Hitachi DH 40SR Service Manual And Technical Data page 19

Sealing and dust-proof structure
The cylinder crank case section is tightly sealed with three o-rings, three oil seals and rubber seal as shown in
Fig. 8. This prevents leakage of grease from the cases, while also protecting them against dust from outside.
The tool holder is also protected from foreign dust by means of a rubber dust cover.
O-ring
Rubber seal Oil seal
O-ring
Dust cover
O-ring
Oil seal
Oil seal
Fig. 8
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