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.


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 that are functionally compatible but with additional features. With over 50,000 unique oil seals in our database, you can cross-reference 215,000 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 part number that corresponds to a Shaft Size of 3”, a Bore Size of 4”, a Width Size of 0.625”, a Style of TB2, and is made of Viton material. Conversely, the same size oil seal in Metric has a Shaft Size of 76.20 mm, a Bore Size of 101.60 mm, and a Width Size of 15.88 mm.

OS/MOS: Designates if dimensions are displayed in inches or millimeters

Size #: Corresponds to sizes found on our Oil Seal Size Chart. The interactive chart will display matching sizes based on the dimensions input for Shaft, Bore, and Width. The Oil Seal Size # is hyperlinked to our online store, which will display all sizes matching the selection.

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).

Box: If a BX appears at the end of the part number, that oil seal will be in a box.

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Selecting the Right Oil Seal

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:

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:

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.

‘S’ Lip – single lip with spring. The spring is to ensure sealing of oils versus grease. Used in more benign environments.




‘T’ Lip – dual lip with spring. The lip design includes a secondary dust lip to minimize particulates from entering the sealing region. This is the most common lip design.



‘V’ Lip – single lip without spring. This lip is designed for grease applications because the high viscosity of grease does not require a spring.




‘K’ Lip – dual lip without a spring. This lip is designed for grease applications and include a secondary dust lip to minimize particulates from entering the sealing region.




‘D’ Lip – dual lip and dual spring lip. This lip is designed when there is media on both sides of the oil seal.


Case Selection:

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.

B2 CaseThe most economical design and popular design (simple ‘L’ shape). It has a metal outside diameter.




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.



C Case– The outside of this case is rubber coated. This design is often used when a seal will be removed frequently or if sealing of bore and oil seal is of concern.




B Case– The B design is the same as the B2 except that a rubber inner coating is added to protect case from media.




BR Case– The BR design is same as B with additional rubber coating on the leading edge of the case. This additional rubber coating is to ensure sealing when the oil seal is seated in the groove.

Size Selection:

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. Oil seals can be looked up by size using the Oil Seal Size Chart, which narrows down oil seals as dimensions are entered.

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
Bore Press-Fit Allowance Tolerance
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)
Bore Press-Fit Allowance Eccentricity
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
121- 180 +.0063/-0.0 +.28/+0.15 +.45/+0.25 0.40 0.65
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.

Exhibit 1:

Exhibit 2:

Exhibit 3:

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