[Za...] Posted October 19, 2020 Share Posted October 19, 2020 Hello all, My first question is, what is the correct way to show this True Position GD&T callout in calypso? As of right now, I have it as a Position callout to the scan of the minor diameter based on the Base Alignment (since no datums are referenced). I just want to make sure this is correct, because I have another issue that is related to this. The 2nd issue is the .940 locations... The X & Z locations measure within tolerance, but the true position callouts fail. How are the X/Z locations different for the TP callouts when they are both based on the same secondary alignment? Any help is appreciated. Thanks, Zach Link to comment Share on other sites More sharing options...
[Mi...] Posted October 19, 2020 Share Posted October 19, 2020 With no datums referenced and the callout applied to a hole pattern, I believe the position only applies to the 4 holes relative to each other. See the example on the right side, below. Really, there should be a basic 1.880" in x and y between holes, if that's the case. I think you'll need to use the Bore Pattern True Position characteristic for it. Link to comment Share on other sites More sharing options...
[Za...] Posted October 19, 2020 Author Share Posted October 19, 2020 Please sign in to view this quote. Something like this? Link to comment Share on other sites More sharing options...
[Mi...] Posted October 19, 2020 Share Posted October 19, 2020 Please sign in to view this quote. I believe so, yes. Though I don't have a huge amount of experience with the Bore Pattern fit, unfortunately. Also, in answer to your second question, you would get a difference if you're evaluating them as cylinders. The X- an Z-values are just measured to each cylinder's origin. The Position measurement accounts for the full length of each cylinder, so if they're out of square the position will be worse. Link to comment Share on other sites More sharing options...
[Za...] Posted October 19, 2020 Author Share Posted October 19, 2020 Please sign in to view this quote. I have minimal experience with the Bore Pattern fit, but I feel pretty comfortable that this is correct. Oh and I am definitely evaluating the 1/4-20 threads as cylinders. Maybe I'll switch to circles and see where it goes since none of the other callouts for those threads require a cylinder to evaluate. Thanks for your help Michael, I definitely appreciate the response. Link to comment Share on other sites More sharing options...
[Mi...] Posted October 19, 2020 Share Posted October 19, 2020 Please sign in to view this quote. No problem. Also, it's totally fair to evaluate them as cylinders - technically that is what the print requires. The only catch is that, at least in my experience, tapped holes as cylinders are very hard to get to repeat, so it may not be accurate. It's also another thing I don't have much experience with. You might try measuring threaded inserts instead if possible. Link to comment Share on other sites More sharing options...
[Za...] Posted October 20, 2020 Author Share Posted October 20, 2020 Please sign in to view this quote. That makes sense; the readings I get on thread scans are "meh" at best. I was going to go the threaded inserts route, but I just realized we don't have that size for whatever reason. Seems too common to not have, but here we are 🤣. Thanks again for the help, Zach Link to comment Share on other sites More sharing options...
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