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X
In this example we will create the thread on an oil filler cap.
It is not a recommended practice to create thread features on standard fasteners.
But in this case we need detailed threads to create a mold.
We cannot use the NX Thread command, because this is not a standard thread.
We will use the Helix and Bridge Curve commands to create the thread path.
Then we will sketch the thread section on the helix, and sweep the thread with the Variational
Sweep command.
We first model the cap without the threads.
Next, we hide the solid body and display the WCS because NX creates helix curves relative
to the WCS.
From the Insert Curve menu, choose Helix.
Enter point 95 to create just less than one full turn.
And set pitch to 4 millimeters.
For the Radius Method, select Use Law.
Select the Linear Law Function.
Enter Start and End values to create a helix that tapers between 13 point 5 and 15.
Next we move the WCS 4 millimeters in the Z direction.
And create a second helix curve.
Enter 4 for the number of turns.
And set a constant radius of 15 millimeters.
To connect the helix curves, create a Bridge Curve.
The Bridge Curve creates a tangent chain of curves that we can use to sweep a section
along one continuous path.
To create the thread profile, we define a Sketch on Path near the end of the helix.
Make sure the Selection Intent Curve Rule is set to Tangent Curves.
In our sketch we constrain the vertical line to remain centered on the path, and parallel
to the Z axis of the datum coordinate system.
Use the Variational Sweep command to sweep the section.
You don’t need to reselect the path, because the section was sketched on the path.
To complete the thread, we trim the end with a plane using the Trim Body command.
Unite the two solid bodies together to complete the model.
Consider these additional points.
We created the thread so that it overlaps slightly with the existing part.
We could have used the Swept command instead of Variational Sweep.
With Swept, use the Vector Direction Orientation Method to keep the thread profile aligned
with the Z axis.
We can’t use the Sweep Along Guide command, because it does not provide enough control
over the orientation of the swept section.