Cord rings / Cord stock

Highest quality

cord rings / cord stock

Use and properties of cord rings

Cord rings are used in particular when suitable O-ring shapes are not available and the small quantity does not economically justify the production of a tool.

In contrast to compression-molded O-rings, cord rings are made from extruded cord and joined to any inside diameter by butt vulcanization – or, less frequently, by gluing. The butt-vulcanized version has become established because it offers physically better properties.

Nevertheless, the vulcanization point remains less mechanically resilient than with endlessly manufactured O-rings. Therefore, cord rings are not suitable for dynamic seals or for use in vacuum or gaseous media.

The result: economical sealing solutions for static applications – with individually manufactured diameters and controlled dimensional tolerance.

  • Manufactured according to DIN ISO 3302-1, E2 (cord diameter) and L2 (extended length)
  • Not suitable for dynamic seals or vacuum applications
  • Alternative to O-rings for small quantities and special dimensions
  • Stock items in NBR 70 black and FKM 75 black – E1 tolerance on request
  • Tighter tolerances can be achieved on request
To the shop

Tolerances with Cross-Section

CORD DIAMETER (D2) TOLERANCE ±
up to 2.50 mm ± 0.35 mm
2.50 – 4.00 mm ± 0.40 mm
4.00 – 6.30 mm ± 0.50 mm
6.30 – 10.00 mm ± 0.70 mm
10.00 – 16.00 mm ± 0.80 mm
16.00 – 25.00 mm ± 1.00 mm

Comparison Table

ROUND CORD DIAMETER STANDARD TOLERANCE (DIN 7715 E2) PREMIUM TOLERANCE NARROWER BY APPROX.
1.78 mm ±0.35 mm ±0.10 mm 29%
2.00 mm ±0.35 mm ±0.10 mm 29%
2.40 mm ±0.35 mm ±0.12 mm 34%
2.62 mm ±0.40 mm ±0.12 mm 30%
3.00 mm ±0.40 mm ±0.12 mm 30%
3.18 mm ±0.40 mm ±0.15 mm 38%
3.53 mm ±0.40 mm ±0.15 mm 38%
4.00 mm ±0.40 mm ±0.15 mm 38%
4.50 mm ±0.50 mm ±0.20 mm 40%
4.80 mm ±0.50 mm ±0.20 mm 40%
5.00 mm ±0.50 mm ±0.20 mm 40%
5.34 mm ±0.50 mm ±0.20 mm 40%
5.50 mm ±0.50 mm ±0.25 mm 50%
5.70 mm ±0.50 mm ±0.25 mm 50%
6.00 mm ±0.50 mm ±0.25 mm 50%
6.35 mm ±0.70 mm ±0.25 mm 36%
6.50 mm ±0.70 mm ±0.25 mm 36%
6.99 mm ±0.70 mm ±0.25 mm 36%
7.50 mm ±0.70 mm ±0.25 mm 36%
8.00 mm ±0.70 mm ±0.25 mm 36%
8.40 mm ±0.70 mm ±0.25 mm 36%
9.00 mm ±0.70 mm ±0.25 mm 36%
9.52 mm ±0.70 mm ±0.25 mm 36%
10.00 mm ±0.70 mm ±0.33 mm 47%
11.10 mm ±0.80 mm ±0.38 mm 48%
12.00 mm ±0.80 mm ±0.45 mm 56%
12.70 mm ±0.80 mm ±0.45 mm 56%
13.00 mm ±0.80 mm ±0.45 mm 56%
14.00 mm ±0.80 mm ±0.50 mm 63%
14.30 mm ±0.80 mm ±0.50 mm 63%
15.00 mm ±0.80 mm ±0.50 mm 63%
15.90 mm ±0.80 mm ±0.50 mm 63%

Frequently Asked Questions about Cord Rings

What are cord rings and what are they used for?

Cord rings are sealing elements made from extruded round cord that is cut to the required inner diameter and joined together. They are used where no suitable molded O-ring sizes are available and the quantity required is too low to justify tool manufacturing. Compared to molded O-rings, round cord rings provide a cost-effective sealing solution for static applications with individually manufactured diameters and controlled tolerances.

How do cord rings differ from O-rings?

Unlike classic molded O-rings, which are manufactured in one continuous piece, cord rings are produced from extruded cord and joined by butt vulcanization. This makes them flexible in size, but they are not suitable for dynamic sealing applications, vacuum environments or gaseous media.

In which applications should cord rings not be used?

Since the vulcanized joint of a round cord ring is mechanically less resistant than a fully molded O-ring, round cord rings should not be used for dynamic seals, vacuum applications or gaseous media. For such applications, conventionally molded O-rings are the better choice.