https://www.rockler.com/onsrud-down-cut-spiral-bits
Onsrud Down-Cut Spiral Router Bit's down-shear spiral action prevents chip-out and fuzzing at the edge of the cut - ideal for cutting clean dados, grooves and...
spiral router bitscutwoodworkinghardware
https://www.rockler.com/freud-down-spiral-router-bits
Freud Down-Spiral Router Bit's downward spiral leaves clean, splinter-free edges for dados, grooves and rabbets
spiral router bitsfreudshankwoodworking