/HTML/000144.html

http://Elsmar.com/ubb/Forum4/HTML/000036.html

http://Elsmar.com/ubb/Forum4/HTML/000047.html

http://Elsmar.com/ubb/Forum4/HTML/000073.html

http://Elsmar.com/ubb/Forum27/HTML/000000.html

Regards,
Don

posted 08 July 1999 11:06 PM               

There is:

Equipment (Gage) Variation (EV), and
Appraiser Variation (AV)

Let's say your EV is 10% and your AV is 15%. You have 25% of your tolerance taken up in variation.

posted 17 July 1999 07:17 PM               

Also at NIST, check out: www.physics.nist.gov/cuu/Uncertainty/index.html

posted 09 March 2000 02:54 PM               

Uncertainty Budget for Thread Pitch Diameter Calibration

Reproducibility: The reproducibility was calculated from thirty readings (10 each from three technicians) utilizing gage blocks, thread wires, super-micrometer and a 1-14 UNS-2A thread set plug. The standard deviation for the reproducibility was calculated at 11.6 micro-inches (.0000116ä).

Should add the uncertainty of the S-mic when recâd - Resolution: The resolution of the super-micrometer providing the value for measurement over wires is 10 micro-inches. We assume a rectangular distribution, that is, the error is equally likely to be any value between 0 & 10uä. The guide to measurement uncertainty instructs to divide by the square root of three to convert a rectangular distribution to one standard deviation of 5.77 micro-inches.

Gage blocks: The blocks used in the calibration of plug gage diameters are grade one. In the calibration of a 1ä thread plug gage we need only the 1ä gage blocks. We will assume that the block value can be anywhere within the +/- 2uä tolerance of the block. We will also allow this tolerance to expand by the 1.3uä (1/2 of the k=2 value) uncertainty reported on the gage block certification. Therefore the gage block tolerance plus the uncertainty was divided by the square root of three to get to one standard deviation of 1.91 micro-inch.
2ä gage block at 2.94 micro-inch (from1.1 & 4)
3ä gage block at 3.64 micro-inch (from 1.3 & 5)
4ä gage block at 5.25 micro-inch (from 3.1 & 6)
5ä gage block at 11.7 micro-inch (from 1.1 & 4, 1.3 & 5)
6ä gage block at 14.2 micro-inch (from 1.4 & 4, 3.1 & 6)
7ä gage block at 15.4 micro-inch (from 1.3 & 5, 3.1 & 6)
8ä gage block at 18.7 micro-inch (from 1.3 & 2, 1.3 & 5, 3.1 & 6)
9ä gage block at 20.5 micro-inch (from 1.1 & 4, 1.3 & 5, 3.1 & 6)
10ä gage block at 24.1 micro-inch (from 1.3 & 2, 1.1 & 4, 1.3 & 5, 3.1 & 6)

Thread wires: Wires used were supplied at size with an uncertainty value of 12 micro-inches. As this value is reported at two standard deviations will bring to one standard deviation for the completion of this budget.

Force applied: A reproducibility study was conducted on the effect of force in relation to the digital values displayed on the super-micrometer. The study consisted of three operators with ten readings each. This test produced a standard deviation of 5 micro-inches.

Anvil parallelism: The super-micrometers anvils have a parallelism requirement of 20 micro-inches of which is routinely verified through calibration. Assuming the worst condition and a rectangular distribution, we can arrive at one standard deviation of 11.55 micro-inches.

Temperature: The gage blocks used are made of chromium carbide which carries a coefficient of expansion that is approximately 4.7 x 10-6. The majority of thread plug gages cycling through our metrology lab are made primarily of steel which carries a coefficient of expansion that is approximately 6.4 x 10-6. For the purpose of this study we will use the 1ä block size. We will assume that all components have been stabilized to the room environment of 68o +/- 1o F. As the temperature sensing device has itâs own uncertainty of 05 o, we will use 1.05o temperature error. In this scenario we receive an error of 4.9 micro-inches on the block and 6.7 micro-inches on the thread plug gage. Using the difference of we can provide a rectangular distribution and arrive at one standard deviation of 1.04 micro-inches.
2ä, 1.05 o change = 3.5 with one std. dev. of 2.0 micro-inch
3ä, 1.05 o change = 5.4 with one std. dev. of 3.1 micro-inch
4ä, 1.05 o change = 7.2 with one std. dev. of 4.2 micro-inch
5ä, 1.05 o change = 8.9 with one std. dev. of 5.1 micro-inch
6ä, 1.05 o change = 10.7 with one std. dev. of 6.2 micro-inch
7ä, 1.05 o change = 12.5 with one std. dev. of 7.2 micro-inch
8ä, 1.05 o change = 14.3 with one std. dev. of 8.3 micro-inch
9ä, 1.05 o change = 16.1 with one std. dev. of 9.3 micro-inch
10ä, 1.05 o change = 17.8 with one std. dev. of 10.3 micro-inch

Uncertainty Budget for Thread Pitch Diameter Calibration

All Values expressed in micro-inches

Source ofUncertainty Standard Deviation Limits Uncertaintyãuä ãu2ä
Reproducibility (A) 11.6 134.56
Gage blocks 1.3 2 1.91 3.648
Thread wires 12 6 36
Resolution 10 5.77 33.293
Force (A) 5 25
Anvil parallelism 20 11.55 132.25
Temperature 1.8 1.04 1.082

Sum = 365.833
Combined uncertainty, uc = 19.127
Expanded uncertainty, U = 38.3
2ä pitch diameter Expanded uncertainty, U = 38.7
3ä pitch diameter Expanded uncertainty, U = 39.2
4ä pitch diameter Expanded uncertainty, U = 40.3
5ä pitch diameter Expanded uncertainty, U = 45.8
6ä pitch diameter Expanded uncertainty, U = 49.0
7ä pitch diameter Expanded uncertainty, U = 51.0
8ä pitch diameter Expanded uncertainty, U = 55.8
9ä pitch diameter Expanded uncertainty, U = 58.9
10ä pitch diameter Expanded uncertainty, U = 64.7

posted 07 May 2000 02:09 PM               

quote:

---

Originally posted by Dawn:
Is there some way to determine the uncertinty right off the Gage R & R calculations?
And how would you suggest we state it in every work instruction? Thanks!!!!!

---

posted 19 May 2000 09:11 PM              

To this end, there is a FREEWARE uncertainty calculator program available. It was developed at Compaq Metrology, and conforms to ANSI/NCSL Z540-2 and the GUM. The program is in two parts, to ease installation from floppy disks.

Go to http://www.proficiency.org and click the "Software Download" page. The program is "Uncertainty Calculator 2.5".

The program will not teach you the ins and outs of uncertainty budgets, such as proper distribution for contributors or effective degrees of freedom, but it does make the calculation process very simple once you do have the knowledge.

I hope this helps.