True position without diamter
True position without diamter
(OP)
There is some disagreement among engineers at my work in the calculation of true position without a diameter call-out. Given an open ended datum notch with the following tolerances:
Width .100 +/-.002
Drop from base of slot to datum surface is 1.267+/-.005
[TRUE POSITION|.006|E|F] (with basic dimensioning to datum points on datums E & F)
When calculating the true position without a diametric symbol is it necessary to double the positional measurement?
ie. if the position checks .0084 from nominal is this a true position of .0084 (.0024 O/T), or is it a true position of .0168 (.0108 O/T)?
Jeanne
Width .100 +/-.002
Drop from base of slot to datum surface is 1.267+/-.005
[TRUE POSITION|.006|E|F] (with basic dimensioning to datum points on datums E & F)
When calculating the true position without a diametric symbol is it necessary to double the positional measurement?
ie. if the position checks .0084 from nominal is this a true position of .0084 (.0024 O/T), or is it a true position of .0168 (.0108 O/T)?
Jeanne





RE: True position without diamter
Thus, the feature in question can only be .003 from nominal, in either direction. That's where the .006 comes from.
If a diameter symbol were included, then it would be allowed .003 from nominal, in any radial direction (.006 total diameter tolerance). Of course for your situation the diameter wouldn't make sense. But the numbers work the same, only the shape is different.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: True position without diamter
Jeanne
RE: True position without diamter
For other applications a rectangular zone can make sense.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: True position without diamter
Dave D.
www.qmsi.ca
RE: True position without diamter
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com