How to create a two or more thread starts in Solidworks:
1 – Create a circular sketch matching the external diameter of a cylinder which you want to make a thread, in my case I needed to develop a special metric thread with a 80mm diameter, 3.5mm pitch and 15mm length, it also needed to have three entrances clockwise.
2 -Turn the sketch into a curve helix-spiral and then choose the desired pitch-height, in my case, I utilized a 10.5 pitch, the reason I used such a high pitch is because I needed the three thread starts maintaining the original 3.5 pitch.
So basically 3.5 (pitch) x 3 (thread starts) = 10.5 pitch
If you don’t compensate the additional thread starts in the pitch value the thread will revolve against itself rendering it useless. You can use any pitch height you want, in my case I needed a 17mm as maximum height.
Altura = height
Passo = pitch
3 –Create the thread profile as you wish, since I needed a non standardized metric pitch I had to use a formula to find out the height, major diameter, minor diameter etc.
4 - Cut the thread profile using cut sweep, use the thread profile and the helix to generate the cut.
Here is how it should look like after the cut
5 – Now simply use circular pattern and use 3 instances to create the 3 desired thread starts.
The finished part