To be used only on CNC machines and routers with automatic feeding. Produce super clean, smooth cuts especially in acrylic materials (Plexiglas Lucite) other plastics and wood. Bits are made according to strict tolerances from an exclusive carbide grade and polished to a mirror finish using amana's unique process. Designed to eject chips up. Ideal for industrial applications and CNC machines. Left hand helix left hand cut., #51504, direction down-cut, (D) diameter 1/4, (b) Cutting height 3/4, (D) shank 1/4, overall length (L) 2, flutes 1, 51504 Solid Carbide CNC spiral 'o' Flute, plastic cutting 1/4 dia x 3/4 x 1/4 inch Shank down-cut