How to measure Oil Seals

How to measure oil seals

Identifying oil seals can be tricky especially the imperial sizes so here is a little guide that will help you get your job up & running again quickly

Metric Oil Seals

Metric oil seals are more or less straight forward as the size is stamped on the seal for example 20 47 7 this indicates that the inside is 20mm, outside 47mm & width 7mm, some oil seals have different lip arrangements the most common are shown below,

R21 & R23 being the most common R21=Single Lip R23=Double Lip

So for example if you had on your oil seal TC 20 47 7 you would now know that you would need a double lip seal with a 20mm inside, 47mm outside & 7mm width.

Imperial Oil Seals

Imperial oil seals are a little more tricky as the numbers on the oil seal are not in fractions & they always start with the outside diameter first for example 300 212 37 this indicates that the oil seals sizes are 2.1/8" inside, 3" outside & 3/8 wide, below is a table to help you convert these

numbers,

 

1/16

0.06

1/8

0.12

3/16

0.18

1/4

0.25

5/16

0.31

3/8

0.37

7/16

0.43

1/2

0.50

9/16

0.56

5/8

0.62

11/16

0.68

3/4

0.75

13/16

0.81

7/8

0.87

15/16

0.93

1

1.00

 

(Remember the first number is always the outside diameter)

137 62 25 = 5/8" inside 1.3/8" outside 1/4" wide 187 125 25 = 1.1/4" inside 1.7/8" outside 1/4" wide 150 250 37 = 1.1/2" inside 2.1/2" outside 3/8" wide