How To Measure both Imperial and Metric Oil Seals Correctly

By Dichtomatik on 10 March 18 Blog

Dichtomatik Americas has a wide range of services and expertise to offer in the field of sealing solutions, but sometimes it is still useful to know how to do things for oneself.  One excellent example of this is the measurement of oil seals.  Both standard and metric oil seals use similar measuring systems, but they are unintuitive.  In this blog, we wanted to quickly cover the differences in measurement systems and provide a general guide to the measurements for any type of oil seal.

Understanding the Measurement Systems of Imperial and Metric Oil Seals

  1. Metric

Metric seals are by far the easier to measure, because most of the time, the size of the seal will already be stamped somewhere on its exterior.  The numbers lack measurement units but can be quickly identified once someone knows the format.

The standard format is Inner size, Outer size, Width, all measured in millimeters.  So, for example, a metric oil seal stamped with 25 45 5 has an inner ring size of 25mm, an outer measurement of 45mm, and a width of 5mm.  This number may also be preceded by the letters SC or TC, which indicate the lip arrangement.  SC is a single lip, TC is a double lip.

  1. Standard\Imperial

Measuring oil seals with Imperial units is trickier, even though they also have measurements stamped on the outside.  However, unlike metric seals, the format for the Imperial numbers is Outer, Inner, and Width.  This is an important distinction to remember, and one which has tripped up plenty of engineers over the years!

Adding to the difficulty is that the numbers represent fractions, but expressed as decimals.  So a seal with measurements of 1.7/8″ outside, 1.1/4″ inside, and 1/4″ width would be written as 187 125 25.   Likewise, 300 212 37 would translate to 3″ outside, 2.1/8″ inside, and 3/8″ width.

A fraction-to-decimal chart will be of great help in converting these measurements.

Dichtomatik Americas Are Your Oil Seal Experts

Whether you need a custom-engineered solution for a truly unique sealing challenge, or simply want to double-check your math when converting Imperial oil seal measures, Dichtomatik Americas is here for you.  Contact us today with your questions or engineering problems!