Carbon materials for bearings
Generalities
Bearings are made of impregnated or not
impregnated carbon materials.
They are working generally in dry or mixed friction conditions.
Mixed friction appears when bearings work in fluids with low
hydrodynamic lubricating properties.
Bearings are produced according to customers' designs.
Radial Bearings with Smooth Bores
They are used for dry running conditions. Machining
is made in IT 7, IT 8 tolerance class, having the roughness of the
bore Ra = 1 mm.
Radial Bearings with Lubricating Grooves
Sometimes for wet running are used bearings with lubricating
grooves in the bore.
They can have spiral or axial form.
Axial
Bearings
The axial bearings generally have facial
grooves which help to establish a lubricating film between
the bearing faces.
Note
Because of their lower strength
and of their brittleness compared with metals,
bearings of carbon materials are usually fitted by pressing or shrinking
in metal holders.
For the bearing play design it is necessary
to specify that, because of the shrinking
stress up to the shrinkage temperature, the bore
of the bearing expands with a coefficient of thermal expansion
close to the holders' one.
For shaft material is recommended one as hard as possible.