Mine Roof Double Drill Hole 顶板双位钻孔

double cutting drill 双刃钻

double disc drill colter 双圆盘条播开沟器

double-wall drill pipe 双壁钻杆

double core barrel drill 双筒取心钻具

Double margin drill 领先阶梯钻头

double core-barrel drill 双岩心管钻探

double-core barrel drill [油气] 双岩芯筒钻头

double-disc drill coulter 双圆盘条播开沟器