With the development of machines, tools and other integrated technologies, from the 1980s, domestic and foreign enterprises have gradually adopted as scraping hardened hardened gear (40 ~ 65hrc) of semi-intensive, finishing methods. This method can process any helix angle, modulus 1 ~ 40mm gear. Ordinary precision (6 to 7) hardened gear, generally use the "roll - Heat treatment - scraping" technology, roughing and finishing can be completed on the same hobbing; tooth surface roughness higher gear, you can scrape after honing processing arrangements; for high-precision gears, the use of "rolling - heat treatment - scraping - milling" process, used for semi-finishing operations scraping replace kibble, removal of heat deformation gear, leaving small and uniform margin conduct grinding, grinding work can save 1 / 2-5 / 6, very significant economic benefits. For hardened gear modulus big, large diameter, large width, because there was no corresponding large grinding machine, generally only use scraping process.