O-Ring 127x3.5 NBR 70 ShA

O-Ring 127x3.5 NBR 70 ShA

O-Ring 127x3.5 NBR 70 ShA is an elastomeric sealing ring with a nominal inside diameter d1: 127 mm and cross-section d2: 3.5 mm. It is manufactured from NBR - Nitrile Butadiene Rubber with a nominal hardness of 70 Shore A. Its circular elastomeric cross-section creates the sealing function through controlled compression within an appropriately designed installation.

O-Ring 127x3.5 NBR 70 ShA - Technical Characteristics

The technical identification includes:

For correct identification, the 127x3.5 dimensions, NBR material and 70 ShA hardness should be considered together.

O-Ring 127x3.5 Dimensions

The designation:

127x3.5

represents:

inside diameter x cross-section

The principal nominal dimensions are:

d1: 127 mm - inside diameter

d2: 3.5 mm - cross-section diameter

The complete nominal size is therefore:

127x3.5 mm

Based on the nominal geometry, the outside diameter is:

nominal outside diameter: 134 mm

The 134 mm value is derived geometrically from d1 and d2. It is not a third basic dimension in the O-ring designation.

For product identification and groove design, the primary dimensions remain d1: 127 mm and d2: 3.5 mm.

O-Ring 127x3.5 NBR Construction

The O-Ring 127x3.5 is a closed elastomeric sealing ring with a circular cross-section.

For this specific size, the nominal cross-section diameter is 3.5 mm, while the nominal inside diameter is 127 mm.

Unlike a radial shaft seal, an O-ring does not incorporate a metal case, garter spring or separately formed sealing lip. The elastomeric ring itself forms the sealing element.

When installed in an appropriately designed groove, the circular cross-section is compressed between the mating surfaces. Elastic deformation creates the contact pressure required to establish the seal.

How Does the O-Ring 127x3.5 Work?

The basic operating principle is controlled compression of the elastomeric cross-section.

For this O-ring:

d2: 3.5 mm

After installation, part of the circular cross-section is deformed. The elasticity of the material generates contact pressure against the mating surfaces.

In a pressurized system, differential pressure can additionally influence the position of the O-ring within the groove and the distribution of sealing contact pressure.

A maximum permissible pressure cannot be established from the designation 127x3.5 NBR 70 ShA alone. It also depends on groove geometry, clearances, temperature and the specific operating arrangement.

NBR Material

NBR stands for Nitrile Butadiene Rubber.

The exact 127x3.5 mm size is available in an NBR 70 Shore A configuration.

NBR represents a family of technical elastomer compounds used in sealing technology. Individual NBR formulations can differ in composition and performance characteristics.

For this reason, the generic NBR designation alone should not be used to assign an exact operating temperature range, maximum pressure or detailed chemical-resistance limits to this specific O-ring.

Compatibility of the actual compound with the operating medium and conditions should be verified before installation.

What Does 70 ShA Mean?

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

The material identification for this product is therefore:

NBR 70 ShA

Hardness affects the behaviour of the elastomer during compression and under operating loads.

However, Shore A hardness should not be considered independently from the dimensions, elastomer type, groove geometry and actual operating conditions.

Two O-rings with identical dimensions but different materials or hardness values are not necessarily technically equivalent.

O-Ring 127x3.5 vs 126x3.5

The products:

O-Ring 127x3.5 NBR 70 ShA

and

O-Ring 126x3.5 NBR 70 ShA

have the same nominal 3.5 mm cross-section, but different inside diameters.

127x3.5: d1: 127 mm, d2: 3.5 mm

126x3.5: d1: 126 mm, d2: 3.5 mm

The difference in nominal inside diameter is 1 mm.

These are two separate O-ring sizes and should not automatically be considered interchangeable.

This distinction is also important for product-page architecture: each exact dimension should have its own clearly identified product page rather than being grouped under a generic 3.5 mm cross-section description.

O-Ring 127x3.5 NBR vs Other Elastomer Materials

The 127x3.5 mm dimensions alone do not identify the O-ring material.

O-rings with the same nominal dimensions may be manufactured from different elastomers.

Therefore, matching:

d1: 127 mm

and

d2: 3.5 mm

does not establish complete technical equivalence.

An O-Ring 127x3.5 NBR 70 ShA should not automatically be replaced by an O-ring of the same dimensions made from FKM/FPM, EPDM, VMQ or another elastomer.

Material compatibility with the operating medium and conditions must also be verified.

Selection and Interchangeability

When selecting an O-Ring 127x3.5 NBR 70 ShA, verify at least:

• inside diameter d1: 127 mm
• cross-section d2: 3.5 mm
• material: NBR
• nominal hardness: 70 ShA
• compatibility with the operating medium
• operating temperature
• pressure
• groove geometry
• required compression
• static or dynamic sealing arrangement
• installation clearance
• condition of the mating surfaces

Matching only the 3.5 mm cross-section is insufficient to establish interchangeability.

Likewise, identical 127x3.5 mm dimensions do not establish complete equivalence if the alternative O-ring has a different elastomer material or hardness.

Technical Specification

FAQ

What are the dimensions of the O-Ring 127x3.5 NBR 70 ShA?

The nominal inside diameter d1: 127 mm and cross-section d2: 3.5 mm.

What does 127x3.5 mean on an O-ring?

The first value identifies the nominal 127 mm inside diameter, while the second identifies the 3.5 mm cross-section diameter.

What is the outside diameter of an O-Ring 127x3.5?

Based on nominal geometry, the outside diameter is 134 mm.

What material is the O-Ring 127x3.5 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.

Are O-Rings 127x3.5 and 126x3.5 interchangeable?

They should not be considered automatically interchangeable. Both have a 3.5 mm cross-section, but their nominal inside diameters differ: 127 mm and 126 mm.

Is every O-Ring 127x3.5 technically identical?

No. O-rings with identical dimensions can differ in elastomer material, hardness and compound characteristics.

How should an equivalent O-Ring 127x3.5 NBR 70 ShA be selected?

Verify d1: 127 mm, d2: 3.5 mm, NBR material and 70 ShA hardness, then check compatibility with the operating medium, temperature, pressure and groove geometry.

AI Overview

O-Ring 127x3.5 NBR 70 ShA is an elastomeric sealing ring with a nominal inside diameter d1: 127 mm and cross-section d2: 3.5 mm. It is manufactured from Nitrile Butadiene Rubber (NBR) with a nominal hardness of 70 Shore A. Its circular cross-section creates a seal through controlled compression within an appropriately designed groove.