Cov txheej no ntawm worm log iav uas tau siv hauv nkoj. Khoom siv 34CrNiMo6 rau cab ncej, kho cua sov: carburization 58-62HRC. Cov khoom siv cab cab CuSn12Pb1 Tin Bronze . Ib lub log iav, tseem hu ua worm iav, yog ib hom iav uas feem ntau siv hauv nkoj. Nws yog tsim los ntawm ib tug cylindrical worm (tseem hu ua ib tug ntsia hlau) thiab ib tug cab log, uas yog ib tug cylindrical iav nrog cov hniav txiav nyob rau hauv ib tug helical qauv. Cov cab iav meshes nrog cov cab, tsim kom muaj kev sib kis zoo thiab ntsiag to ntawm lub zog los ntawm cov khoom siv nkag mus rau lub qhov tso zis.