短语词组短语metric plum grub screw 公制无头梅花螺丝hollow grub screw 平头空心螺钉conical pointed grub screw 锥形沉头螺钉;锥端无头螺钉hexagon socket grub screw 六角凹头无头螺钉grub screw thread 无头螺钉螺纹lock grub screw 锁紧螺丝 返回 grub screw