This is a question we get asked on a regular basis. The reason people want printed threads varies. Some customers find it less time consuming than drilling and tapping from scratch, some find it handy for fixing the part into a machining jig and others use it as a feature of their specific part.
We print a lot of threads at RAM3D and in most cases they require chasing with a tap.
This helps clean the major and minor diameter surface which can have grains of powder left in them. This creates a tapped thread rather than a machine spec thread.
Some customers will add the threads to their parts themselves and other customers only put a tapping drill hole in their part to let us add the thread feature. This incurs a small extra fee for our additional time, so it is optional if the customer prefers to finish the part themselves. If a thread is required, let us know so we can add it accordingly.
Are there any issues printing coarse threads such as M60x3 or printing finer threads such as M35x1?
The answer is most threads can be printed down to an M3, after that they are too fine.
We can print most sizes and types.
Correct Thread Modelling
One issue we come across, is where the customer has added a cosmetic thread and when we bring in the file it appears as just a hole. This is often caused when using automated hole features in a CAD program. Threads need to be modelled so carefully look at your model to ensure the thread has actually cut into the part.
With 3D printing, the CAD model supplied is what should print. This applies with chamfers to lead into the thread. If you are adding a thread, start by adding your holes at the desired root diameter, then add a chamfer to start the hole. We use the pitch of the thread/2 then add 0.1mm. If we are doing a M6x1mm thread we would add a 0.6mm chamfer. This works well to give a nice clean lead in to the thread, however, you can play with this to make it suit.
If your CAD software cannot model threads we can add them to your 3D model. We can add threads to the following file formats, .stp, .step, .x_t or .sldprt