HITACHI DH 20DV User guide
MODEL DH 20DV
1. REPAIR GUIDE
Without fail, remove the EB 24B battery from the main body before starting maintenance work. Because the tool is cordless, if the battery is left in and the switch is activated inadvertently, the motor will start rotation unexpectedly, resulting in serious hazard.
1-1. Precautions and Suggestions for Disassembly and Reassembly of the Main Body
The [Bold] numbers in the descriptions below correspond to the item numbers in the Parts List and
exploded assembly diagrams. Front Cap [1]
1-1-1. Disassembly
(1)Disassembly of the chuck section
As shown in Fig. 1, slide the Grip [2] in the direction
Grip [2]
indicated by the arrow mark, and remove the Front Cap
[1]. The Grip [2], the Ball Holder [3] inside the Grip, Holder Spring [4] and two Steel Balls [9] can then be removed from the Cylinder [11].
(2) Disassembly of the housing
After removing the chuck section, loosen and remove the nine D4 x 20 Tapping Screws (Black) [33] and the two D4 x 14 Tapping Screws [32] which fix the main body. Then, separate the Housing (A)(B) Set
[31] by removing Housing (B) from Housing (A).
(3) Disassembly of the hammering mechanism section
When the Cylinder [11] and the Piston [21] are removed from Housing (A) in a single body, the arm of the Reciprocating Bearing [40] will be extracted from the Piston [21]. Then extract the Piston [21] from the Cylinder [11], and with a screwdriver or slender rod push the Second Hammer [16] out through the hole in the tip end of the Cylinder [11] to disconnect the Striker [19] retained by O-Ring (D) [18].
Pull out the First Gear [44] without the bearing from the Second Pinion [36]. Then remove the Collar
[41] and the Reciprocating Bearing [40]. Next, move the Clutch [38] toward the pinion side at the top of the Second Pinion [36], and remove the O-Ring [39]. The Clutch [38] and the Clutch Spring [37] can then be removed from the Second Pinion [36]. Remove the Retaining Ring for D14 Shaft [50] which fixes the Change Lever [46] on the inner side of Housing (A), and extract the Change Lever [46] from Housing (A). Be very careful not to lose the D3.97 Steel Ball [48].
(4) Disassembly of the cylinder and the second gear (slip mechanism section)
Extract the Retaining Ring [5] from the Cylinder [11]. Pull the Oil Seal [6] off of the Cylinder [11]. Extract the Retaining Ring for D20 Shaft [7], and remove the 6904CM Ball Bearing [8] from the Cylinder
[11] with a bearing puller. Be very careful not to lose the four D5.556 Steel Balls [10]. The Second Gear [12], Spring (A) [13] and Washer (A) [14] can then be removed from the Cylinder [11]. Extract O- Ring (D) [18] from deep within the Cylinder [11], and remove the Second Hammer [16] from the Cylinder
[11]. [O-Ring (D) can be easily removed by using the J-201 spring hook (Code No. 970977 is recommended) to pull it out from the outside.] To prevent idle hammering, be sure to replace O-Ring
(D) [18] whenever the unit is disassembled.
--- 1 ---
(5)Disassembly of the switch and the terminal
Remove Housing (B) and pull out the Internal Wires [54] [55] from Brush Holder (L) [59] and (R) [60]. Then the Terminals [66] [68], the Switch [53] and the Internal Wires [54] [55] can be removed together. Perform the following procedure for disassembly of the Terminals [66] [68], the Switch [53] and the Internal Wires [54] [55].
Disconnect the Internal Wires [54] (red) and [55] (black), and the Terminals [66] (brown) and [68] (blue) from the Switch [53] by melting their soldered connections with a soldering iron (350 ˚C, within 5 seconds). Take care not to apply too much heat because it can damage the variable-speed function of the switch. Remove the two D4 Tapping Screws [65] from the Terminals [66] [68].
(6)Removal of the rubber seal
Pull out Rubber Seal (A) [63] gently from the Oil Seal [6] on the housing ass'y. Pull out Rubber Seal (B)
[64] by sliding with your fingers. Take care not to scratch the rubber seals to prevent grease leakage.
(7)Removal of the armature and the magnet
Hook the spring of Brush Holder (L) [59] and Brush Holder (R) [60] on the edge of each Brush Holder. Then remove the Armature [28] and the Magnet [29] together.
(8)Removal of the brash holders
Remove the two D3 Tapping Screws [58] from both sides of Brush Holder (L) [59] and also Brush Holder
(R) [60] (four in total). Then Brush Holders can be removed.
(9)Replacement of the carbon brushes
Remove the Armature [28] and the Magnet [29] together according to the step (7). Pull out each terminal of the Carbon Brushes [57] from the brush holder terminal with a small flat-blade screwdriver, and then remove the Carbon Brushes by pulling them inward. Push each terminal of the new Carbon Brushes in the Brush Holder as far as it will go. Be careful not to contact the spring of the Brush Holder with the wire of the Carbon Brush (pay attention to inserting orientation of the Carbon Brush) or not to hook the spring on the edge of the Brush Holder. Thus, the two Carbon Brushes can be replaced.
1-1-2. Reassembly
Reassembly can be generally be carried out as the reverse of the disassembly procedures, with some items
to be noted as follows:
(1)Be sure to perform wiring connection as indicated in Fig. 2.
(2)Pay attention to the polarity of the Terminal Piece [67], and the Internal Wires [54] and [55] when mounting them to Housing (A). Be careful that the blue and brown Internal Wires cross at the midpoint.
(3)Insert the Armature [28] into the Magnet [29] facing its no-notch side inward. Be careful not to scratch the Armature [28] because the magnet attracts the Armature [28].
(4)Position the Washer [43] between the wall of Housing (A) and the V-ring [42] when mounting the Second Pinion [36] to the main body. Be careful not to position the Washer [43] between the wall of Housing (A) and the First Gear [44].
---2 ---
Loading...