Precautions In Disassembly And Reassembly; Disassembly - Hitachi DH 20PB Technical Data And Service Manual

9. PRECAUTIONS IN DISASSEMBLY AND REASSEMBLY

The [Bold] numbers in the descriptions below correspond to the item numbers in the Parts List and exploded
assembly diagram.

9-1. Disassembly

(1) Disassembly of the Striking Mechanism Section
With a drill bit or screwdriver bit, push in the Second Hammer [25] to release the Striker [28] from the O-Ring
(I.D.10.5) [27].
Set the Change Lever [13] to a position halfway between the "Drill" and "Hammer" marks on the Gear Cover
[7], insert a small flat-blade screwdriver into the concave position located on the rear end of the Change Lever
[13], and pull it off. (It is very important to ensure that the Change Lever [13] is positioned halfway between
the "Drill" and "Hammer" marks when it is disassembled or assembled.)
Loosen the four Tapping Screws (W/Flange) D5 x 35 [8], and remove the Gear Cover [7]. The Inner Cover
[33] and the Housing [53] are loosely fitted together. Attempting to pull them out first could cause the
Armature [46] to be pulled out at the same time, causing damage to the Carbon Brushes [62].
Remove Spring (B) [34] from the end of the Gear Shaft Set [35], and turn the Gear Shaft Set [35] so that the
Piston [30] moves to its maximum upper position (inner cover side). The arm of the Reciprocating Bearing
[40] can then be disconnected from the Piston Pin [31], and the Gear Shaft Set [35] and the components
mounted on it can be removed from the Inner Cover [33] as a unit.
With a bearing puller (Special Repair Tool J-30 Bearing Puller Ass'y, Code No. 970804, is recommended),
remove the Spacer [41] from the Gear Shaft Set [35]. Then take off the Reciprocating Bearing [40]. At this
time, carefully note that the Spacer [41] must be aligned with and press-fitted onto the 9 mm diameter end of
the Gear Shaft Set [35].
Move the Clutch [38] to the pinion side of the Gear Shaft Set [35], and pull off the O-Ring (S-8) [39].
The Clutch Spring [37] and Washer (B) [36] can then be removed from the Gear Shaft Set [35].
(2) Disassembly of the chuck section
As shown in Fig. 8, slide the Grip [2] in the direction
indicated by the arrow mark, and remove the Front Cap
[1]. The Grip [2], the Ball Holder [3] inside the grip, the
Holder Spring [4], Washer (B) [5] and the Steel Ball D7.0
[18] can then be removed from the Cylinder [20].
Fig. 8
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Front Cap [1]
Grip [2]