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