DHD DTH rauj
HFD's DTH Hammer yog tsim los siv cov txheej txheem kev tsim khoom zoo tshaj plaws los xyuas kom meej qhov zoo tshaj plaws ntawm qhov siab dua drilling ceev thaum muab Kev Txhim Kho hardness kom nthuav dav lub neej ntawm rauj thiab txo nws txoj kev siv.
Qhov zoo tshaj plaws rau kev xav tau qhov chaw drilling.
