Why did my pocket leave material behind: islands in the middle or round corners?

Why this happens

1. Round corners are physics: a spinning round tool can never produce a sharp inside corner. Every inside corner gets a fillet of the tool radius.
2. Islands and uncleared areas: the tool is too big to enter narrow regions of the pocket, or the stepover is too large and leaves cusps between passes.
3. In two-tool pockets, the path is computed around the larger tool's reach, so if the "detail" tool isn't actually smaller, tight areas stay uncleared.

The fix

1. Use two tools in the Pocket form: a large clearance tool for the open area plus a genuinely smaller detail tool for corners and narrow channels.
2. Stepover of about 40 to 50% of tool diameter is a common starting point for flat-bottomed pockets (shop advice). Larger stepovers leave visible ridges on the floor.
3. For square inside corners you have three options: accept the fillet, add dogbone or T-bone fillets to the vectors (for joinery fit), or run a V-bit "squaring" pass in the corners for cosmetic sharpness.
4. If islands persist, drop the clearance tool a size.

Pro tips

• Floor ridges that show only in raking light: take a final full-area pass at the same depth (spring pass) or 0.01" deeper.
• An Offset pocket strategy leaves fewer direction-change marks than Raster in visible work; Raster is often faster in big open areas.