Size calculations                    Imperial size calculations
These are standard metric calculations for Vesconite in industrial and pump applications. When considering marine rudder and stern tube bearings, unique marine equations need to be used.

Press fits / interference fits Bore closure Assembly clearance High temperature calculations Low temperature calculations Calculation of the bearing size Final machining of a bearing after installation Temperature limits Machining tolerances

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 5° to 70°C.
Bearings with an interference fit are installed by pressing or freezing.
The interference fit / press fit is calculated as:

Press fit = 0.05 mm + (0.002 x housing diameter)

Press fit = 0.002" + (0.002 x housing diameter)

For temperatures below 5°C use low temperature equations.
For temperatures above 50°C use high temperatures equations.

Bore closure
The closing of the Inside diameter when a bearing is pressed into a housing is called the bore closure.

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.

Assembly clearance = 0.05 mm + (0.02 x wall thickness)
Assembly clearance = 0.002" + (0.02 x wall thickness)

High temperature calculations
Temperatures from 50° to 70°C
Add and extra clearance to allow for thermal expansion of the bearing and avoid seizure on the shaft at the high temperatures.

For temperatures higher than 70°C 
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 = 0.1 mm + (housing diameter x 3.14 x (Tmax-25) x 0.00006)
Press fit=0.

Low temperature calculations
When temperatures are below 5°C, 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 = (5-Tmin) x 0.000054 x (housing diameter) mm
Total press fit = standard press fit + additional press fit.

Additional press fit = (77-Tmin) * 0.00003 * (housing diameter) 
Total press fit = standard press fit + additional press fit.

Calculation of the bearing size
When the bearing is machined before installation, calculate the sizes as follows:

Outside diameter = housing diameter + total press fit
Inside diameter = shaft diameter + assembly clearance + bore closure + extra clearance

Outside diameter = housing diameter + total press fit
Inside diameter after installation = shaft diameter + assembly clearance + 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
OD = housing + PF
Inside diameter after installation = shaft diameter + assembly clearance + extra clearance

Outside diameter = housing diameter + total press fit
Inside diameter after installation = shaft diameter + assembly clearance + extra clearance

Temperature limits
Vesconite can operate safely up to 120°C in dry conditions and in wet conditions up to 65°C and to below -40°C.
If the operational temperature for your application is higher than 65°C (150°F) or below -20°C (-5°F) technical solutions are available such as high temperature materials such as HiTemp 150. Please contact VescoPlastics for further information.

Where the application has a temperature higher than 50°C or lower than 5°C, additional size considerations are made. Please refer to the metric size calculations for high  and low temperatures.

Machining tolerances 

Machining guidelines for Vesconite
Bearing groove design