Abstract
Especially important is the Drill Steel on drilling, I compare with drilling speed on the occasion of next case:
1. Length of steel,
2. Size of steel,
3. Size of bit.
I can announce following by my experiments; it is that by use of sthall steel, if we can, and short bit guage on drilling to the rock drill, drilling speed very increase.
And the shorter steel we use, the better result we have; so avoid long steel.
