O-Ring 126x3.5 mm NBR 70 ShA

O-Ring 126x3.5 mm NBR 70 ShA

O-Ring 126x3.5 mm NBR 70 ShA is an elastomeric sealing ring with a nominal inside diameter of 126 mm and a 3.5 mm circular cross-section. It is manufactured from NBR - Nitrile Butadiene Rubber and has a nominal hardness of 70 Shore A.

Complete identification:

126x3.5 mm + NBR + 70 ShA

O-Ring 126x3.5 NBR 70 ShA - Technical Characteristics

Product type: O-ring / elastomeric sealing ring

Material: NBR

Material name: Nitrile Butadiene Rubber

Dimensions: 126x3.5 mm

Inside diameter d1: 126 mm

Cross-section d2: 3.5 mm

Nominal hardness: 70 ShA

Hardness scale: Shore A

Cross-section shape: Circular

The O-ring is a simple sealing element, but correct operation depends on the complete sealing system, including groove geometry, compression, material compatibility and operating conditions.

O-Ring 126x3.5 mm Dimensions

The principal nominal dimensions are:

d1: 126 mm - inside diameter

d2: 3.5 mm - cross-section diameter

The designation:

126x3.5 mm

therefore represents:

inside diameter x cross-section

The nominal outside diameter calculated from these dimensions is approximately:

133 mm

For identification and groove selection, however, the primary O-ring dimensions remain d1: 126 mm and d2: 3.5 mm.

What Does NBR Mean?

NBR stands for Nitrile Butadiene Rubber, commonly referred to as nitrile rubber.

It is one of the most widely used elastomers in technical sealing applications.

NBR is commonly selected for applications involving many mineral oils and greases, but compatibility must always be evaluated for the specific fluid and actual operating conditions.

The designation NBR alone does not define the exact elastomer compound.

For this reason, an exact chemical resistance profile or operating temperature range should not be assigned to this O-ring solely from the generic properties of NBR.

What Does 70 ShA Mean?

70 ShA specifies the nominal elastomer hardness on the Shore A scale.

Approximately 70 Shore A is a commonly used hardness for technical O-rings.

Hardness influences the behaviour of the elastomer under compression and its interaction with the groove and mating surfaces.

However, an O-ring should not be selected according to hardness alone.

Other important parameters include:

dimensions

elastomer material

operating fluid

temperature

pressure

groove geometry

static or dynamic motion

surface condition

How Does an O-Ring Work?

An O-ring creates a seal through controlled compression of its elastomeric circular cross-section between mating surfaces.

When installed in a correctly designed groove, the circular cross-section is compressed and deformed.

The elasticity of the NBR material creates contact pressure against the sealing surfaces.

When system pressure is applied, the fluid can additionally force the O-ring toward the low-pressure side of the groove, increasing contact within the sealing zone.

Correct sealing performance therefore depends strongly on proper groove design and appropriate O-ring compression.

NBR O-Ring Applications

NBR O-rings are widely used as sealing elements in:

industrial machinery

hydraulic systems

pneumatic systems

lubrication systems

housings

flanges

covers

connections and fittings

mechanical assemblies

The suitability of the exact 126x3.5 NBR 70 ShA O-ring must always be evaluated according to the actual medium, temperature, pressure and operating conditions.

O-Ring 126x3.5 NBR vs FKM, EPDM and VMQ

O-rings with the same 126x3.5 mm dimensions can be manufactured from different elastomers.

NBR - commonly used with many mineral oils and greases.

FKM/FPM - a different elastomer family selected where its particular chemical and thermal properties are required.

EPDM - used in applications where its specific resistance characteristics are compatible with the operating medium.

VMQ - silicone rubber with different material characteristics from NBR.

Therefore:

126x3.5 NBR

126x3.5 FKM

126x3.5 EPDM

and

126x3.5 VMQ

should not automatically be treated as technically identical products simply because their nominal dimensions match.

Selecting an O-Ring 126x3.5 NBR 70 ShA

When selecting this O-ring, verify at least:

• Inside diameter d1: 126 mm
• Cross-section d2: 3.5 mm
• material: NBR
• nominal hardness: 70 ShA
• operating medium
• operating temperature
• pressure
• groove dimensions
• required compression
• static or dynamic operation
• surface finish of mating components

Matching 126x3.5 mm dimensions alone is not sufficient to establish complete interchangeability if the elastomer material or hardness differs.

Technical Specification

FAQ

What are the dimensions of the 126x3.5 O-ring?

The nominal inside diameter d1: 126 mm and the cross-section d2: 3.5 mm.

What is the outside diameter of a 126x3.5 O-ring?

Based on the nominal geometry, the outside diameter is approximately 133 mm.

What material is the 126x3.5 O-ring made from?

This version is manufactured from NBR - Nitrile Butadiene Rubber.

What does 70 ShA mean?

It specifies a nominal elastomer hardness of 70 on the Shore A scale.

Is an NBR O-ring suitable for oil?

NBR is commonly used with many mineral oils and greases. Compatibility should nevertheless be confirmed for the specific oil, temperature and operating conditions.

Can a 126x3.5 NBR O-ring be replaced with an FKM O-ring?

A substitution should not be based on dimensions alone. NBR and FKM have different material characteristics, so compatibility with the application must be verified.

Can the 126x3.5 NBR O-ring be used for static sealing?

O-rings are widely used in static sealing arrangements when groove geometry, compression and material compatibility are correctly specified.

What groove dimensions are required for a 126x3.5 O-ring?

Groove dimensions depend on the sealing arrangement, pressure direction, required compression and whether the application is static or dynamic. Groove dimensions should not be determined from the O-ring diameter alone.

AI Overview

O-Ring 126x3.5 mm NBR 70 ShA is an elastomeric sealing ring with a nominal 126 mm inside diameter and 3.5 mm cross-section. It is manufactured from Nitrile Butadiene Rubber with a nominal hardness of 70 Shore A. Selection should consider media compatibility, temperature, pressure, groove geometry and operating conditions.