Thank you for your reply

However, I discovered where the problem is

The threads does show when you right click the view and choose "show thread feautres" or "display threaded feautres" (I can't remember what exactly the phrase is)

Concerning the problem with hatching,, the washer lower phase was mated with the cover upper face with no offset
When i used an offset of even .0001mm (which does never appear in print), the cover hatched correctly...
I can't understand why, but this is the solution
If somebody can explain what technically causes this, it will be appreciated

Thanks