What is the proper way to apply GD&T to a box thread with an internal sealing surface?
What is the proper way to apply GD&T to a box thread with an internal sealing surface?
(OP)
I apologize if this is a repeat thread but I could not find the answer I was looking for. In the file I attached is there a proper method to apply a geometric dimension based on the Face Square To Thread note. I would like the shoulder to be perpendicular to the thread so that when the corresponding part is threaded into this coupling a face seal is achieved. Thanks in advance for any help you can give me.





RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
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RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
Do not apply datums to axes. I count six features, any one of which could define the centre axis. The thread has a minor, pitch and major diameter. EWH's suggestion sounds good to me.
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JHG
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
It may be a matter of semantics, but isn’t attaching a datum symbol to any one of the three thread pitch diameters simply making the axis of that feature a datum? Just asking.
And to clarify, although I did not say it as you did, I did not mean to attach the symbol to the axis on the drawing because as you said there are multiple features that could be used to get this "axis".
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
Attaching a datum to one of the thread diameters makes the centre axis of the thread your reference geometry. Ask yourself how somebody is going pick this feature up. I try very hard to not use threads as datums.
You are assuming that the other diameters are centred perfectly on the thread. I would not assume that. Will the thread minor diameter be centred perfectly on the pitch diameter and the major diameter?
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JHG
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
FYI: my interepration of your initial reply "Do not apply datums to axis" seemed contraditory to what attaching a datum flag to a diameter dimension indicates, doesn't it?
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
If you say "FACE SQUARE TO THREAD" then thread is your datum and face is your controlled feature.
In your comment you say " had thought of that too but I am not to sure how to verify that during inspection."
So, how YOU think the requirement will be verified during inspection? Also, exactly how square?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
The OD of your part can be a datum and it's centerline would then be the axis of that datum.
See Y14.5-2009 paragraph 4.8.2 for clarification. It states in part "The datum feature symbol identifies physical
features and shall not be applied to center lines, center planes, or axes."
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
A datum is a theoretically perfect axis (or plane, line, point, or combination of these).
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
I still stand by what I had meant to convey... a centerline is not a datum, but can be a datum axis derived from a datum feature.
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
It may be better to say that a center line should never be labeled as a datum. (A center line can indeed be a datum, but I see that you were referring to the "datum feature symbol.")
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?
Otherwise, I think (???) you are specifiying a square tolerance zone.
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RE: What is the proper way to apply GD&T to a box thread with an internal sealing surface?