I would like to get some help with a dispute about the correct way to measure a hole pattern with a Composite Feature Control Frame. The attached spreadsheet has the actual measurements and nominal dimensions, which are BASIC and all extend from the datums, i.e., primary (A), secondary (B) and tertiary (C). It should be possible to calculate these and determine conformance even without a drawing. All replies will be greatly appreciated.
There should be at least two separate sets of measurements.. For the upper horizontal frame specified tolerance the X and Y data are compared to the referenced datums as well as a top and bottom of the features of size measurements for orientation verification.
For the lower horizontal feature control frame there should be a separate set of X Y measurements relative to the specified datum and to a reference pattern feature.
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Kelly, thanks for your reply. Yes, there should be two separate sets of measurements (which doesn't show in my data because I just did the math on a calculator for the feature-to-feature data). I'm not sure what you mean in your second paragraph, "relative to the specified datum and to a reference pattern feature". The specified data in the Feature-Related Tolerance Zone Framework (FRTZF) is for orientation only, not location. Location in the FRTZF is related to feature-to-feature within the pattern. I don't know if that's what you mean by "a reference pattern feature". Thanks again.
Last edited by quality_auditor; 12-29-2016 at 11:54 AM.
The specified feature tolerances are orientated only to the reference datums however there is a feature to feature requirement per the FRTZF.Originally Posted by quality_auditor
In general and for simplicity, establish the datum orientation then zero to one of the pattern features. Measure the rest of the features relative to that zero feature.. All should position verify to and within the specified geometric tolerance given within the FRTZF.
Tell me and I forget. Teach me and I remember. Involve me and I learn.
Yes, you are completely correct. Although, I don't make the extra step of zeroing on the first, or any other, hole. I just do as you say, measure the features relative to each other. But, we interpret the requirement the same way. If you have the time, have you tried to calculate the data in my spreadsheet? If you could, I would appreciate an opportunity to compare our results. I am disputing with several of my colleagues who don't see it our way. Thanks.
We have a tools on Engineers Edge that will allow you and others ~ to quickly calculate the as-measured geometric tolerances.
https://www.engineersedge.com/tolerance_chart.htm
https://www.engineersedge.com/true_position.htm
https://www.engineersedge.com/calcul...sition_pop.htm
If there are challenges within your team you may consider one of my books on GD&T.
Geometric Boundaries - ASME Y14.5-1994
Geometric Boundaries SI - ASME Y14.5-1994
Geometric Boundaries II - ASME Y14.5-2009
Geometric Boundaries II SI - ASME Y14.5-2009
Geometrical Boundaries - ISO 1101
Geometric Metrology - Dimensional Tolerancing inspection and Practices in Manufacturing
These books are available in hard copy or online via premium membership on Engineers Edge.
https://www.engineersedge.com/geomet...ies-2-book.htm
https://www.engineersedge.com/member...neers-edge.htm
Tell me and I forget. Teach me and I remember. Involve me and I learn.
Also, there is a Composite Position Tolerance GD&T Calculator for Dimensional Inspection available that can calculate to your requirements.
https://www.engineersedge.com/mechan...ance_13871.htm
It does require an Engineers Edge Premium Membership account.
Tell me and I forget. Teach me and I remember. Involve me and I learn.
Can't do the work yourself?
Works great -> https://www.engineersedge.com/mechan...ance_13871.htm
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