... to prevent premature wear of the matrix. Surface-Set diamond bits are primarily recommended for use in drilling relatively soft, abrasive ... , unconsolidated formations that are not effectively drilled by impregnated diamond bits. They are also recommended for use in drilling harder formations ... ,BTW,NTW,NXD3,AX,NX,NXC,AXT,T6H,4 9/16,NWD4,412F,SK6L146,TT46,TB56,TS116,CHD10 API Surface-Set ...