What Bernina do you have? I think Bernina uses Mettler to set all the factory settings on the Bernina. I forgot what weight and fiber....all machine manufacturer's pick a standard thread to for their machines. The King Tut is a way thicker thread so I would think you would need to do some top thread tension adjustments also to use the King Tut. And I agree with the suggestion to change the needle for the King Tut and try a larger eye.