Worm gear and Worm

Worm gear and worm shaft are in the middle of two staggered shafts to transfer the motion and power between the two staggered shafts. The shape of worm is similar to the screw shaft, It will used worm gear if need higher gear ratio, usually the gear reduction of a worm gear is 20:1, or sometimes even up to 300:1 or more.


Generally worm is made with material of carbon steel or alloy steel.

High speed heavy duty worm common used with low carbon steel such as 15Cr, 20Cr, 20CrMnTi and etc, the surface hardness is 56~62HRC after carburizing and quenching.

Medium speed and medium load worm produced with high quality carbon steel material or alloy structure steel such as 45, 45Cr, and surface hardness is 40~55HRC after surface quenching.

Low speed or unimportant transmission, worm can be manufactured with 45 steel and surface hardness is less than 270HBS after QT

Worm gear is manufactured with material of bronze and cast iron. Tin bronze has good wear resistance and glue resistance, but it is more expensive. The common material such as ZCuSn10Pb, CuSn5Pb5Zn5 that used for high speed transmission.

Aluminum-iron bronze has better mechanical property, but its anti~gluing property is worse, common material such as ZCuAI9Fe4Ni4Mn2 is for low speed transmission

Gray cast iron only used for transmission occasion that Vs<=2m./s.

Material for worm and worm gear

Material of Worm:

Material C Si Mn Cr Mo Ni S P Cu
40Cr 0.37~0.44 0.17~0.37 0.5~0.8 0.8~1.1 <=0.1 <=0.3 <=0.03 <=0.03 <=0.03
20CrMnMo 0.17~0.23 0.17~0.37 0.9~1.2 1.1~1.4 0.2~0.3 <=0.03 <=0.035 <=0.035 <=0.03

Material of Worm Wheel:

 Material Cu Sn Zn Pb P AI Mn Si Sb As Ni Fe C
ZCuAl9Mn2 <=0.2 <=1.5 <=0.1 <=0.1 8~10 1.5~2.5 <=0.2 <=0.05 <=0.05
ZCuAl9Fe4Ni4Mn2 <=0.02 8.5~10 0.8~2.5 <=0.15 4~5 4~5 <=0.1
ZCuAl10Fe3 <=0.4 <=0.2 8.5~11 <=1 <=0.2 <=3 2~4
ZCuAl10Fe3Mn2 <=0.5 <=0.3 <=0.01 9~11 1~2 <=0.1 <=0.05 <=0.01 2~4

Worm and Worm gear structure:

Worm structure: worm and worm gear structure

Worm wheel structure:

worm and worm gear structure-1

Installation and maintenance of worm drive:

According to worm drive mesh, the middle plane of worm gear should pass through the axis of worm. Therefore, after worm drive is installed, it needs to adjust the axial position of worm wheel to make its positioning accurate, or it is difficult to mesh properly.

The oil temperature should be tested after the worm drive has been in operation for a period of time. If it exceeds the allowable range of oil temperature, it should be stopped or the heat dissipation condition should be improved. Also check frequently if the worm gear tooth surface remains intact. Lubrication is important to ensure proper operation of the worm drive and extended service life.