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Housing Diametral Tolerances
The following tolerances are as specified in ISO/R266, ISO Systems
for limits and fits - Part 1.
| Cylinder bore diameter |
d3 |
H8 |
Piston rod housing diameter |
d7 |
H8 |
| Piston diameter |
d4 |
f7 |
Axial housing - outside diameter |
d9 |
H11 |
| Piston rod diameter |
d6 |
f7 |
Axial housing - inside diameter |
d10 |
h11 |
It is possible to relax these tolerances depending
upon the application and providing the gland depth gd is kept. It
should be noted that radial clearances should be kept to a minimum
where higher pressures are encountered, to guard against extrusion
of the O-Ring.
Surface Finish
For static seals the surface finish is not too critical. However,
a maximum of 0.8µm Ra (32µin CLA) is recommended for
the housing sides and the static diameter. For the mating surface
in contact with the O-Ring (cylinder bore or piston rod), a maximum
of 0.4µm Ra (16µin CLA) is recommended. A finish of
less than 0.2µm Ra (8µin CLA) is not recommended since
such a finish may be wiped dry as the rod piston extends, leaving
insufficient lubrication for the return stroke.
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