Worm shaft ndi gawo lofunikira kwambiri mu bokosi la mphutsi, lomwe ndi mtundu wa gearbox womwe umakhala ndi giya ya nyongolotsi (yomwe imadziwikanso kuti gudumu la nyongolotsi) ndi screw worm. Mtsinje wa nyongolotsi ndi ndodo ya cylindrical yomwe pamakhala zomangira za nyongolotsi. Nthawi zambiri imakhala ndi ulusi wa helical (worm screw) wodulidwa pamwamba pake.
Ma shaft a nyongolotsi nthawi zambiri amapangidwa ndi zinthu monga chitsulo, chitsulo chosapanga dzimbiri, kapena mkuwa, kutengera zomwe zimafunikira pakulimba, kulimba, komanso kukana kuvala. Amapangidwa ndendende kuti awonetsetse kuti akugwira ntchito bwino komanso kufalitsa mphamvu moyenera mkati mwa gearbox.