The piston transmits the
impact energy through
the drill steel to the hole
bottom. A valve directs
the compressed air /
hydraulic oil from one
side to the other of the
piston so that it moves up
Rock drill mechanism
The drill steel is turned lightly with
IN PNUEMATIC ROCK DRILLS :
The rotation is normally anti-clock
wise and normally made on the
return stroke of the piston.
The theoretical angle of rotation per
stroke is 36 degree. In practice it is
30 degree. The difference is due to
IN HYDRAULIC ROCK DRILLS :
Hydraulic motor is normally used for
rotation. The rpm of the drill bit is
adjusted as per drill bit diameter.
Rock drill mechanism
The feed force is created by hand in
case of hand held drills , Pusher leg
or hydraulic cylinder.
Proper feed force will give the best
Improper feed force will cause:
Loosening / damaging of thread.
Overheating / low life of drill string.
Diverted hole / poor pull in blasting.
Rock drill mechanism
Flushing is done
normally by air or
water on all the rock
is used as flushing
flushing will provide
Factors which influence drilling rate
Type of rock
Air pressure/Hydraulic Pressure
Wear of front of rotation chuck
Components of Hydraulic
Drifter Shank Adapter
Hyd. Rotation Motor
Transmit rotation from Hyd.
Motor to Shank Adapter
Triangular in shaped
Housed in rotation chuck
Has internal splines
Made of bronze/Steel
Splines wear limit is half it
Serves as retainer for Shank
Stop Ring is extremely hard
and wear resistant
It is subject to impact
Wear limit is 1 mm to the
front end of the splines
Damping Piston protects the
Rock Drill from shock
waves (thru hydraulic
Subject to powerful axial
It helps in absorbing reflex
shocks upto 20 tonnes.
Since it is pressed against
rot.chuck/shank adapter, it
tends to partially rotate.
Two long side bolts hold
together the external parts of
the Rock Drill (front head,
cover, gear housing, interm.
part and cylinder
Third long side bolts
connect all above parts
except front head.
Two long side bolts have
have integral eccentric
Tension of the side bolts
must be checked
Rear dome nuts are
tightened as per the
change both the bolts
Front and Rear piston
guides located on either end
of the cylinder guides the
lateral movement of the
It prevents the piston lands
from touching the cylinder
Its has wear resistant quality
and also gives lowest
The piston strikes the shank
adapter between 3000 –
3600 stokes per minute
Piston is supported by
Slim piston design transfer
optimum energy to the drill
Slim piston design also has
low stress on Rock Tools
Rotation Chuck Sleeve
Rotation Chuck sleeve
is a press fitted into the
rear of the Rotation
It is made of high
quality bronze with high
resistance to wear and
Rotation Chuck Bushing
The smaller front face of the
Rotation Chuck bushing
acts on the shank adapter.
Larger rear face is subject to
the thrust from the damping
Front face of the rotation
chuck bushing is subject to
Max. permissible wear on
the front face of the rotation
chuck bushing is 1 mm.
Special attention must be paid to safety information
and especially to the warning symbol (triangle).
Never attempt maintenance of Rock Drill when the
hydraulic system is pressurised
Always use correct specification hoses, specially the
impact hose of rating SAE 100 R9R/4SH/4SP (4 layers,
spirally wound steel wire braided).
Use protective plugs when dismantling the Rock Drill
Always overhaul a Rock Drill in a Container or a clean
Before starting up a new or a newly overhauled Rock
Connect up all hydraulic hoses
Charge the Accumulators with Nitrogen gas to the
Fill correct hydraulic and lubricating oil
Adjust correct lubricating system
Tighten all threaded joints after first shift of operation
Check that Air & Lubricating oil come out
between the shank adapter and front guide
Check S/Adapter threads are not damaged
Keep an eye on the hydraulic hose vibration.
If they vibrate too much check the
Check there is no leakage from the Rock
Drill. If flushing water leaks from the hole
in the front head, change the seals.
Every 40 Percussion Hour
Grease the Gear Housing
Tighten all threaded joints as per
Check for external leakage on the Rock
Drill. Replace the seals if leaking
Check condition of hydraulic hoses,
replace damaged/defective hoses.
Every 400 Percussion Hour
Recommended for complete
Overhauling to be done in a clean
and suitable workshop. Always use
Hydraulic Drifter Repair Tools.
Accumulators are fitted with
They should be charged with
Nitrogen gas only (other gas can
All new accumulators are not
Charging the Accumulators
Remove the protective plugs
Open the valve nut and connect the charging hose
Open the gas valve on the cylinder
Charge the Accumulator to the collaring pressure
minus 30 bar. However the maximum pressure
should not exceed 110 bar
Tighten the valve nut and also close the cylinder
Remove the charging hose and fit back the
protective cap on the accumulator valve
30 bar below
Max - 110 bar
Not to be
MAIN COMPONENTS OF DRILL
Transmission Oil & Filter
a. Quality of oil
b. Working temp
Transmission oil change
A - Filling
B - Drain
C - Filter
the oil when it is hot through
drain plug “B”.
e oil through port “A” up to “LOW”
mark on dipstick.
e the filter.
he engine at low idle to fill up the
converter and fill oil up to low mark.
he engine to heat up the oil at 80 deg. C
fill up to high level.
Release Park brake
Loosen lock nut “A”
Screw in stud “B” to
To reset the park
brake screw out the
stud “B” to 47 mm.
Tighten the lock nut.
Service brake adjustment
Place the rig on jacks.
Open the lock nut “A” &
lock plate “B”.
Unscrew the adjusting
screw “C” anticlockwise to
take up any play. Continue
to turn until a torque of 40
Nm is attained.
Now screw the
adjusting screw “C”
clockwise 3 turns.
Refit lock plate “B”
& lock nut “A”.
Drilling is the backbone of all mining & tunneling
applications & thus the role of Electro Hydraulic
Drill Jumbos assumes critical proportions.
While these equipment are quite simple to operate
with built in ling term reliability, optimization of
drilling functions and high levels of availability is
only possible if correct maintenance and
operational directions are followed.
The presenters of this paper thankfully acknowledge the assistance from M/s Atlas
Copco & M/s Sandvik for their inputs during preparation.
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