In general, this is a treatise on designing printable helical threads.
Many of us know how to use parametric 3D modelers that can easily and precisely define any number of common elements that are easily scaled to any scale needed.
Solidworks is a widely used application where basic information can help you to make any thread you want for your design.
For the rest of us, we hope someone will post up something useful so we can carve and hammer things into useful shapes and objects. I am hoping this release will provide such for your "larger than usual thread requirements.".
And for those who could care less about design but love to print interesting things...
This print is for you too!
I dare to print this and put it down to be forgotten.
Treatise on 3D Printed Screw Threads
You will find that the attached file is based on a mean-1" thread with an 8-tpi helix.
The hex edges are cut to 45 degrees rather than the conventional 30 degrees.
The thread chamfer is 60 degrees for easy engagement.
This design departs from conventional screw threads in that, for one, the threads are "rolled". Secondly, the shape of the thread has a 90 degree head instead of a more conventional 60 degree edge. Note the means of managing the clearance regardless of scale.
Consider that we are mostly dealing with radial clearance due to the layering nature of 3D printing. This allows us to use the very same profile with only a clearance offset between the internal and external thread design.
This part easily scales but please consider scaling consistently in all 3 directions to preserve the 45 degree overhangs.
One last element I discovered, and is useful as it is in keeping with gear definitions:
With screw threads, we size them based on the maximum OD. In gears, we have to use a "pitch diameter" for scaling gear ratios. What is interesting with this design is that the centerlines of the valley radii all line up to define a pitch diameter. Knowing this really makes defining screw threads in parametric CAD much simpler between mating parts. This is why I say this thread is a mean-1" diameter thread. It is equivalent to how pitch diameter in gears are defined. See the second section image for clarification.
It is my hope that there is enough data in the STL to use in facet modelers to graft the thread into your own design.
The offset between the two parts within the STL is 2".
I've included the master Solidworks file (2016) for those who can make use of it.