A fly cutter is a cutting tool that mounts one (or more) cutting edges on a tool holder to replace the teeth of a worm gear hob; essentially, it's a single-tooth worm gear hob.
Based on the mounting direction and tooth profile shape of the cutting edges, they are mainly classified into Archimedes worm gear fly cutters, staggered-tooth helical-groove worm gear fly cutters, normal straight-profile worm gear fly cutters, and toroidal worm gear fly cutters. The Archimedes worm gear fly cutter has straight-tooth profiles, with a tooth profile angle equal to the axial tooth profile angle of the basic worm, and its rake face is mounted on the axial plane of the tool holder. The staggered-tooth helical-groove worm gear fly cutter uses a staggered-tooth helical-groove structure, with positive working rake angles on both sides, improving the sudden change in impact load and enhancing cutting stability. The normal straight-profile worm gear fly cutter refers to a cutter whose straight-profile tooth rake face is mounted in the normal plane of the basic worm, suitable for machining ZN-type worm gears. The toroidal worm gear fly cutter is a simplified cutting tool for toroidal worm gears, with various structural forms, including double-tooth fly cutters and multi-tooth fly cutters, among which multi-tooth fly cutters offer higher machining accuracy but have a more complex structure.
A pull-pin type tool holder structure not only stably fixes the fly cutter's cutting edge to the tool holder, but also allows adjustment of the fly cutter's tilt angle.
The main processing equipment is a gear hobbing machine with a tangential tool holder. During gear cutting, in addition to the hobbing rotation of the fly cutter and the workpiece, the fly cutter also performs a tangential feed motion to continuously generate the tooth profile. Worm gears can also be machined on a milling machine using a fly cutter, but the machining accuracy is lower.
