huangyhg

During a conversation with a colleague the other day the subject of verification of out of tolerance dimensions came up.

Company requirements state that inspection tools used to verify dimensions must be capable of measuring 10X the precision of the dimension called out on drawings
Case 1: Drawing specifies a dimension to be .245 -.250 and you use a micrometer capable of measuring to .0001 increments. When inspecting the part you get a measurement of .2501, should the part be rejected or accepted?
Case 2: Drawing specifies a dimension to be .245 -.250 and you use a CMM to verify part dimensions. The CMM reports the part measurement to be .25001, should the part be rejected or accepted?
My stance is that to verify that the dimensional value meets the tolerance on the drawing it makes sense to use tooling capable of measuring 10X precision of the dimensions called out on the drawing. Without using 10X precision tooling then you get rounding error in the tool, correct? It seems to me that by being required to use 10X precision tooling I must verify out to that level of precision the part meets the drawing. My colleague feels that I have exceeded the intent of the drawing by measuring out to 4 places and should not reject the part. In the case when using the CMM I feel that you should truncate the dimensional values to 10X precision of the drawing dimensions and that any characters after the 10 precision should be ignored.
I have also been part of conversations with different opinions that if you specify a dimension on a drawing as .24 - .25 the criteria for part acceptance is different than if I specified the dimension as .240 - .250
Any thoughts?
Thanks



18 days ago

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