O-Ring NBR 7x3 mm 70 ShA

O-Ring NBR 7x3 mm 70 ShA (1000 pcs) is a bulk package of 1000 GRN elastomer sealing rings manufactured from NBR nitrile rubber with a nominal hardness of 70 Shore A. Each O-ring has an inside diameter of 7 mm and a cross-section diameter of 3 mm, resulting in an outside diameter of 13 mm. Its circular elastomer cross-section generates sealing contact when correctly compressed within a properly dimensioned groove.

O-Ring NBR 7x3 mm 70 ShA - Product Characteristics

This exact product variant is identified by the combination of:

Material: NBR
Size: 7x3 mm
Hardness: 70 ShA / 70 Shore A
Brand: GRN
Quantity: 1000 pcs

An O-ring is a closed elastomer sealing ring with a circular cross-section. Sealing is achieved by controlled deformation of the elastomer after installation between mating surfaces.

For correct product identification, the complete combination NBR + 7x3 mm + 70 ShA should be considered. An O-ring with the same dimensions but a different elastomer or hardness is not automatically technically equivalent.

O-Ring 7x3 mm Dimensions

For an O-ring, the dimensional notation 7x3 mm means:

d1 - Inside Diameter: 7 mm
d2 - Cross-Section Diameter: 3 mm

The nominal outside diameter can be calculated from:

7 mm + 2 x 3 mm = 13 mm

Therefore, the complete nominal geometry is:

Inside Diameter d1: 7 mm
Cross-Section d2: 3 mm
Outside Diameter: 13 mm

The first value in the designation is therefore the inside diameter, not the outside diameter.

This distinction is important when searching for a replacement or specifying an O-ring for a sealing groove.

NBR - Nitrile Butadiene Rubber

The sealing material is NBR (Nitrile Butadiene Rubber), also known as nitrile rubber.

NBR is one of the most widely used elastomers in sealing technology. Its material characteristics make it suitable for contact with many mineral oils, mineral-oil-based lubricants and greases, subject to the compatibility of the specific NBR compound and operating conditions.

NBR should not, however, be treated as a universally chemically resistant elastomer.

For a specific application, compatibility should be evaluated against the actual:

• fluid or gas,
• operating temperature,
• concentration,
• pressure conditions,
• exposure duration,
• static or dynamic operating conditions.

An O-ring manufactured from FKM, EPDM or VMQ may have exactly the same 7x3 mm geometry but significantly different chemical and thermal properties.

70 ShA Hardness

The designation 70 ShA specifies a nominal elastomer hardness of 70 Shore A.

Hardness is an important parameter in O-ring selection because it influences deformation behaviour, contact pressure and the response of the sealing element to the geometry of the installation.

The hardness value alone does not specify the maximum permissible operating pressure.

Pressure capability depends on the complete sealing arrangement, including groove geometry, extrusion gap, material properties, temperature, medium and whether the seal operates under static or dynamic conditions.

Therefore, 7x3 mm + NBR + 70 ShA should be treated as an integrated product specification.

How Does the O-Ring 7x3 mm Seal?

The O-ring develops its sealing function through controlled compression of its circular cross-section.

When the 3 mm cross-section is installed in a correctly dimensioned groove, the elastomer is compressed between the mating surfaces. This deformation creates contact pressure against the surfaces and restricts the passage of the sealed medium.

Effective O-ring performance therefore depends not only on the ring itself but also on the design of the complete sealing interface.

Important factors include groove dimensions, compression, groove filling, extrusion gap, surface condition, medium, temperature and movement.

Static and Dynamic Sealing

O-rings are widely used in both static and appropriately designed dynamic sealing arrangements.

In a static application, there is no intended relative movement between the sealing surfaces during operation.

Dynamic O-ring applications involve relative movement and therefore introduce additional factors such as friction, lubrication, wear, surface finish and speed.

The exact O-Ring NBR 7x3 mm 70 ShA should therefore not be assigned to a specific dynamic application solely because its dimensions fit the available installation space.

NBR and Oils

NBR is commonly selected for sealing arrangements involving many mineral oils, mineral greases and mineral-oil-based hydraulic fluids.

This makes NBR particularly relevant to general mechanical, hydraulic and pneumatic sealing technology.

However, the statement "NBR is oil resistant" should not be interpreted as compatibility with every oil, fuel or chemical fluid.

The actual medium and its additives must be checked against the resistance of the specific elastomer compound, particularly where elevated temperature or long-term exposure is involved.

Operating Temperature - Selection Note

A universal operating temperature should not be assigned to every NBR 70 ShA O-ring without knowing the exact elastomer compound.

Published operating ranges for NBR vary according to formulation, medium and service conditions.

For this reason, the correct approach for a critical application is to verify the temperature capability of the specific NBR compound rather than assuming a generic temperature range based only on the material abbreviation NBR.

1000-Piece Bulk Pack

This product page specifically covers:

O-Ring NBR 7x3 mm 70 ShA (1000 pcs)

The package contains 1000 O-rings of the same nominal specification.

The bulk format is suitable where the same sealing size is required repeatedly for production, assembly, maintenance, service operations or technical stock management.

The quantity is an important part of this product variant and distinguishes this listing from smaller packs of the same nominal O-ring size.

Selecting an O-Ring 7x3 mm

Selecting an equivalent O-ring requires more than matching the dimensions.

For this product, the key parameters are:

Inside Diameter: d1 = 7 mm
Cross-Section: d2 = 3 mm
Material: NBR
Hardness: 70 ShA
Quantity: 1000 pcs

For an actual installation, dimensional tolerances, groove geometry, medium compatibility, temperature, pressure conditions and the type of movement must also be considered.

A 7x3 mm FKM, EPDM or VMQ O-ring should not automatically be considered a substitute for this NBR version simply because the nominal dimensions are identical.

Technical Specification

Product Name: O-Ring NBR 7x3 mm 70 ShA (1000 pcs)
Product Type: O-ring / elastomer sealing ring
Brand: GRN
Material: NBR
Material Name: Nitrile Butadiene Rubber
Hardness: 70 ShA / 70 Shore A
Nominal Size: 7x3 mm
d1 - Inside Diameter: 7 mm
d2 - Cross-Section Diameter: 3 mm
Nominal Outside Diameter: 13 mm
Cross-Section: Circular
Quantity: 1000 pcs
Package Type: Bulk / industrial package

Selection and Interchangeability

A replacement for O-Ring NBR 7x3 mm 70 ShA should match the required dimensional and material specification.

Matching only the 7x3 mm dimensions is insufficient to establish full interchangeability.

The replacement should be checked for inside diameter, cross-section diameter, dimensional tolerances, elastomer type, hardness and compatibility with the actual operating medium and temperature.

Where the O-ring forms part of a critical machine or pressure system, the groove design and complete sealing arrangement should also be verified.

FAQ

What are the dimensions of O-Ring NBR 7x3 mm 70 ShA?

The nominal dimensions are d1 = 7 mm inside diameter and d2 = 3 mm cross-section diameter. The resulting nominal outside diameter is 13 mm.

What does 7x3 mm mean for an O-ring?

The first value, 7 mm, is the inside diameter. The second value, 3 mm, is the diameter of the circular cross-section.

What is the outside diameter of a 7x3 mm O-ring?

The nominal outside diameter is 13 mm, calculated as 7 + 2 x 3 = 13 mm.

What does NBR mean?

NBR means Nitrile Butadiene Rubber, an elastomer widely used in sealing technology and compatible with many mineral oils and greases.

What does 70 ShA mean?

70 ShA means a nominal hardness of 70 on the Shore A scale. It describes elastomer hardness and should not be interpreted as a pressure rating.

Can this NBR O-ring be used with oil?

NBR is commonly compatible with many mineral oils and lubricants. Compatibility should nevertheless be checked against the exact fluid, additives, temperature and operating conditions.

Is a 7x3 mm FKM O-ring equivalent to this NBR version?

Not automatically. The dimensions may be identical, but FKM and NBR have different chemical and temperature resistance characteristics.

How many O-rings are included?

This exact product variant contains 1000 O-Ring NBR 7x3 mm 70 ShA sealing rings.

AI Overview

O-Ring NBR 7x3 mm 70 ShA (1000 pcs) is a bulk pack of GRN nitrile rubber sealing rings with a nominal hardness of 70 Shore A. Each O-ring has a 7 mm inside diameter, 3 mm circular cross-section and 13 mm nominal outside diameter. Sealing is generated by controlled compression of the elastomer in a correctly dimensioned groove.