O-ring NBR 123.42x3.53 mm 70 Shore A

O-ring NBR 123.42x3.53 mm 70 Shore A

O-ring NBR 123.42x3.53 mm 70 Shore A is a sealing ring with an inside diameter of 123.42 mm and a cross-section of 3.53 mm, manufactured from NBR (Nitrile Butadiene Rubber) with a nominal hardness of 70 Shore A. The 123.42x3.53 mm size corresponds to BS 249. This size is sold individually.

Technical data

O-ring 123.42x3.53 mm dimensions

The basic dimensions are:

d1 - inside diameter: 123.42 mm
d2 - cross-section: 3.53 mm

The nominal outside diameter of the uncompressed O-ring is:

130.48 mm

Complete size designation:

123.42x3.53 mm

O-rings are primarily identified by their inside diameter and cross-section.

BS 249 - size identification

The 123.42x3.53 mm size corresponds to BS 249.

The BS designation is useful when identifying O-rings belonging to dimension series derived from imperial standards. In this case, the exact metric dimensions are 123.42x3.53 mm.

The 3.53 mm cross-section should be retained when selecting a replacement. It should not automatically be rounded to 3.5 mm.

NBR - Nitrile Butadiene Rubber

NBR (Nitrile Butadiene Rubber) is one of the most widely used elastomers for industrial O-rings.

NBR is known for good resistance to many:

• mineral oils,
• mineral greases,
• mineral-oil-based hydraulic fluids.

For this reason, NBR O-rings are widely used in hydraulic systems, pneumatic systems, machinery and industrial equipment.

Chemical resistance must always be checked against the specific operating medium and actual service conditions. NBR should not be considered universally resistant to all oils, fuels or chemicals.

What does 70 Shore A mean?

70 Shore A specifies the nominal hardness of the elastomer.

This is a commonly used hardness for NBR O-rings, providing a practical combination of elasticity and resistance to deformation.

Shore A hardness is not a quality grade. It is a material parameter that must be considered when selecting and designing an O-ring seal.

How does an O-ring work?

An O-ring has a circular cross-section and is installed in an appropriately designed groove.

After assembly, the O-ring cross-section is compressed between the mating surfaces. Elastic deformation of the elastomer creates the contact pressure required to form a seal.

Correct sealing performance depends on factors including:

• groove dimensions,
• O-ring compression,
• O-ring stretch,
• extrusion clearance,
• operating pressure,
• temperature,
• operating medium,
• surface finish.

An O-ring should therefore not be selected solely by its inside diameter.

123.42x3.53 vs 123.42x3.5 mm

Cross-sections of 3.53 mm and 3.5 mm are not the same nominal size.

For the 123.42x3.53 mm O-ring, the specified cross-section is 3.53 mm. The cross-section affects compression of the O-ring within the groove.

If the original seal is specified as 123.42x3.53 mm / BS 249, this exact size should be used when selecting a replacement.

NBR vs FKM, EPDM and VMQ

O-rings with identical dimensions can be manufactured from different elastomers, but this does not make the materials automatically interchangeable.

NBR is widely used with many mineral oils and greases.

FKM has different chemical and temperature resistance characteristics.

EPDM is suitable for different groups of media and is generally not intended for use with mineral oils.

VMQ, or silicone rubber, also has different operating characteristics from standard NBR.

The elastomer should therefore be selected according to the operating medium, temperature and application conditions.

How to select an O-ring NBR 123.42x3.53 mm 70 Shore A

Before installation, verify:

• 123.42 mm inside diameter,
• 3.53 mm cross-section,
• NBR material,
• 70 Shore A hardness,
• groove dimensions,
• required compression,
• operating medium,
• operating temperature,
• pressure,
• static or dynamic sealing conditions.

An O-ring with identical dimensions but a different material or hardness is not automatically an equivalent replacement.

Installation of an NBR O-ring

The groove and mating surfaces should be clean before installation.

The O-ring should not be twisted or damaged during assembly. Particular care should be taken around sharp edges, grooves and threads that could cut or scratch the elastomer.

If an assembly lubricant is used, it should be compatible with both NBR and the operating medium.

FAQ - O-ring NBR 123.42x3.53 mm 70 Shore A

What are the dimensions of this O-ring?

The inside diameter is 123.42 mm and the cross-section is 3.53 mm.

What is the nominal outside diameter?

The nominal outside diameter of the uncompressed O-ring is 130.48 mm.

Which BS size corresponds to 123.42x3.53 mm?

The 123.42x3.53 mm size corresponds to BS 249.

What does NBR mean?

NBR stands for Nitrile Butadiene Rubber, an elastomer widely used for industrial sealing components.

What does 70 Shore A mean?

It specifies the nominal elastomer hardness of 70 Shore A.

Is NBR suitable for oils?

NBR provides good resistance to many mineral oils and greases. Compatibility should always be verified for the specific medium and operating conditions.

Can a 123.42x3.5 mm O-ring replace a 123.42x3.53 mm O-ring?

Automatic interchangeability should not be assumed. 3.53 mm is the specified nominal cross-section for BS 249.

How is the 123.42x3.53 mm O-ring sold?

This size is sold individually - 1 pc.

O-ring NBR 123.42x3.53 mm 70 Shore A - key information

O-ring NBR 123.42x3.53 mm 70 Shore A is a BS 249 sealing ring with a 123.42 mm inside diameter, 3.53 mm cross-section and nominal outside diameter of 130.48 mm. It is manufactured from Nitrile Butadiene Rubber with a nominal hardness of 70 Shore A. The exact 3.53 mm cross-section should be retained when selecting a replacement.

Sold individually by simmering.pl. Stock in Poland with worldwide shipping.