Helical shaper cutters have their teeth inclined at a helix angle to the cutter axis and follow along a helical path. A right hand (RH) helical cutter is described the same way as a RH helical gear; that is, the teeth twist away from the observer in a clockwise direction. Likewise, on a left hand (LH) helical cutter, the teeth twist away from the observer in a counterclockwise direction. A RH cutter produces LH external gears or RH internal gears. A LH cutter produces a RH external gear or a LH internal gear.