[SH...] Posted April 12, 2021 Share Posted April 12, 2021 It is a good idea to use MMC on threads , I was advised to not use MMC on threads because we can't calculate the minor diameter of thread accurately.IMG_20210412_211221.jpg Link to comment Share on other sites More sharing options...
[Aa...] Posted April 12, 2021 Share Posted April 12, 2021 Please sign in to view this quote. From section 2.9 of Y14.5-2009, "Each tolerance of orientation or position and datum reference specified for a screw thread applies to the axis of the thread derived from the pitch cylinder." THe problem is not that you can't measure the minor diameter accurately, but that you can't measure the pitch diameter accurately. Link to comment Share on other sites More sharing options...
[SH...] Posted April 12, 2021 Author Share Posted April 12, 2021 Please sign in to view this quote. Pitch cylinder is a tall order 😮 . I have witnessed drawing that is clearly specified tp for minor diameter ,don't remember it was ASME or ISO. Link to comment Share on other sites More sharing options...
[Th...] Posted April 12, 2021 Share Posted April 12, 2021 The same section in 14.5 allows specifying major or minor diameter if necessary. Link to comment Share on other sites More sharing options...
[Aa...] Posted April 12, 2021 Share Posted April 12, 2021 Please sign in to view this quote. Agreed. Please sign in to view this quote. Yes, that was likely done to accomodate the limitations of available measuring equipment and methods. Link to comment Share on other sites More sharing options...
[SH...] Posted April 12, 2021 Author Share Posted April 12, 2021 I have passed my true position without MMC on threads.. Thanks to datum shift 🙂 Link to comment Share on other sites More sharing options...
[Je...] Posted April 12, 2021 Share Posted April 12, 2021 Please sign in to view this quote. . . Thanks for sharing, Shabu. I have had the same issues with position for threads. Have you ever tried flexible hole locators? They're an extra expense, but sometimes we can persuade the customer to provide them as a tooling expense during the quoting process. Here's an example: https://www.mscdirect.com/browse/tnpla/ ... G3EALw_wcB . . Link to comment Share on other sites More sharing options...
[Aa...] Posted April 13, 2021 Share Posted April 13, 2021 I don't know a lot about flexible thread plugs, but I do know we did a study on the kind with a shoulder, and had wholly unsatisfactory results.True Position Locators.pdf Link to comment Share on other sites More sharing options...
[To...] Posted April 13, 2021 Share Posted April 13, 2021 Here's a study done by Ryan Stauffer Link to comment Share on other sites More sharing options...
[Ke...] Posted April 13, 2021 Share Posted April 13, 2021 I have used both styles of Threaded Hole Location gages (solid & split types, from different manufacturers), and have gotten good correlation between them. Also, we were able to get good correlation on a between my measurements, and two different suppliers; each using a different brand of gage. The split types are nice, because you don't need to worry about over-tightening them, as they do not need to be tightened to the shoulder, to be accurate and effective. The drawback of the split types, is the difficulty of finding someone who can calibrate them; of course, you can always treat them as a disposable item, and just throw them away after a specific time, or amount of use. *Note* we only use Threaded Hole Location gages on tapped holes that are too small to probe the pitch diameter, directly. I have not had the opportunity to test direct measurements vs Threaded Hole Location gages. Link to comment Share on other sites More sharing options...
[Ke...] Posted April 13, 2021 Share Posted April 13, 2021 Please sign in to view this quote. Oops? Link to comment Share on other sites More sharing options...
[SH...] Posted April 13, 2021 Author Share Posted April 13, 2021 Please sign in to view this quote. I think this one....Threaded_Holes_metrology_conf_2011 (1).pdf Link to comment Share on other sites More sharing options...
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