Grease Replacement; O-Ring Replacement - Hitachi H 90SE Technical Data And Service Manual

7-3. Grease Replacement

Different kinds of grease are used in the electro-pneumatic hammering section and the speed-change gear
section. It is not necessary to replenish the grease between 6-month (approx.) change intervals unless the tool is
disassembled or there is grease leakage due to a damage or worn seal.
To ensure the smooth reciprocating of the striker and the second hammer, special grease (Part No. 980927
for impact drill) is used in the hammering section. If the hammering section [inside the cylinder case and
housing (crank shaft side)] is disassembled, thoroughly wipe away all old grease from all parts, and apply
70 g (2.3 oz) of new grease within the cylinder case and 50 g (1.7 oz) of new grease within the housing
(crank shaft side). Do not exceed the designated amounts of grease. If there is excessive grease, it may
flow between the striker and piston and cause reduced hammering efficiency and/or increased recoil force.
N.P.C. SEP-3A (Part No. 930035) is used in the speed-change gear section (inside the gear cover). The proper
supply amount is 100 g (3.3 oz). Never use the hammering section special grease in the speed-change section.
The special soft grease would leak into the motor section and cause serious problems.

7-4. O-Ring Replacement

The O-ring mounted on the piston is extremely important to ensure adequate sealing of the air pressure. Although
the O-ring is made of special rubber to ensure a long service life, it does nonetheless become worn and should be
replaced periodically depending on the frequency of tool use. With average use, it is recommended that the
O-ring should be replaced every six months to ensure maximum effectiveness.
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