This is a continuation of the article How to Model Threads Part One.
Once the helix is created as the path for the Swept Cut, the profile sketch for cutting the threads will need to be designed. I like to think of this as the design of my cutting tool. This can best be done as a triangular sketch with the tip cut off (observe the trapezoidal shape in the picture placed horizontally). The small flat edge on the left is for the necessary required root flat, this is referenced in the thread standard. The included angle is defined as the angle between the two cutting edges of your tool. For most thread types the included angle is 60 degrees which can be seen in the pictured cutting tool sketch. The .07 length of the side of the trapezoid represents the length necessary for the thread to cut all of the way to the open pocket where the drilling hole was made.
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What was really crucial, more than the sketch of the cutting tool, was the placement of the sketch. This sketch was placed on a plane that intersected the center point of the helix. This plane also is at a 90 degree perpendicular to the end point of the helix. I set the endpoint of the helix perpendicular by changing the start angle of the helix to 185 degrees as mentioned in the previous section of this article. If this plane is not perpendicular to the endpoint of the helix it will make for an inaccurate cut of the thread due to the fact that the cutting tool is not at a 90 degree perpendicular. It is easiest to think of it just like it would be on your machine in real life, so without perpendicular placement of the cutting tool you would end up with a cut thread that has a skew in the dimensions. Also, if you take a look at the sketch pictured above you will notice that a pierce relation has been added to the sketch. The pierce relation is symbolized by the orange square with the blue dot on it; this can be seen on the upper left hand corner of the sketch pictured above. This is a not necessarily an everyday used relation, and many users may be unfamiliar with it. What the pierce relation is used for is to achieve a real 3D contact condition where the 2D coincident relation will not suffice. This relation is perfect for thread creation because as the sketch revolves and travels up or down along the path, the pierce relation will assure that the sketch remains placed correctly on the path. Something worth mentioning: notice how my profile and path for the sweep start off of the solid part in open space. The reason this was done is to give me a nice clean entry point with a smooth transition where my threads begin on the part. If I had just gone ahead and started the profile and path at the bottom edge of my part it would have given me an abrupt start without a smooth transition at the start of my threads.
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In the end, all that is left is to apply the Swept Cut feature. Upon opening up the Swept Cut feature it will ask you for a profile and a path selection. When the correct boxes are populated with your sketch of your cutting tool as the profile and the helix as your path, SOLIDWORKS will do all of the heavy lifting and create your usable 3D threads (you can see a reference of this in the picture above). From here you are all ready to go and 3D print your part with real threads, or go and run a simulation of the threads in your part. The final part with threads is pictured below.
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Link to Modeling Threads Part One blog article.