The correct way to read an analog gage is???

Hello everyone

Say that I have a part with a feature that is supposed to measure 0.111 +/- .001 according to the drawing.

The gage I am using to measure this has an accuracy of 0.0000

Would a reading of .1121 be acceptable? Would .1126? The argument here at work is (Eng.) the gage is capable of measuring to .0000 so we SHOULD take advantage of that and use tighter measurment. The other side (QA) says that although the gage is capable, the feature is only designed to .000 so nothing past the third decimal place should matter.

Is there any guidance out there on this?

Thanks

[Marc]

Take a look at:

http://Elsmar.com/ubb/Forum5/HTML/000027.html

[Don Winton]

elbee,

Welcome to the Cove.

I may be mistaken in this. The implied purpose of measuring to a significant digit in excess of the specification is to determine exactly what you are asking. IMHO, if the specification is 0.111 +/- 0.001, then 0.1121 is NONCONFORMING. To mirror Marc’s suggestion, it is more important to meet the intent of the specification. Do not become caught up in the ‘goal=post’ method of thinking.

The other side (QA) says that although the gage is capable, the feature is only designed to 0.000 so nothing past the third decimal place should matter.

I disagree. Ask your phone company when one minute equals one minute. Perhaps the QA department is more concerned with meeting the letter of the specification rather than the intent of the specification. Just a thought.

Regards,
Don


[This message has been edited by Don Winton (edited 01-09-99).]

[ljreimer]

IF the tolerance of the device is 0.111 ±0.001 then 0.112 would be acceptable, to take advantage of the measuring device that has an accuracy of ±0.0001 if that is really the accuracy, many gages have resolutions of ±0.0001 but the resolution of the gage does not always support an accuacy equal to resolution.

Lookup the accuracy of the device to verify that is will produce an accuracy of ±0.0001. An device of this accuracy will be subject to temperature conditions at the time of measurement due to change of mass.

when the readings and the tolerances of the device are close to pass/fail requirments, review the data history on this device should help