Cosmetic threads

Dear all,

I have got a question about creating cosmetic threads. I have an object with a hole of 16mm. I would like to create a thread on this hole. If add a cosmetic thread it only allows me to make M18x.. and no M16x...  Is this normal?

When I then make the part that has to go into this hole, I can only choose M18x.. when I make it 18mm in diameter and not if I make it 16mm.

Finally, if I try to assemble them, the second part is larger than the first part and they do not nicely fit.

I might be doing something stupid, but could anyone help me out on how to make a thread in a 16mm hole and make the correct part to fit into the hole?

Thanks a lot.

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