🔍 The difference is the direction they eject chips and the finish they leave on the workpiece. An **up-cut** spiral bit pulls chips **upward**, which clears debris quickly and gives the best finish on the **bottom** of the cut:contentReference[oaicite:1]{index=1}. In contrast, a **down-cut** bit pushes chips **downward**, which leaves a cleaner edge on the **top surface** of the material:contentReference[oaicite:2]{index=2}. Essentially, use up-cut bits when you need clean edges on the bottom (e.g. through-cuts or deep slots) and use down-cut bits when you need a splinter-free top surface (like dados or shallow grooves in veneered plywood).

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