PDC bits have been used to drill the homogeneous formation from soft to medium-hard, but they are not suitable for drilling in gravel and multi-interbedded formation.

PD C钻头用于软到中硬的均质地层钻进具有钻速高、寿命长等特点，但不适合含砾石地层和软硬交错地层。

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The medium favors hard 90-degree angles, but that shouldn't stop us from including diagonals, zig-zags, and squiggly lines in our designs.

媒体偏爱实线90度角，但那不应当阻止我们在设计中加入斜线、锯齿线和波浪线。

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Medium hard formation with high compressive strength. Such as hard shale, limestone, sandstone, dolomite, anhydrite and marble.

高抗压强度的中硬地层，如硬页岩。石灰岩。砂岩。白云岩。和硬石膏。大理石。

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When times improve, small and medium-scale manufacturers will find it hard to restart without access to Chinese money.

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