Hi Satoribomb,

There is a small mis-alignment between these 2 shapes:




Intersections with overlapping pieces and along shared tangents tends to be a delicate area, and small misalignments like this tend to make the calculations much more difficult, even between pretty simple shapes.

If you delete the cylinder and draw a new one snapped directly on to points of the box (just with Draw solid / Cylinder), then those will boolean together ok - I have attached the redrawn cylinder here as Trimmer_fixed.zip .

But still after that, that piece won't boolean difference away from the main body - there is a different sort of problem with the main body that I will explain in just a minute in another post.

- Michael