Mbiri Yachidule Ya Owomba

	Zida za tchisel kale zimadziwika kuti "zida zogawanika" ndipo zidagwiritsidwa ntchito kwa zaka makumi ambiri ndi omanga kupanga kumaliza njerwa (m'mphepete mwake) zitadulidwa ndi njerwa. Tong (mu nyundo kapena chisel version) idzagwiritsidwa ntchito kuchotsa mbali zonse zotsalira.
	Mwachikhalidwe, ratchet / tepi wakhala ratchet, pamene ratchet ndi kupangidwa posachedwapa. Komabe, onsewa tsopano amagawidwa ngati zida zodula. Dzina la nyundo ya trephine linasintha kuchoka ku scotch tepi kupita ku ratchet kumayambiriro kwa zaka za m'ma 20 pamene chidacho chinasinthidwa kukhala cholimba kwambiri. M'mbuyomu, tepi ya Scotch inali ndi katundu, tsamba ndi wedge. Poyerekeza, chida chamasiku ano "chokonzeka" chocheka (nyundo kapena chisel) sichimagwiridwa pamodzi ndi mphero yolimba.
	Kuyambira chapakati pa zaka za m’ma 19, omanga miyala anayamba kugwiritsa ntchito chida chodula m’malo mwa nkhwangwa kuti amalize njerwa. Izi zinali choncho chifukwa chodulacho sichinkafunika kunoleredwa nthawi zambiri chifukwa cha mutu wake wosinthana, komanso chinkatha kudula njerwa zolimba kuposa nkhwangwa yomerera njerwa. Nkhwangwa za njerwa siziyenera kugwiritsidwa ntchito, mwachitsanzo, pamakoma amiyala owuma, pomwe ma rattles amatha.
	Chida chocheka ndi choyenera pa ntchitoyi kusiyana ndi nkhwangwa ya njerwa chifukwa chimakhala ndi m'mphepete mwake (zisa kapena zoyendetsa), kutanthauza kuti simuyenera kuchinola nthawi zonse kapena kugula chida chatsopano, odula okha. Komano nkhwangwa ya njerwa imafunika kuwongoleredwa nthawi zonse podula njerwa zolimba.
	Njerwa zolimba ndi njerwa zomwe zawotchedwa pakati pa ng'anjo (popanga njerwa), zomwe zimapangitsa kuti zikhale zolimba komanso zolimba kuposa njerwa zofewa (njerwa zomwe zingagwiritsidwe ntchito ngati makoma amkati chifukwa cha kusowa kwa moto). kuphika).