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Accuracy

Accuracy
Does the 4 to 1 rule apply to Portable CMM measuring accuracy, how do I best explain this to my superiors? The arm we use states a length accuracy of .016microns or .00062 inches so do I multiply this x 4 = .0025 and tell them that the expected accuracy of the arm would be this? Hence trying to verify position tolerances of .05 micron might be a stretch of the arms capability, even though I can repeat good measurements on a 20,’’ Weber gage within .0005 Every time no matter where I place it in the reach of the arm, this would include the Z axis.

I said that I could say with out a doubt we could verify position tolerances within .2 microns or .008’’, and I would not want them to lose work over my statement if I am not correct
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  • Bill, I'm interested in what the spec of your arm is. If it is as bad as you say and still in spec, thats the way it goes. If its measuring out of spec, why would you expect it to be accurate at all?

    I know we have had this argument before but it is exactly the reason we have standards such as the B89.4.22 so that customers are protected.
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  • Bill, I'm interested in what the spec of your arm is. If it is as bad as you say and still in spec, thats the way it goes. If its measuring out of spec, why would you expect it to be accurate at all?

    I know we have had this argument before but it is exactly the reason we have standards such as the B89.4.22 so that customers are protected.
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