O-Ring Cords

O-Ring Cord NBR FKM EPDM VMQ - Custom Sealing Cord

O-Ring Cord NBR FKM EPDM VMQ - Sealing Cord for Custom O-Rings

O-ring cord is a continuous elastomeric profile with a round cross-section, used primarily to manufacture custom-size or large-diameter sealing rings. The cord can be cut to the required length and its ends appropriately joined to create a closed sealing ring for a specific groove or application. O-ring cord is available in materials such as NBR, FKM/FPM, EPDM and VMQ/MVQ silicone, allowing the material to be selected according to oil exposure, water, temperature, weathering and other operating conditions.

What Is O-Ring Cord?

O-ring cord, also known as O-ring cord stock, round sealing cord or rubber O-ring cord, is supplied as a continuous elastomeric profile rather than as a finished molded ring.

Its primary dimensional parameter is the cross-sectional diameter.

For example:

O-Ring Cord 2 mm

means a round elastomer profile with a nominal cross-section of 2 mm.

Unlike a molded O-ring, cord stock does not have a predefined inside diameter.

It can be cut to a selected length and joined to create a sealing ring with the required circumference.

What Is O-Ring Cord Used For?

O-ring cord is particularly useful when:

a required O-ring diameter is non-standard
a very large sealing ring is needed
the correct molded O-ring is difficult to source
machinery must be repaired quickly
maintenance teams require dimensional flexibility
a custom sealing groove is used
a prototype or one-off seal is required
large housings or covers must be sealed

One cord cross-section can therefore be used to produce many different ring diameters.

O-Ring Cord vs Molded O-Ring

O-ring cord and a conventional molded O-ring are not identical solutions.

A molded O-ring is manufactured as a continuous closed ring without a joined section.

O-ring cord must be cut and its ends joined.

The principal advantage of cord stock is the ability to produce custom and very large diameters.

A molded O-ring is generally preferable when the required standard size is available and the application benefits from a continuous, joint-free ring.

O-Ring Cord by the Metre

O-ring cord can be used to manufacture seals with a length adapted to the actual requirement.

This makes it particularly useful for:

maintenance departments
MRO
machine service companies
industrial workshops
machine builders
production facilities
prototype departments
technical spare parts warehouses

Keeping several commonly used cord cross-sections in stock can reduce the need to hold every possible molded O-ring diameter.

How to Select O-Ring Cord Diameter

The main dimensional parameter is the diameter of the round cross-section.

Typical designations may include:

1.5 mm O-ring cord
2 mm O-ring cord
2.5 mm O-ring cord
3 mm O-ring cord
4 mm O-ring cord
5 mm O-ring cord

as well as many other sizes.

The cross-section should correspond to the sealing groove geometry and required compression.

A cord diameter should not be selected solely from the approximate diameter of an old seal.

How to Make an O-Ring from Cord

A typical procedure includes:

selecting the correct material and cross-section
determining the required cord length
cutting the cord accurately
preparing the cut ends
joining the ends using a suitable method
allowing the joint to cure or stabilize as required
checking the finished ring geometry

Cutting accuracy and joint quality are critical.

Misaligned ends or uneven cuts can create a local discontinuity in the sealing surface.

Joining O-Ring Cord

One common method of producing a closed ring is bonding the prepared cord ends.

The adhesive or joining system must be compatible with the specific elastomer.

One bonding product should not automatically be assumed suitable for:

NBR
FKM
EPDM
VMQ silicone

Joint performance depends on:

elastomer type
cutting accuracy
surface preparation
adhesive chemistry
curing time
operating temperature
final mechanical load

The bonded area may have different mechanical properties from the continuous molded elastomer.

Can O-Ring Cord Replace a Molded O-Ring?

In many static sealing applications, it can provide a practical solution, but it is not always a direct equivalent to a molded O-ring.

Extra evaluation is required for:

high-pressure systems
reciprocating applications
rotary applications
high-speed movement
pressure pulsation
safety-critical systems
aggressive chemical media
applications requiring specific approvals

The joined section is an additional feature of the finished seal and should be considered when evaluating performance.

O-Ring Cord for Static Sealing

One of the most natural uses of O-ring cord is in large or non-standard static sealing applications.

Potential applications include:

machine covers
housings
flanges
tanks
access covers
large enclosures
industrial equipment
service covers

In a static arrangement, the bonded joint is not continuously exposed to relative motion against the mating surface.

This generally makes static service more suitable for cord-made sealing rings than demanding dynamic operation.

NBR O-Ring Cord

NBR, or Nitrile Butadiene Rubber, is one of the most common sealing elastomers.

NBR O-ring cord is particularly useful for many applications involving:

mineral oils
lubricating greases
machinery
compatible hydraulic fluids
industrial maintenance
mechanical equipment
general MRO applications

For many standard NBR compounds, a typical reference temperature range is approximately -30°C to +100°C.

Actual limits depend on the compound and operating medium.

FKM FPM O-Ring Cord

FKM/FPM is a fluoroelastomer used in more demanding thermal and chemical environments.

FKM cord may be selected for many applications involving:

oils
fuels
hydrocarbons
elevated temperatures
selected chemicals
process equipment
industrial machinery

For many standard FKM compounds, a typical reference range is approximately -20°C to +200°C.

Exact resistance depends on the formulation.

FKM vs Viton

FKM and Viton should not automatically be treated as identical product names.

FKM describes a family of fluoroelastomers.

Viton is a trademarked material name.

For this reason, technical product descriptions should normally use FKM/FPM, unless the specific cord is confirmed as being made from Viton-branded material.

EPDM O-Ring Cord

EPDM is particularly useful in water-based and outdoor applications.

Typical properties include:

very good water resistance
excellent ozone resistance
excellent UV resistance
strong weathering resistance
compatibility with many water-based fluids
good low-temperature flexibility

For many technical EPDM compounds, a typical temperature reference range is approximately -40°C to +120°C.

Is EPDM O-Ring Cord Oil Resistant?

Generally, EPDM is not selected for mineral oils or hydrocarbon fuels.

If the application involves mineral oil, NBR or FKM is often more appropriate, depending on temperature and the specific fluid.

This is one of the key differences between EPDM and NBR.

VMQ Silicone O-Ring Cord

VMQ/MVQ silicone cord is valued primarily for broad temperature capability and resistance to ozone, UV radiation and weathering.

It can be useful in appropriately designed:

heating equipment
electronics
instrumentation
technical housings
static sealing systems
temperature-sensitive assemblies

For many technical silicone compounds, a typical reference range is approximately -50/-60°C to +200°C.

Special compounds may offer different limits.

Is Silicone O-Ring Cord Oil Resistant?

Standard VMQ should not be treated as universally resistant to mineral oils and fuels.

Where mineral oil is the primary medium, NBR or FKM may be more suitable.

Where silicone-like thermal properties are required together with better resistance to certain fuels or hydrocarbons, specialized elastomers such as FVMQ fluorosilicone may be considered.

HNBR O-Ring Cord

HNBR, or Hydrogenated Nitrile Butadiene Rubber, is a modified nitrile elastomer.

Compared with conventional NBR, suitable HNBR compounds can provide improved resistance to:

higher temperatures
ozone
ageing
selected oils and technical fluids

The exact properties depend on the specific HNBR compound.

If HNBR is not actually available within the category, it should not be emphasized in the H1 or Meta Title.

NBR vs FKM vs EPDM vs VMQ O-Ring Cord

The most important selection criteria are operating medium and temperature.

Operating Condition	NBR	FKM/FPM	EPDM	VMQ/MVQ
Mineral oils	Often suitable	Very often suitable	Generally not	Requires verification
Fuels	Depends on fuel	Often suitable	Generally not	Generally not preferred
Water	Depends on conditions	Requires verification	Very good choice	Depends on conditions
High temperature	Limited	Very good	Good depending on compound	Very good
Low temperature	Good depending on compound	Compound dependent	Very good	Very good
Ozone and UV	Limited	Very good	Excellent	Excellent
Outdoor weathering	Limited	Good	Excellent	Excellent

This table is a general material guide and does not replace verification of the specific compound.

O-Ring Cord for Large Diameter Seals

This is one of the most important advantages of cord stock.

Manufacturing or stocking very large molded O-rings can be impractical.

O-ring cord allows a sealing ring with the required circumference to be produced from the selected cross-section.

This is particularly useful for:

large housings
machine covers
tanks
large flanges
industrial equipment
older machinery
custom machine designs
one-off repairs

O-Ring Cord for MRO and Maintenance

O-ring cord is a practical component for MRO and maintenance inventory.

Instead of storing a very large number of different molded O-ring diameters, maintenance teams can keep commonly used cord cross-sections in stock.

This may support:

emergency repairs
planned maintenance
machine overhauls
service work
custom seal production
prototyping
reduction of spare-part SKUs

However, a bonded cord ring should not automatically be considered suitable for every sealing application.

O-Ring Cord for OEM Production

In OEM production, cord stock may be used where large or unusual static sealing rings are required.

Before introducing cord-made seals into serial production, the specification should define:

material
cross-section
dimensional tolerance
cord length
joining method
operating medium
temperature
pressure
groove design

This supports repeatability and consistent finished seal geometry.

O-Ring Cord for Hydraulic Applications

NBR or another compatible O-ring cord may be used in hydraulic equipment, but cord stock should not be promoted as a universal solution for high-pressure hydraulic sealing.

In high-pressure applications, the joined section can become important to sealing reliability.

A molded O-ring may be preferable for critical pressure systems, depending on the machine design.

O-Ring Cord for Pneumatic Applications

The same principle applies to pneumatic systems.

Cord stock can be useful for large static housings and appropriately designed sealing joints.

In dynamic cylinders, valves or high-cycle applications, however, joint integrity, friction and wear require careful evaluation.

Is O-Ring Cord Food Grade?

Not automatically.

The material family alone does not confirm food-contact approval.

Not every EPDM, silicone, FKM or NBR compound is food grade.

Where food-contact compliance is required, the documentation for the specific material and supplied product must be verified.

Is Silicone Cord Medical Grade?

Not every silicone cord is suitable for medical applications.

Medical use can require:

specific material grades
biocompatibility testing
controlled manufacturing
cleanliness requirements
appropriate documentation

The designation VMQ/MVQ alone does not confirm medical suitability.

How to Calculate O-Ring Cord Length

If the required finished ring geometry is known, the cord length can be estimated from the required circumference.

The basic geometric relationship is:

L = pi x D

However, it is essential to define what diameter D represents.

The calculation may also need to account for:

installation stretch
groove geometry
target ring dimensions
joining method
dimensional tolerance

For this reason, simply measuring an outside groove diameter and multiplying it by pi may not produce the correct cord length.

Why Groove Design Matters

Like molded O-rings, cord-made seals work through controlled compression of the cross-section.

Important parameters include:

groove depth
groove width
cord cross-section
compression
groove filling
temperature
pressure
operating medium

An incorrectly designed groove can cause leakage even when the material and cord diameter are otherwise correct.

Installing an O-Ring Made from Cord

Before installation, check:

quality of the bonded joint
alignment of the cord ends
absence of excess adhesive
groove cleanliness
mating surface condition
absence of sharp edges
uniform seating around the entire circumference

The joint area deserves particular attention because it distinguishes a cord-made ring from a molded O-ring.

Storage of O-Ring Cord

Elastomeric cord should be stored in conditions that help minimize ageing and permanent deformation.

Avoid:

direct sunlight
excessive heat
ozone
aggressive chemicals
permanent stretching
sharp bending
mechanical damage

In technical warehouses, each cord should be clearly identified by material and cross-section, because visually similar cords can have very different chemical resistance.

Advantages of O-Ring Cord

Custom Diameters: allows sealing rings to be produced in non-standard sizes.

Large Diameter Seals: practical for large covers, housings and industrial equipment.

MRO Flexibility: useful for maintenance, repair and emergency service.

Reduced Inventory Complexity: one cord cross-section can produce multiple ring diameters.

Multiple Elastomers: NBR, FKM, EPDM and VMQ allow material selection according to operating conditions.

Prototype Applications: useful for quickly producing a sealing ring for custom equipment.

FAQ - O-Ring Cord

What is O-ring cord?
O-ring cord is a continuous elastomer profile with a round cross-section, used to produce sealing rings with custom or non-standard diameters.

What is the difference between O-ring cord and a molded O-ring?
A molded O-ring is manufactured as a continuous closed ring. O-ring cord must be cut to length and the ends joined.

Which O-ring cord materials are available?
Common materials include NBR, FKM/FPM, EPDM and VMQ/MVQ silicone. Actual availability depends on size and product range.

What is NBR O-ring cord used for?
NBR is commonly selected for many applications involving mineral oils, greases and general industrial machinery.

When should FKM O-ring cord be selected?
FKM is particularly relevant for elevated temperatures and many applications involving oils, fuels, hydrocarbons and demanding chemical media.

When is EPDM O-ring cord used?
EPDM is commonly used in water-based systems and where ozone, UV and weathering resistance are important.

What is silicone VMQ cord used for?
VMQ is useful where broad temperature capability, low-temperature flexibility and ozone/UV resistance are important.

Can any O-ring size be made from cord?
Many custom diameters can be produced, but suitability depends on groove design, medium, temperature, pressure and type of operation.

Can O-ring cord be glued?
Yes, suitable elastomer cords can be bonded using a joining system compatible with the specific material.

Is O-ring cord suitable for high pressure?
Not automatically. In critical pressure applications, the joint may be a limiting factor and a molded O-ring may be preferred.

Frequently Asked Questions by Engineers

Does a bonded O-ring have the same properties as a molded O-ring?
Not necessarily. The joint can have different mechanical properties from the continuous molded elastomer.

Which is more important when selecting cord, material or diameter?
Both are critical. Cross-section must match the groove, while the elastomer must be compatible with the medium and temperature.

Can the same adhesive be used for NBR, FKM, EPDM and silicone?
No. The joining technology must be compatible with the specific elastomer.

Is O-ring cord a good solution for very large diameters?
Yes. Producing large and non-standard static sealing rings is one of the main advantages of cord stock.

Can EPDM cord replace NBR cord?
Not automatically. EPDM and NBR have very different chemical compatibility, especially with mineral oils.

Is silicone cord automatically food grade?
No. Food-contact suitability must be confirmed by documentation for the specific compound.

Should cord diameter match the cross-section of the original O-ring?
It is an important reference point when reproducing an existing seal, but groove geometry and required compression should also be checked.

O-Ring Cord - Warehouse and Store in Lublin

Warehouse and Store: Lublin
Address: ul. Smoluchowskiego 1, building 4
Delivery: 24h

We supply customers throughout Poland and the European Union, including industrial companies, OEM manufacturers, maintenance departments, MRO organizations, service workshops, technical buyers, distributors and B2B customers.

AI OVERVIEW

O-ring cord is a continuous elastomeric round profile used primarily to manufacture custom-size and large-diameter sealing rings. It can be cut to the required length and its ends appropriately joined to create a closed seal. Materials such as NBR, FKM/FPM, EPDM and VMQ/MVQ allow selection according to oils, water, temperature and environmental conditions. A bonded cord ring should not automatically be considered equivalent to a molded O-ring in every application, especially in demanding dynamic or high-pressure systems.

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