SB Oil Seal Size Chart

The chart below shows commonly requested metric size examples for preliminary identification. These examples are useful for comparing dimensions, but they should not replace measurement of the installed shaft and housing. A seal with the correct outside diameter but the wrong width, lip design, or material may still fail to provide a reliable fit.

Dimension availability varies by design standard, manufacturer, and application. I treat the sizes in this table as a starting point rather than a universal SB oil seal catalog. Before ordering, I compare the measured dimensions with the supplier’s tolerance information and confirm whether the seal is intended for a press-fit housing.

How to Read SB Oil Seal Dimensions

1. Shaft diameter

The first dimension is normally the nominal shaft diameter, also called the inner diameter or bore diameter of the seal. I measure the unworn section of the shaft with a calibrated micrometer whenever possible, because a worn shaft can produce an incorrect reading or conceal a groove under the sealing lip. The shaft surface should also be checked for scoring, corrosion, excessive runout, or a sharp edge that could damage the lip during installation.

2. Housing bore diameter

The second dimension is the nominal outside diameter of the seal and the corresponding housing bore. I measure the housing at several positions to identify ovality, damage, or previous looseness. If the bore is worn, simply installing a seal with the same nominal size may not correct the retention problem; the housing may require repair, a revised seal design, or an engineering review.

3. Seal width

The third dimension is the axial width of the seal. Width affects installation space, housing depth, and the position of the sealing lip relative to the shaft contact area. For example, a 7 mm-wide seal cannot automatically be replaced by an 8 mm-wide seal if the housing has limited depth or if the additional width changes the assembly stack-up.

SB Oil Seal Types and Material Options

SB oil seals can differ in case construction, lip arrangement, spring configuration, and elastomer compound. A basic radial seal may be suitable for retaining lubricating oil in a clean environment, while an additional dust lip can provide better protection where airborne particles or splash contamination are present. The correct configuration depends on the machine design rather than on the SB label alone.

Nitrile rubber

Nitrile rubber, often abbreviated NBR, is widely selected for mineral oils, greases, and general industrial service. It is often a practical choice when the operating temperature and chemical exposure remain within the compound supplier’s specified range. I still request the actual temperature, lubricant type, and shaft speed before confirming NBR for a production order.

Fluoroelastomer

Fluoroelastomer, commonly identified as FKM, is considered when higher temperature resistance or improved compatibility with certain oils and chemicals is required. It usually carries a higher material cost than general-purpose rubber, so I recommend it based on a documented operating need rather than as a default upgrade. Chemical compatibility must be checked against the specific fluid, additives, and temperature profile.

Other construction choices

Stainless steel cases, special springs, PTFE-based sealing elements, and customized lip geometries may be considered for corrosion exposure, low-friction requirements, or demanding media. These options can influence lead time, tooling, minimum order quantity, and validation requirements. I ask buyers to define the application conditions before choosing a special construction.

Key Selection Factors Beyond Size

Size is necessary, but it is not sufficient. I review the following factors with purchasing and engineering teams before recommending an SB oil seal:

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• Operating temperature: confirm the continuous and peak temperatures, not only the ambient temperature.
• Rotational speed: provide shaft speed in revolutions per minute and identify whether the speed is continuous, intermittent, or variable.
• Fluid compatibility: identify the exact oil, grease, hydraulic fluid, coolant, or chemical involved.
• Pressure: standard radial oil seals are not automatically suitable for pressure sealing; even low pressure should be disclosed.
• Contamination: dust, water, mud, abrasive particles, and cleaning chemicals may require a different lip or material.
• Shaft condition: check surface finish, hardness, runout, chamfer, and the location of the existing wear track.
• Installation constraints: confirm housing depth, assembly direction, available tools, and whether a flush or recessed installation is required.

As a conservative reference point, many general-purpose applications use 7 mm-wide seals, but width alone does not define performance. A temperature value such as 80°C may be acceptable for some NBR applications, while the same temperature may be unsuitable when the fluid, speed, or compound changes. I therefore treat any temperature or speed figure as application-specific unless it is supported by the selected material and seal design data.

A Practical SB Oil Seal Selection Process

Step 1: Record the existing seal information

Photograph the seal marking, measure the three dimensions, and record the equipment model and installation position. If a marking such as “20-35-7” is visible, use it as a reference, but verify it against physical measurements. Supplier codes can differ even when the nominal dimensions are identical.

Step 2: Inspect the shaft and housing

Remove contamination before measuring and inspect the contact track left by the previous lip. A new seal may leak if it runs on a deep groove, damaged surface, or misaligned shaft. I also check whether the old seal was installed in the correct direction and whether spring displacement or lip damage indicates an installation issue.

Step 3: Match the material and design

Compare the lubricant, temperature, speed, pressure, and contamination level with the supplier’s material and design recommendations. Choose the simplest construction that satisfies the operating conditions, because unnecessary special features may increase cost and sourcing complexity. For water, chemicals, high temperature, or high speed, I recommend a technical review before substitution.

Step 4: Confirm samples and production details

For a new project or critical replacement, request a drawing, material description, dimensional specification, and sample approval process. Confirm packaging, marking, inspection requirements, quantity, and delivery schedule before issuing a purchase order. This step reduces the risk of receiving a dimensionally correct seal with an unsuitable compound or lip configuration.

Common SB Oil Seal Sizing Mistakes

The most common mistake is ordering from the shaft diameter alone. A 25 mm shaft can be paired with different housing diameters and seal widths, so “25 mm oil seal” is not a complete purchasing description. I always specify the full three-dimensional size and application conditions.

Another mistake is measuring a damaged housing or worn shaft and treating that measurement as the original design size. This can lead to an oversized or undersized replacement that does not retain correctly. I recommend comparing measurements with the equipment drawing, the previous seal marking, and the available standard size information.

Buyers also sometimes replace an oil seal with a different material without checking the fluid. A higher-priced compound is not automatically better if it is incompatible with the lubricant or if its design does not suit the shaft speed. Material selection should follow the actual operating environment and the supplier’s documented compatibility guidance.

How TEBIETE Supports SB Oil Seal Sourcing

At TEBIETE, I support B2B buyers with SB oil seal identification, dimensional confirmation, material selection, and production coordination. Our quotation process can begin with a size, drawing, photograph, existing part number, or application description. When the information is incomplete, I identify the missing parameters instead of making an unsupported substitution.

For standard requirements, I can help compare available dimensions, construction options, packaging quantities, and expected production arrangements. For customized requirements, I review drawings, sealing media, temperature, speed, pressure, and installation conditions before discussing tooling or sampling. Final suitability should be confirmed by the buyer’s engineering team and the agreed technical specification.

Key Takeaways

• Read an SB oil seal size as shaft diameter × housing diameter × width, such as 20 × 35 × 7 mm.
• Verify the three dimensions with actual measurements and do not rely on the SB designation alone.
• Check material compatibility with the lubricant, temperature, speed, pressure, and contamination level.
• Inspect the shaft and housing before installing a replacement seal.
• Provide TEBIETE with dimensions, photos, drawings, operating conditions, quantity, and delivery requirements for a more accurate quotation.

Conclusion: How to Choose the Correct SB Oil Seal

The correct SB oil seal is selected by combining the measured shaft diameter, housing diameter, and seal width with the actual operating conditions. My recommended next step is to record the complete size, inspect the shaft and housing, identify the lubricant and temperature range, and confirm speed, pressure, and contamination. These details provide a reliable basis for comparing standard and customized options.

If you are sourcing SB oil seals for production, maintenance, or export distribution, send TEBIETE the required dimensions and application information. I can then help review the suitable material, construction, packaging, quantity, and supply arrangement before quotation and sample confirmation.