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Size calculations for marine applications
These are standard marine calculations for Vesconite. Vesconite is also suited to industrial and pump applications. Unique metric and imperial calculations are used for these applications.

Press fits / interference fits
Bore closure
Assembly clearance for rudder and stern tube bearings
Bearing sizes
Grooves for marine bearings

 

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 (23° to 158°F)
Bearings with an interference fit are installed by press or freezing fitting.
The interference fit / press fit is calculated as:
For minimum operating temperature > -5°C
Press fit = 0.05 mm + (0.002 x housing diameter)
Press fit = 0.002" + (0.002 x housing diameter)


For minimum operating temperature <-10°C
Press fit = 0.05 mm + (0.0034 x housing diameter)
Press fit = 0.002" + (0.0034 x housing diameter)

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

Bore closure = 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.

For rudder bearings
Assembly clearance = 0.2 mm + 0.0015 x (shaft diameter)
Assembly clearance = 0.008" + 0.0015 x (shaft diameter)

For stern tube bearings
Assembly clearance = 0.2 mm + 0.002 x (shaft diameter)
Assembly clearance = 0.008" + 0.002 x (shaft diameter)

Calculation of the bearing size
Outside diameter = housing diameter + press fit
Inside diameter = shaft diameter + assembly clearance + bore closure

Machining tolerances
Vesconite bearings machine easily on standard metalworking or wood working equipment.
The following tolerances are suited to most general purpose applications.

Outside diameter

OD tolerance

± 0.1% outside diameter

Minimum

± 0.025 mm

0.001"

Inside diameter

ID tolerance

± 0.1% inside diameter

Minimum

± 0.025 mm

0.001"

Wall thickness

Wall thickness tol

+ 0.0 / -0.5% wall thickness

Minimum

+ 0.0 / -0.025 mm

+ 0.0 / -0.001"

Length

Length tolerance

+ 0.0 / -0.5% length

Minimum

+ 0.0 / -0.3 mm

+ 0.0 / -0.01"


Grooves for marine bearings
Generally Vesconite rudder bearings do not need to water circulation grooves.
Vesconite stern tube bearings should be grooved as follows.

Shaft diameter

No. of grooves

Groove width

Groove depth

mm

Inches

mm

Inches

mm

inches

60-79

2-3

7

7

0.25

4

0.15

80-119

3-5

7

9

0.3

5

0.2

120-159

5-6

7

10

0.35

6

0.25

160-199

6-8

7

12

0.4

7

0.3

200-249

8-10

7

12

0.4

8

0.3

250-299

10-12

7

14

0.5

8

0.3

300-349

12-14

8

15

0.5

8

0.3

350-399

14-16

8

15

0.5

8

0.3

400-499

16-20

9

15

0.5

9

0.35

500-599

20-24

10

18

0.5

9

0.35

600-699

24-28

11

18

0.5

9

0.35

700-800

28-32

12

18

0.5

9

0.35


Machining guidelines for large Vesconite bearings

Updated  Jun 21 2005

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