Boolean Difference completely deleting target surface

I’m just trying to boolean difference the text in this file to get an engraving on the interior of the ring. For some reason whenever I try it’s deleting the whole inside surface and I’m not sure why.
Any help is appreciated :slight_smile:

File: Example.3dm (16.4 MB)

I think the reason is because the letters go through the ring. I reduced the height of the letters and it worked.