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Profile depth of a thread?


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Engineering wants the end (depth) of a thread profiled.
There is a dia. 1.250 shaft with a 1.25-12 thread halfway down the shaft with no shoulder (essentially both with the same diameter).
There is a dimension from the (threaded) end of the shaft to the bottom of the thread cut.
He is asking if it is possible to profile the end 'point' at the bottom of the threads to the DRF.
The depth dimension is 'critical' to a perpendicular datum plane.
Looks impractical to me. Any other opinions?
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I thought a gage might be needed. We try to avoid building gages. Calling it a nut makes it sound a lot simpler. It would have to have zero lead-in at the bottom, so it lined up.
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Sounds like good advice. In this case he's asking for a single point, which I'm surprised is a profile option. Does profile for a single point come up often? That's a new one for me. I also expected intersection points would be an option since points are ok, but apparently profile doesn't work the same for intersections.
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I performed testing on this method about 15 years ago.
We used a threaded Tooling Ball Gage and ground the end of the thread to be a complete thread.
What we found was:
1. It could measure the depth with some inaccuracy.
2. The inaccuracy was due to the full thread of the Tooling Ball coming in contact with the imperfect thread of the feature would cause the Tooling Ball Gage to tilt slightly. It created sine error in the depth measurement. Basically it took a Right Triangle measurement and create an Oblique Triangle measurement.
2a. Unlike a Bolt, when used, it should never reach the imperfect thread. The Bolt will create perpendicularity itself once face to face contact is achieved (Assuming all geometry is normal).
(My PaintCAD isn't as good as it once was 😱 )

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