Also known as O-flute bits, the flutes on these bits are open and rounded for efficient chip removal when cutting aluminum. This also reduces heat to prevent melting or warping. Use these bits to create square slots, pockets, and edges. They are plunge cutting, letting you cut directly into the workpiece from above. They do not have a pilot, so guide your router along a straight edge when hand routing to make accurate cuts.

Carbide bits have a longer life and faster cutting speeds than high-speed steel bits. Their extreme hardness makes them brittle, so they’re not recommended for use with hand tools. A highly rigid setup, such as a CNC machine, is necessary to keep bits from breaking. Zirconium-nitride (ZrN) coated carbide bits have a smoother cutting edge than uncoated bits, so they generate less friction when cutting. This helps keep temperatures down when cutting at high speeds, minimizing material buildup and extending the life of the bit.

Bits with spiral flutes leave a smoother finish than straight-flute bits and make plunge cuts more easily. Bits with upward chip removal lift chips up for applications that require a smooth finish on the bottom edge of the cut. Securely clamp the workpiece before routing to prevent lifting.

Choose a bit with one flute for a faster cut; bits with two flutes produce a smoother finish.