I ve been trying to create a m18x1.5 internal thread using helix cut command but I couldn't create the cut at the correct place. I added some images to help you to understand the problem im facing.
So I would like to create a thread up to the end of the bigger hole shown below. I just created a simple triangle to illustrate the thread. I created a centre line which the cut will revolve around and chose pitch as 1.5. but the cut has been created outside of the small hole. l want it to begin from the hexagon till the end of the bigger hole.
do it the other way round.
First create the inner hole diameter from which You will cut away the helix for thread.
Same way as in reality.
They used geometry is generating IMHO a Non-Manifold Body situation due to the fact that the upper triangle line is tangent to Your cylinder, where tolerance issue will arrise (this is an assumption of me)