Hitachi DH 40SR Service Manual And Technical Data page 18

Slip clutch mechanism
The slip clutch mechanism is described below with reference to Fig. 6. The bevel pinion and the gear holder
are coupled together by the key and press-fitting. Spring (C) and needle pins are housed in elongated
grooves of the gear holder. The needle pin is pressed against the inner face of second gear by spring (C) to
allow idle rotation of the second gear relative to the gear holder. When an excess torque is exerted on the
bevel pinion shaft, the needle pin is raised upon the projection of the second gear against the load of spring
(C) to allow idle rotation of the second gear. With the arrangement, the clutch slips when an excessive torque
is applied to the working tool as when the drill bit contacts steel bar/wire in the concrete, protecting the
operator from unexpected motion of the side handle.
Bevel pinion
Gear holder
Tool holder
Pushing button
Retainer
Front cover
Fig. 7
Handle and side handle
The handle section is of a two-layer structure. The base is made of glassfiber-reinforced plastic and the
outside layer is soft resin. They are molded in one piece.
The side handle also has a two-layer structure. The base is made of glassfiber-reinforced plastic base with a
steel nut and the outside layer is soft resin. They are molded in one piece. The newly designed handle and
side handle structure ensures more comfortable grip for improved operability.
Second gear
Bevel pinion
Gear holder groove
Fig. 6
The Model DH 40SR is equipped with an easy pushbutton-
type tool holder. To attach a tool, pull up the retainer in the
arrow direction and insert a tool into the hexagonal hole of the
front cover then pull down the retainer (Fig. 7).
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Needle pin
Gear holder
Cross section A - A
Spring (C)
Key