Kuthamanga kwapakati ndi kutsika kwamphepo kwa DTH bits
Ubwino waHFDkubowola pansi pamadzi
Chobowolacho chimapangidwa ndi zinthu za alloy, zomwe zimakhala ndi moyo wautali wautumiki ndipo zimakhala zapamwamba kuposa zinthu zofanana, ndipo kubowola kumaphwanya mwala ndi kumeta ubweya. Mabowo a HFD ali ndi mphamvu zobowola mwamphamvu ndipo ndi oyenera kubowola mofewa ndi molimba (kubowola kwa giredi 9 pa rock, hard rock drilling), poyerekezera ndi pang’ono, makamaka pobowola miyala ya giredi 6-8 zotsatira zake zimakhala zofunika kwambiri.
