An zaɓi daidaitattun ƙwallon ƙwallon ƙwallon ƙafa tare da abun ciki na carbon da chromium kuma an ɗaure su don jure matsananciyar matsa lamba tsakanin abin birgima da zoben ɗagawa.
Carbonitriding akan zoben ciki da na waje shine ainihin tsari na taurare don yawancin masu samar da ƙwallon ƙwallon TPI. Ta hanyar wannan magani mai zafi na musamman, taurin kan filin tsere yana ƙaruwa; wanda ke rage lalacewa daidai.
Ƙarfe mai tsaftar tsafta yana samuwa a cikin wasu nau'ikan samfurin ƙwallon ƙafa na TPI a yanzu, ana samun juriya mafi girma yadda ya kamata. Tunda gajiyawar hulɗa galibi ana haifar da shi ta hanyar haɗaɗɗun da ba na ƙarfe ba, bearings a zamanin yau yana buƙatar matakan tsafta na musamman.