[Al...] Posted March 14, 2022 Share Posted March 14, 2022 Hello all, I'm fairly new to metrology and to CMM programming and would like to get a better understanding of some basic measurement tasks. I have a part which is an aluminum casting with no CAD model. There are no datums or GD&T on the print, only basic dimensions with tolerances. I need to measure the width of a slot which is specified as 0.500 +- .01 inches. The slot is visibly different widths throughout its length; It has a draft angle and there are various irregularities on the walls of the slot. Measuring it with a digital caliper shows variations of around +- 0.01 inch depending on where in the slot the measurement is taken. My questions are: How would you go about measuring this on a CMM and why? How would you report these results to the customer? There are similar threads with helpful information but I'm hoping to get some explanations that might help me understand some of these basic concepts that aren't quite clicking yet. Any help is very much appreciated, thank you! Link to comment Share on other sites More sharing options...
[An...] Posted March 15, 2022 Share Posted March 15, 2022 can you post a drawing for better understanding? Link to comment Share on other sites More sharing options...
[Ri...] Posted March 15, 2022 Share Posted March 15, 2022 This would be a great case for using the Symmetry Plane and showing the 2 Point distance, so you can track the deviations across the length of the slot. If you want fit/function, the OTE will tell what you need to know. Link to comment Share on other sites More sharing options...
[Al...] Posted March 15, 2022 Author Share Posted March 15, 2022 Andreas, I won't be able to post a drawing, but it's just a slot punched in a cast part. The basic dimension shows the width of the slot as .500" +- .01". My question could apply to any distance taken between two lines or planes; I'm mostly wondering about best practices and the rationale for using different methods (symmetry planes/points, caliper/cartesian distance from line-to-line or point-to-point) as well as how to handle reporting something like this. Richard, Thank you, the Symmetry Plane & 2-point distance seems like a great solution to me. I'm surprised I haven't come across the 2-point distance characteristic yet. Link to comment Share on other sites More sharing options...
[Ri...] Posted March 15, 2022 Share Posted March 15, 2022 The 2 Point Distance for Symmetry Planes is new to 2021. It's been a long time coming, but it is a great tool. Link to comment Share on other sites More sharing options...
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