Oil Seal Overview
Oil seals, often called a rotary shaft seal or grease seal, closes the gap between stationary and moving components in mechanical equipment — most often rotating shafts — helping prevent lubricant escape and stopping harmful materials, such as dirt, from moving in through the clearance. Oil seals are most commonly used in gearboxes, hydraulic cylinders, and related components.SHOP FOR OIL SEALS
Oil Seal Part Number System
Global O-Ring and Seal’s oil seal part numbers are designed to describe the seal size, style, and material composition. When searching for oil seals via our online store, you will not only be presented with your selection but with comparable oil seals of the same dimensions. There are often viable style substitutions which are functionally compatible, but with additional features. With over 17,000 unique oil seals in our database, you can cross-reference 180,000 part numbers of OEMs and manufacturers. In the Search Bar above, simply type the OEM/manufacturer part number alone (no need to type the name), and the oil seals matching that part number will be displayed.
As an example, this oil seal has a Shaft Size of 4″, a Bore Size of 5.000″, a Width Size of .375″, a Style of TB2, and is made of Viton material. Conversely, the same size oil seal in Metric has a Shaft Size of 101.6 mm, a Bore Size of 127 mm, and a Width Size of 9.52 mm.
OS/MOS: Designates if dimensions are displayed in inches or millimeters.
Shaft, Bore, Width: Dimensions displayed are actual size, rather than nominal.
Style: 2-5 characters in length (see our style chart at the bottom for details).
Material: There are several material options. Nitrile (Blank) Viton (V), Silicone (S), EPDM (E), Carboxylated Nitrile (X), HNBR (H), Polyacrylate (P), and Teflon (T).
Above, are all the components of an oil seal and all its naming conventions. Beyond selecting the correct size, the three primary selection criteria are Material, Lip and Case. If you have an oil seal you’d like custom designed and made, send us your specifications through our Oil Seal Design Form.
Material selection is important to the life of a radial shaft seal. The elastomer’s resistance to temperature, abrasion, chemicals, weather, sunlight, and ozone can affect a profile’s longevity and performance. The two most prevalent materials are Nitrile and Viton. See our Oil Seal Materials page for details on compounds and chemical compatibility.
The durometer of an oil seal is typically dependent on the material it is made with. Common oil seal materials along with their durometers are as follows:
- Nitrile (NBR) Oil Seal: 70 durometer (+/- 5)
- Viton (FKM) Oil Seal: 75 durometer (+/- 5)
- Polyacrylate (PA) Oil Seal: 75 durometer (+/- 5)
- Silicone Oil Seal: 80 durometer (+/- 5)
Lip selection is driven by the media type, shaft speed, pressure, temperature and contamination parameters. The media used in the majority of applications is either oil or grease. Lip designs generally include a spring when the media is oil because of its higher viscosity as compared to grease. There is also a double spring design when there is media on both sides of the oil seal. Lip designs can also include a secondary lip which purpose is to mitigate particulates from reaching the sealing lip. For additional protection of the oil seal from outside particulates, a V-Ring can be used in conjunction with the oil seal to eliminate particulates.
The most common and cost effective case materials are stamped from cold rolled carbon steel. The steel is then phosphate coated to aid in the molding process and to help eliminate corrosion during storage. A simply ‘L’ shaped geometry is the most cost effective case design but a number of case geometries are available to improve rigidity, positioning and removability. oil seal cases can also include rubber molded options which address such factors as corrosion, vibration and sealing characteristics.
A2 Case– The A2 design also has a metal outside diameter but includes an inner case which provide structural rigidity. This case design is used when the diameter of the seal is larger and rigidity is required to maintain structural integrity during installation.
The oil seal size is specified by three dimensions: the rotating shaft diameter, the housing bore diameter, and the width (thickness). Because of the oil seal’s purpose, the correct size is critical to performance. The inside diameter of an oil seal is sized slightly smaller than the shaft diameter in order to seal lubricants inside and prevent harmful contaminants from entering. Oil seals are offered in both metric and inch sizes to ensure the correct fit.
Shaft & Outside Diameter Tolerance (Inches)
|Shaft Tolerance in Inches|
|Nominal Shaft Diameter||Tolerances|
|Up to 4.000||+/-0.003|
|4.001 – 6.000||+/-0.004|
|6.001 – 10.000||+/-0.005|
|10.001 and larger||+/-0.006|
|Oil Seal Outside Diameter Standard Tolerances – Inches|
|Nominal Diameter||Tolerance||Metal Cased||Rubber Covered||Metal Cased||Rubber Covered|
|Up to 2.000||+/-.001||0.005||0.008||+/-.002||+/-.003|
|2.001 – 3.000||+/-.001||0.0055||0.01||+/-.0025||+/-.003|
|3.001 – 5.000||+/-.0015||0.0065||0.0105||+/-.003||+/-.003|
|5.001 – 7.000||+/-.0015||0.007||0.012||+/-.003||+/-.004|
|7.001 – 12.000||+/-.002||0.0085||0.0125||+/-.0035||+/-.004|
|12.001 – 20.000||+/-.003||0.012||0.015||+/-.005||+/-.005|
|20.001 – 40.000||+/-.004||0.013||0.018||+/-.005||+/-.006|
|40.001 – 60.000||+/-.006||0.016||0.02||+/-.006||+/-.007|
Shaft & Outside Diameter Tolerance (Millimeters)
|Shaft Tolerance in Metric (MM)|
|Nominal Shaft Diameter||Tolerance|
|0 – 3||+0.0 /-.060|
|3 – 6||+0.0 /-.075|
|6 – 10||+0.0 /-.090|
|10 – 18||+0.0 /-.110|
|18 – 30||+0.0 /-.130|
|30 – 50||+0.0 /-.160|
|50 – 80||+0.0 /-.190|
|80 – 120||+0.0 /-.220|
|120 – 180||+0.0 /-.250|
|180 – 250||+0.0 /-.290|
|250 – 315||+0.0 /-.320|
|315 – 400||+0.0 /-.360|
|400 – 500||+0.0 /-.400|
|Oil Seal Outside Diameter Standard Tolerances – Metric (MM)|
|Nominal Diameter||Tolerance||Metal Cased||Rubber Covered||Metal Cased||Rubber Covered|
|Up to 50||+.0039/-0.0||+.20/+0.08||+.30/+0.15||0.18||0.25|
|51 – 80||+.0046/-0.0||+.23/+0.09||+.35/+0.20||0.25||0.35|
|81 – 120||+.0054/-0.0||+.25/+0.10||+.35/+0.20||0.30||0.50|
|181 – 300||+.0075/-0.0||+.35/+0.15||+.45/+0.25||.025% of outside Dia.||0.80|
|301 – 440||+.0089/-0.0||+.45/+0.20||+.55/+0.30||.025% of outside Dia.||1.00|
Oil Seal Style Substitutions
Oil seals offer numerous style options. With the most popular styles, each can be categorized as Good, Better and Best. The manufacturer most often uses a Good (or Better) solution which was the most economical version that would perform to specifications. When replacing that oil seal, you can use the exact style or choice a Better or Best solution if your exact style is not in stock. In the charts below, you can always move up to Better and Best styles which can be substituted. Our goal is to provide our customers with the best product fast so we will stock the Better and Best styles and price them competitively.
Additional Oil Seal Options:
In addition to the Material, Lip, and Case selections, you can select to have a Stainless Steel Case and a Stainless Steel Spring. In those cases, you will find an additional indicator in the part number.
Installing an Oil Seal
Choosing the correct oil seal for your application is important. It is just as important that oil seals are installed properly, in which our step-by-step guide can be viewed here. Doing so ensures your desired oil seal fits and performs as intended. Oil leaks can happen even after replacing an oil seal if the shaft has wear groove damage, in which case restoration is possible with the installation of a shaft repair sleeve.
In the instance of wear groove damage on a crankshaft can be restored with the installation of a shaft repair sleeve.
Oil Seal Style Cross Reference Table
Oil seals are produced by a variety of manufacturers from around the globe. Part numbers vary greatly with manufacturers, so we have created a quick cross reference guide to cross oil seal lip and case designs. Sizing and material selection can be made on our e-commerce site or provide to an Inside Salesperson when placing an order. See the chart below:
|Global O-Ring and Seal||Case Design||Lip Design||Timken (National)||SKF/CR||Harwal||Garlock||Dichtomatik (TCM)|
|SC||Rubber OD||Single Lip w/ Spring||35||HMS5||A||92||SC|
|TC||Rubber OD||Double Lip w/ Spring||32||HMSA10||ADL||94||TC|
|VC||Rubber OD||Single Lip, No Spring||34||HM4||AO||91||VC|
|KC||Rubber OD||Double Lip, No Spring||KC|
|DC||Rubber OD||Two Spring Lips||DC||DC|
|SB||Metal OD, Rubber ID||Single Lip w/ Spring||HDS1/HDS2||SM||76||SM|
|TB||Metal OD, Rubber ID||Double Lip w/ Spring||TM||78||TM|
|VB||Metal OD, Rubber ID||Single Lip, No Spring||VM||71||VM|
|KB||Metal OD, Rubber ID||Double Lip, No Spring||KM||KM|
|DB||Metal OD, Rubber ID||Two Spring Lips||DM|
|SB2||Metal OD||Single Lip w/ Spring||48||CRW1||B||76||SB|
|TB2||Metal OD||Double Lip w/ Spring||47, 69||CRWA1||BDL||78||TB|
|VB2||Metal OD||Single Lip, No Spring||44||HM14||BO||71||VB|
|KB2||Metal OD||Double Lip, No Spring||49||BODL||KB|
|DB2||Metal OD||Two Spring Lips||DB||DB|
|SBR||Metal OD, Rubber ID, and Nose||Single Lip w/ Spring||35||SZ|
|TBR||Metal OD, Rubber ID, and Nose||Double Lip w/ Spring||33||TZ|
|VBR||Metal OD, Rubber ID, and Nose||Single Lip, No Spring||31||VZ||VZ|
|KBR||Metal OD, Rubber ID, and Nose||Double Lip, No Spring||KZ|
|DBR||Metal OD, Rubber ID, and Nose||Two Spring Lips|
|SA2||Metal OD w/ Reinforcing Plate||Single Lip w/ Spring||45||CRWH1||C||50||SA|
|TA2||Metal OD w/ Reinforcing Plate||Double Lip w/ Spring||41, 70||CRWHA1||CDL||TA|
|VA2||Metal OD w/ Reinforcing Plate||Single Lip, No Spring||CO||63||VA|
|KA2||Metal OD w/ Reinforcing Plate||Double Lip, No Spring||CODL||63||KA|
|DA2||Metal OD w/ Reinforcing Plate||Two Spring Lips||75||DA||DA|