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Cylinder Tube Material
Use cylinder tube materials specified by industrial standards for hydraulic cylinders. Aluminum alloy, bronze, brass, monel metal and soft stainless teel may be used for low-pressure applications depending on circumstances. But they are not recommended for use for a long period because of poor wear resistance.
Inside Face Cylinder
Generally a honed finish is recommended for the inside face of the cylinder tube.
1.6S rod with buff finish, after heat treatment plating the steel with hard chrome is recommended for rod surface. Never use decorative nickel plating or chrome plating. The cylinder rod used for construction machinery is likely to be scored by sands or pebbles, so minimum hardness should be 60 (H(R)C).
Bearing Clearance and Extrusion Gap
Since bearing clearance and extrusion gap greatly affect the packing performance, make them as small as possible. (See diagram below for bearing clearance and extrusion gap). Never use a packing in place of bearing.
Roughness of Inside Face of Fitting Groove
Since a rough inside face of the fitting groove affects the sealing of a packing, surface finish of 3.2S us recommended. In fitting the packing, it is easily scratched, so finish the edge of the groove completely removing any burrs, sharp edges and scars.
Design of Packing Insertion Port
There is an “interference” on the I.D. and O.D. of the packing to achieve sealing performance. When installing a packing in a cylinder, the lip of the packing, its most important part, is easily damaged, if the size and construction of the chamfered edge of the insertion port are poor. Especially watch for the design of any threaded part as shown in Figure D-C2.