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Gauge verification

Discussion in 'Gage Calibration and Uncertainty' started by shazwan, Mar 9, 2018.

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How to verified Thread Ring Gauge?

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  1. shazwan

    shazwan New Member

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    Hi all, I need help. It this ok if i use thread plug gauge to verify thread ring gauge?

    Item need to verify: 1/4-36UNS-2A
    Method to verify: 1/4-36UNS-2B
    Frequency of verification: Everyday

    hope anyone can help me:)
     
  2. ncwalker

    ncwalker Well-Known Member

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    To illustrate the complexity of what you are asking, I have attached the layout of all the features of a thread from the Machinery's Handbook. The point is this - on either gage, one end will be manufactured to the LMC and the other to the MMC. To certify the gage, you need to know that it is indeed at these two states (less a bit of gage maker tolerance).

    You are calling the plug gauge the "master". How are you using it? The no-go end of the plug gage (MMC) into the go ring (MMC for the female thread)? What if the no-go end of the plug gage has worn, and is NOT at MMC? It will go in, will it not? What if the go end of the ring gage has worn? The no-go end of the plug gage will go in. But shouldn't it go in anyway (they should be line to line contact, less gage makers tolerance)?

    If you dropped one of them and were looking for burrs or damage, this may be a reasonable thing to do. But it is not a substitution for calibration. Where you are looking at physical numbers. If you could make a statement from historical data as to how quickly they wear and you were using this to monitor when it went for a "real" check, I'd be OK with this method for a daily check which would look for gross errors, such as the thing was dropped and damage. But to truly verify it, you need to send it out to be checked.

    Now, let's talk reality. This can be costly. It can be MORE costly than just replacing the darn thing with a new one. Brand new, they aren't that expensive. So hear is a trick that may help you ... they are silver in color, typically. You can have them coated with Titanium Nitride (TiN) which will color them gold. Why? The coating is high wear and imperceptibly thin. The advantage here is - when you wear off the TiN coating, you will see the silver below it (very obvious). You know it's worn through use - time for a new gage. I'd only use this in very high wear situations, however. But it's something to think about.
     

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