Worm gear

Material of the worm gear depends on the slippage speed.

If V_sl>5 m/sec, the worm gear is made of tin bronzes such as Bronze10Sn-1Ni-1P, Bronze10Sn-1P.

If V_sl is ranged from 2 to 5 m/sec, the worm gear is made of tinless (aluminum-iron) bronzes such as Bronze9Al-4Fe.

If V_sl<2 m/sec, the worm gear is produced from cast irons such as Grey cast iron 12 or Grey cast iron 18.

Mechanical characteristics of materials of the worm gear are given in table 6.1. It is recommended to choose the material of the worm gear with higher mechanical characteristics.

It is necessary to note that calculation of the worm gearing is carried out by the material of the worm gear because the latter has less strength in comparison with the material of the worm.

In our case: worm is made of carbon steels of grade Steel 45 (0.45 C) and surface-hardened to hardness ranged from 50 to 55 HRC; the worm gear is made of tinless (aluminum-iron) bronzes such as Bronze 9Al-4Fe with chill casting to s_y = 195 MPa, ultimate strength in tension s_ult = 490 MPa.

Table 6.1