Bonvario Eurodrives BL series Aluminium Casing Gearboxes are manufactured with high quality material in order to guarantee the maximum reliability and strength for long life of the gearbox. Worm shaft are made of steel which are case hardened to 58-60 HRC and profile ground. The thread grinding in the gear ratios that the module value permits is carried out with ZI- profile. This improves the contact between the toothed surface and therefore performance of the gearbox. This also reduces operating noise of the gearbox. The worm wheel has a G20 cast iron hub onto which a casting in AS 1 bronze RIM is fitted.