This sintered bronze bushing was not machined properly,
the pores have been smeared over both on
ID and OD. Now you have a cast bronze bearing
- they need to be lubricated. The oil has been sealed
the bearing and the entire purpose
of an filled bushing has been defeated. Oil filled
bushings should be machined by companies that
have extensive experience with this material. No
one has more experience than LM-Tarbell.
This is an
example of proper machining. Please
note the small specs on the body of the bearing.
are evidence that the capillaries from
ID to OD remain open allowing oil to flow
( wick ) readily.
We are often called by engineers who
tell us that oil impregnated bronze bushings failed in
their application. We ask them to send us their failed
bearings and more often than not, they have failed because
they were improperly machined.
Bronze - "A Metallic Sponge"
In order to
properly machine oil impregnated,
bronze bushings an understanding of the manufacturing
techniques of the raw material must
be taken into account.
Sintered bronze begins as powdered metal which is
packed into a die and
pressed under heavy tonnage to
finished blank -
near net - sizes. This material, now in a "green state"
,is then sintered in a furnace to fuse the powdered particles
into a solid form. This form remains approximately 20%
Lubricant is absorbed
and stored in countless thousands of
tiny interconnected pores -
between sintered groups of powder - by vacuum impregnation or
hours long immersion in hot oil. Capillary action holds the
the bearing and
prevents it from dripping out.
As the shaft begins to rotate within the bearing, it
in a boundary situation. At 6 O'Clock, there is
generated to draw oil from thousands
and the shaft
is lifted on an oil film -
process of forming objects from a
metal powder by heating the powder at a
temperature below its melting point.
Through chemical or
mechanical procedures a
powder of the metal
can be produced. When the
powder is compacted
desired shape and
heated, i.e., sintered,
for up to three hours, the
particles composing the
- micro weld - to
form a single densified part.