Why does it say 'the tool will not fit' and why were some areas left uncarved?

Why this happens

1. The tool diameter is equal to or bigger than the narrowest gap in the selected vectors. A 0.125" end mill cannot enter a 0.102" opening, and an exact 0.125" opening may also be skipped because the software needs clearance.
2. Overlapping or intersecting vectors confuse the region logic, so areas that look fine get skipped.
3. Open or duplicated vectors in the selection.

The fix

1. Identify the narrowest feature and pick a tool smaller than it, or use a V-bit, which fits any width (its effective diameter is zero at the tip).
2. Clean the geometry: weld or trim overlapping shapes, and run the Vector Validator to find intersections, duplicates, and zero-length spans.
3. For pockets with mixed wide and narrow areas, use two tools in one pocket toolpath: a large clearance tool plus a small detail tool that reaches the tight spots.

Pro tips

• Skipped letters specifically usually mean bad glyph outlines (self-intersections from a font conversion). See the "random letters didn't carve" entry.
• The software measures the fit against the vector, not the material, and an "unfittable" region can be skipped silently in some toolpath types, so always scan the preview before cutting.