Hi Guy, re:
> Thank's Michael. How are you seeing those needle alignment issues?

Yeah like Burr writes above it seems to be after the boolean.

- Michael

Got another diff issue. I'm trying to diff the green screw thread with the main body to leave a female screw thread but when I diff it the entire body disappears.

Hi Guy, coiled objects like your screw thread here can be difficult due to the underlying surfaces overlapping each other from one coil to the next.

Try with the attached version, I split your thread object into 4 quadrants using Edit > Trim and then used ShrinkTrimmedSrf on it.

- Michael

Thanks Michael,

Why did you have to split the thread into object into 4 quadrants?

Hi Guy,

re:
> Why did you have to split the thread into object into 4 quadrants?

Because that removes the condition that is failing which has something to do with having underlying surfaces that overlap each other.

- Michael

Hi Guy,

Another trick is to scale everything so that the size of the threaded object is around 50 units (rather than 6 mm), do the boolean, and then scale it back down.

- Peer

Ahh that's easier, thank you.