I am trying to make a Key cover for 3D printing. I modelled the shape of the key that needs to be inside the cover and wanted to add a boolean to make a hole in the shape of that key.
Applying object scale makes the object data (mesh) dimensions match the object and what is shown in the viewport. That’s important because tools and modifiers use object data dimensions
Have to make normals consistent for the cylinder (in edit mode) and the key has a lot of double geometry. Selecting all, W -> remove doubles gets rid of those. Merge distance for that now also operates on correct dimensions because object scale was applied.
The first one looks like it’s going in the right direction, although it’s not creating a negative space in the cilinder.
Deleting the faces leaves me with the edges, but no possible way to extrude downwards. I tried to Join both objects, but that doesn’t seem to do it either.
Don’t crop images. You’re not telling blender version, viewport view, and possibly modifier and some object info by doing that and since there’s no updated .blend, can only guess what you’re showing and what could go wrong. But I’m not going to, this should be simple enough.
Do those mentioned things in order
first apply object scale, object mode, ctrl+A -> scale
then edit mode, select all, W -> remove doubles
still everything selected, ctrl+N
for both objects
When boolean difference is working, it won’t remove the cutting object from view or otherwise. You have to hide it to see the result. Could hide it from the outliner (top right) by disabling the eye icon, or select the object and H to hide (alt+H to unhide).
Boolean modifier behaviour after mentioned fixes. Top viewport and top modifier when the modifier is on the key, and lower ones for when it’s on the cylinder.
A video to show the steps using only menus and the tool shelf