damaged or the gas pressure has dropped
abnormally due to a gas leakage.
Pay attention to the yawing of the drill
mounting. Violent yawing of the drill mounting
is caused by improper feed pressure. Adjust the
feed force by using the feed pressure adjusting
NOTE: Improper feed pressure shortens the life of
the feed chain, the rod, the sleeve, and the shank. It also
results in poor penetration rates.
ADDING EXTENSION RODS. Components of
the rock drill, used when adding or removing extension
rods, are shown in figure 14-26.
Adding extension rods, commonly called drill steel,
is performed as follows:
1. Feed the drifter down and hold the coupling on
top of the centralizer. Engage the drifter hammer until
the coupling is loose.
2. Reverse rotate and allow the drifter to back out
of the coupling, then run the drifter to the top of the drill
guide. Be sure to grease the drifter shank or tamper bar,
and ensure the coupling remains on the drill steel down
in the borehole.
3. Attach another coupling to the drifter shank or
tamper bar. Add additional drill steel; forward rotate
until all is coupled.
4. Lift the coupling off the centralizer. Then open
the centralizer and continue drilling until the coupling
has completely passed the centralizer. Once the
coupling has passed, close the centralizer around the
REMOVING EXTENSION RODS. Once the
rock drill has reached the desired depth, removing the
extension rods is performed as follows:
1. Clean the hole completely before removing the
2. Move the rotation control lever to the neutral
position to stop rotation.
3. Place the coupling on top of the centralizer, and
allow the drill to hammer on the shank to loosen the
4. Shut off the drill.
5. Reverse rotate the steel from the coupling.
Figure 14-26.-Components of the drill guide.
NOTE: Keep an eye on the coupling that connects
the drill shank to the drill steel. This coupling will work
loose faster than the lower coupling and could fall.
6. Run the drifter down to the coupling that is
resting on the centralizer.
7. Forward rotate the drifter into the coupling.
8. Run the drifter with the attached coupling and
drill steel to the top of the drill guide. To remove