From: System 3R hydraulic chuck instructions.
Maintenance and repair.
System 3R hydraulic chucks operate with two parallel
operating pressure chambers. In each chamber a concentric
clamping area is achieved when the locking screw (1) is turning
by a 3R key (2). NOTE: The accessory must be carefully
cleaned before it is inserted in the chuck.
2. Filling with oil:
a) Undo ring nut (3) with hydraulic key (8).
NOTE: Position the chuck so that oil cannot run out.
b) Withdraw cylinder (4) and piston (5). Remove backing ring (6) and 0 ring (7).
c) Fill with oil (Mobil SHC 630 or equivalent).
d) Side 0 ring (black) and backing ring (yellow) on to the piston (5). The 0 ring must be nearest the Oat end of the piston, the text on the backing ring must be facing away from the 0 ring.
e) Slide the piston into cylinder sleeve (4) with the backing ring nearest the sleeve and press in the piston assembly into the chuck until it is stopped. NOTE: Use only hand force.
f) Open the chuck Vent screw about one turn using a 2. mm hex. key.
g) Carefully press in the piston assembly further until the ring nut thread (3) begins to engage. Remove screw (1) and screw the ring nut until it bottoms.
h) Tighten the vent screw immediately using normal hand free
i) Screw in screw (1) until it reaches the piston.