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vesconite.com > Design technical information > Imperial size calculations |
Imperial
size calculations Metric
calculations
These
are standard imperial calculations for Vesconite in industrial and
pump applications. When considering marine applications, unique
marine equations
need
to be used.
Press
fits / interference fits
This is
the most common method for securing a Vesconite bearing. Usually
suitably to secure a bearing under standard environmental operating
temperatures from 23° to 158°F.
Bearings
with an interference fit are installed by pressing
or freezing.
The
interference fit / press fit is calculated as:
Press
fit = 0.002" + (0.002 x housing diameter)
For
temperatures below 41°F, use
low temperature equations.
For
temperatures above 122°F, use high
temperature equations.
Bore
closure
The
closing of the Inside diameter when a bearing is pressed into a
housing is called the bore closure.
|
Bore closure = |
total press fit x housing diameter |
| shaft diameter |
Assembly
Clearance
This
is the gap between the bearing inside diameter and the shaft after
installation. An assembly clearance is needed to allow free movement
of the shaft across its standard operating temperature
range.
High
temperature calculations:
Temperatures
from 122° to 158°F
Add and
extra clearance to allow for thermal expansion of the bearing and
avoid seizure on the shaft at the high temperatures.
|
Extra clearance= |
[(housing diameter)²-(shaft diameter)²] * (Tmax-122)*0.000033" |
|
shaft diameter |
For
temperatures higher than 158°F
It is
not possible to use an interference fit as the resulting strain and
loss of elasticity at elevated temperatures can result in bearings
becoming loose at ambient temperatures. The bearing needs to have an
expansion gap and needs to be mechanically
secured.
The size
of the expansion gap is calculated as:
|
Expansion gap = |
0.005" + (housing diameter x 3.14 x (Tmax-77) x 0.000033) |
| Press fit=0 |
Low
temperature calculations
When
temperatures are below 41°F, additional press fits are required
to ensure that the bearing remains secure at the low temperatures.
The
additional press fit is calculated as:
Additional press fit = (77-Tmin) * 0.00003 * (housing diameter)
Total
press fit = standard press fit + additional press fit.
Calculation
of the bearing size
Outside
diameter = housing diameter + total press fit
Inside
diameter = shaft diameter + assembly clearance + bore closure + extra
clearance
Final
machining of a bearing after installation
In some
cases it is required to first install the bearing and then machine
the inside diameter. In the case of an oval housing or when line
boring is required, this might be required.
Outside
diameter = housing diameter + total press fit
Inside
diameter after installation = shaft diameter + assembly clearance +
extra clearance
Temperature
limits
While
Vesconite can operate safely up to 250°F in dry conditions and in
wet conditions up to 160°F. Temperatures below -40°F are
regarded as low.
If the
operational temperature for your application is higher than 150°F
or below 5°F technical solutions are available such as high
temperature materials like HiTemp 150. Please contact VescoPlastics
for further information.
Where the application has a temperature higher than 122°F or lower than 41°C, additional size considerations are made. Please refer to the Vesconite size calculations for high and low temperatures.
Machining
tolerances
Machining
guidelines for Vesconite
Bearing groove
design
Updated Jun 02 2005
