Changeover Between "Rotation Only" And "Rotation And Hammering - Hitachi DH 14DL Technical Data And Service Manual
14.4/18 v cordless rotary hammer
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Also See for DH 14DL:
- Handling instructions manual (108 pages) ,
- Handling instructions manual (28 pages) ,
- Handling instructions manual (66 pages)
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Hammering function
The piston reciprocates within the cylinder to move the striker in the same manner as in conventional
hammer drills. As the piston reciprocates, the changing air pressure inside the air chamber between the
piston and the striker causes the striker to move and continuously strike against the end of the second
hammer. At the same time, the changing air pressure within the air chamber which moves the striker
also provides an "air cushion" which absorbs the impact of the hammering action. As any air leakage
from the air chamber would weaken the air-cushion effect and reduce impact absorption, the O-ring
(mounted on the striker) is extremely important to seal the air. Although special rubber material is
utilized in construction of the O-ring to make its effective service life as long as possible, wear cannot be
fully avoided. Accordingly, it is recommended that the O-ring be replaced approximately once a year,
depending on the frequency of usage of the tool.
Slip mechanism
The slip mechanism in the Models DH 14DL, DH 14DMR, DH 18DL and DH 18DMR consists of a coil
spring which applies a pre-set amount of pressure to ensure the interlocking of three claws provided on
the flange of the cylinder (the final rotating shaft) and three matching claws provided on the face of the
second gear, by which rotation is transmitted to the cylinder. The second gear is fitted to the cylinder
with a certain amount of play. If an excessively large torque is applied to the tool shaft (cylinder), the
force of the torque will exceed the pressure of the coil spring and cause the claws on the second gear to
disengage from and ride over the claws on the cylinder so that the second gear idles and does not
transmit rotation. Even should the drill bit come in contact with a reinforcing bar within the concrete,
causing sudden excessive torque, the slip mechanism functions to prevent damage to the gears, and
possible loss of control of the tool by the operator. The slip torque applied onto the tool shaft is set to 1.7
to 2.2 kgm.
Sealed and dustproof construction
The gear cover is totally enclosed by oil seals, O-rings and other devices to prevent leakage of
lubricating grease, and to keep dust and dirt out of the internal mechanisms. The drill bit chuck portion is
protected by the rubber front cap to keep out dust and chips which could cause improper fitting of the
drill bit and/or other faulty operation of the chuck portion. The speed control switch is also a fully dust-
proofed type to prevent dust and chips from entering the handle section and causing possible
operational trouble or a breakdown of the insulation.
Speed control
Each of the Models DH 14DL, DH 14DMR, DH 18DL and DH 18DMR is equipped with a variable speed
control switch which permits free change of the rotation speed and striking force. When drilling in fragile
materials, pull the switch trigger gently for low rotation speed (striking force) to achieve optimum results.
In the reverse rotation mode, the operator can pull the switch trigger only halfway and the rotation speed
is decreased to about half of the speed in the forward rotation mode. In addition, the switch stopper
cannot be used in the reverse mode.
3. Changeover between "Rotation only" and "Rotation and hammering"
The change lever of the Models DH 14DL, DH 14DMR, DH 18DL and DH 18DMR permits easy changeover
between the "rotation only" and "rotation and hammering" functions. Set the change lever to "rotation and
hammering" (
marks). Press the drill bit against the workpiece and pull the switch trigger. Then the
armature starts rotating, and the rotation and the striking force are transmitted to the drill bit by the
mechanism as described in page 14 "Piston reciprocating mechanism." After drilling, take the drill bit
away from the workpiece. Then the rotation of the reciprocating bearing and the hammering operation
are stopped by the idle striking prevention mechanism as described in page 2. Set the change lever to
"rotation only" (
mark). The stopper of the change lever contacts the rear surface of the thrust plate
that is pushed forward by spring (B). Thus the cylinder cannot go back even if the main body is pressed,
and the claws on the clutch cannot engage the matching claws on the reciprocating bearing. The
reciprocating bearing idles on the second shaft and only the rotation is transmitted to the drill bit.
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