Creating Thread Gaging for Internal Threads
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  1. #1
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    Exclamation Creating Thread Gaging for Internal Threads

    I've got a 4 1/4-12 3B internal thread I need to make a plug gauge for. I've got the machinery handbook however I'm having a hard time understanding everything going on in it.If someone could throw me the dimensions for the Go/NotGo plug gauge required to check this internal thread properly, that would help a lot. Then I can work backwards to figure it out and teach myself in the future how to do it. I'm just pressed for time right now and we can't get the gauge for over a week, we need to run parts today. Thanks ahead of time!

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    Some one more knowledgeable may come in and lambast me but this is how I do it. Caveat: I know my parts and products and know how the threads are used and that there is no life safety concerns. Threads for me are there to hold components together and typically only must support the weight of an assembly. If this is for a lifting device or holding pressure used only certified gages!

    That being said - 4.25"-12 un (60° V - thread) Maj dia max 4.248 to 4.2366 - PD 4.1939 to 4.1874 - Over .045 wires - 4.2567 to 4.2502.

    For the go I'd thread to nominal and for the no go I'd put it at about .002 over , over the wires. Good luck- use a dissimilar material. For infrequent use I like 630 bronze if it's going to be used a lot I like prehardened 416 stainless.
    Last edited by Kingbob; 06-22-2021 at 10:56 AM. Reason: Also read it as 4 & 1/2

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    Is this a one time thing? Is this for your use or a customer? If it's a one time use and for a customer I try to see if they'll give me a mating part and are ok with me using it as a go gage. Otherwise for Plug gages we do min major diameter and min pitch diameter for the go, and max pitch diameter with min major diameter on the no go.

    Thread Basics: Go / No-Go Acceptance | 2018-01-01 | Quality Magazine

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    I've made this mistake before. The male plug gauge needs to be made to the female pitch diameter numbers.

    4.250"-12 3B

    Pitch Ø: 4.1959"/4.2023"
    Major Ø: 4.2500"/4.2685" Ref.

    The low side is your GO, the high side is your No-GO. I made a gauge in the past to the male numbers, which gives you no clearance on the thread.


    Ref:
    4.250"-12 3A

    Pitch Ø: 4.1959"/4.1910"
    Major Ø: 4.2500"/4.2386"


    Edit: First read this as 4.500"-12, not 4.250"-12.

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    This is a one time deal, though they talked about "if it were a really nice gage" they would consider heat treating it and etching a gage # on it for future use. Which I don't agree with as this is aerospace and we don't have certifications to be doing such thing.

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    Quote Originally Posted by aerowizard View Post
    This is a one time deal, though they talked about "if it were a really nice gage" they would consider heat treating it and etching a gage # on it for future use. Which I don't agree with as this is aerospace and we don't have certifications to be doing such thing.
    If it's Aerospace, you definitely need a certified/calibrated gage otherwise I can see this biting you in the ass later on. Just tell the customer (in not so many words), you want a good part, we are waiting on the proper inspection equipments-GO-NOGO gage....

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    Nothing to do with gages but this website is really useful for thread calculations.

    UN imperial screw thread calculator

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    Quote Originally Posted by Kingbob View Post
    Some one more knowledgeable may come in and lambast me but this is how I do it. Caveat: I know my parts and products and know how the threads are used and that there is no life safety concerns. Threads for me are there to hold components together and typically only must support the weight of an assembly. If this is for a lifting device or holding pressure used only certified gages!

    That being said - 4.25"-12 un (60° V - thread) Maj dia max 4.248 to 4.2366 - PD 4.1939 to 4.1874 - Over .045 wires - 4.2567 to 4.2502.

    For the go I'd thread to nominal and for the no go I'd put it at about .002 over , over the wires. Good luck- use a dissimilar material. For infrequent use I like 630 bronze if it's going to be used a lot I like prehardened 416 stainless.
    Hey kingbob I just picked up a Kingston hq 1440 I read in another thread you had one it’s missing the change gears and the charts I was needing some pictures and tooth counts so I can make replacements.


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