SMS 1588 is the Swedish national standard for metric O-ring dimensions. It is the reference specification used throughout Scandinavia and the Baltic region for hydraulic systems, pumps, valves, marine equipment, pulp-and-paper machinery, and general industrial sealing. If you are sourcing seals for a Swedish, Finnish, or Danish OEM drawing, you will almost certainly encounter an SMS 1588 callout.
This guide explains the structure of SMS 1588, how its metric sizes are organized, the tolerances you should expect, groove design, and how SMS 1588 maps to AS568 and ISO 3601.
Short Answer: SMS 1588 at a Glance
| Attribute | Detail |
|---|---|
| Standard | SMS 1588 — Swedish metric O-ring dimensions |
| Units | Millimetres (inside diameter × cross section) |
| Cross sections | 1.00 mm to 8.00 mm |
| Common series | 1.00, 1.50, 1.80, 2.00, 2.50, 2.65, 3.00, 3.55, 4.00, 5.00, 5.30, 6.00, 7.00, 8.00 mm |
| Tolerance bands | Cross-section ±0.08 to ±0.18 mm; ID ±0.14 to ±0.56 mm depending on size |
| Main markets | Sweden, Finland, Denmark, Norway, Baltic states |
| Closest relatives | DIN 3771, ISO 3601 A/B/C/D/E, BS 4518, JIS B 2401 |
| Inch equivalent | AS568 cross sections convert to nearest metric SMS sizes |
SMS 1588 does not specify material or hardness — only dimensions and tolerances. The design engineer adds the elastomer callout separately, usually NBR, FKM, EPDM, HNBR, or VMQ.
What Is SMS 1588?
SMS 1588 is published by the Swedish Standards Institute (SIS). It defines inside diameters and cross-sectional diameters in millimetres, with tolerance bands for both dimensions. The standard is deliberately aligned with DIN 3771 and ISO 3601-1, so manufacturers often cover all three with the same tooling.
Key points:
- SMS 1588 specifies dimensions and tolerances only, not material.
- Sizes are quoted as ID × CS in millimetres (for example, 25.00 × 3.55 mm).
- Most sizes have direct or near-direct equivalents in ISO 3601-1 and DIN 3771.
Parts and Structure of SMS 1588
An SMS 1588 specification is typically written as:
> SMS 1588 — 25.00 × 3.55 mm — FKM 75 Shore A
This means standard SMS 1588, 25.00 mm inside diameter, 3.55 mm cross section, and FKM 75 Shore A material. Unlike AS568 dash numbers, SMS 1588 uses direct metric dimensions, eliminating inch-to-metric ambiguity.
The standard is organised around cross-sectional diameter series. Once the cross section is selected, a range of inside diameters is available within that series. Engineers usually select the smallest cross section that gives adequate squeeze and pressure capacity for the gland, then pick the ID that matches the bore or shaft diameter.
SMS 1588 Cross-Section Series
The cross section determines squeeze, pressure capability, groove width, and compression set. SMS 1588 includes cross sections from 1.00 mm to 8.00 mm.
The table below lists the standard SMS 1588 cross sections and their typical applications.
| Cross Section (mm) | Typical Application | Notes |
|---|---|---|
| 1.00 | Precision equipment, instrumentation | Smallest standard cross section |
| 1.50 | Small hydraulic and pneumatic fittings | Compact static and dynamic seals |
| 1.60 | Industrial sensors, valves | Common in instrumentation |
| 1.78 | Compatible with AS568-004 cross section | Near 1.80 mm ISO/DIN size |
| 1.80 | Equivalent to ISO 3601 A-series / DIN 3771 A | Very common in compact fittings |
| 2.00 | General-purpose static seals | Versatile medium-size cross section |
| 2.40 | Medium-pressure fluid systems | Used in pumps and process equipment |
| 2.50 | Pumps and process equipment | Popular Scandinavian size |
| 2.62 | Compatible with AS568-1xx cross section | Near 2.65 mm ISO/DIN size |
| 2.65 | Equivalent to ISO 3601 B-series / DIN 3771 B | Common hydraulic series |
| 3.00 | Heavy-duty hydraulic applications | Higher pressure capacity |
| 3.53 | Compatible with AS568-2xx cross section | Near 3.55 mm ISO/DIN size |
| 3.55 | Equivalent to ISO 3601 C-series / DIN 3771 C | Most common heavy-duty series |
| 4.00 | Large bore flanges, static seals | Static flange applications |
| 5.00 | High-pressure hydraulics | Heavy equipment |
| 5.30 | Equivalent to ISO 3601 D-series | Large bore hydraulics |
| 5.33 | Compatible with AS568-3xx cross section | Near 5.30 mm ISO/DIN size |
| 6.00 | Marine and offshore equipment | Large-diameter seals |
| 6.99 | Compatible with AS568-4xx cross section | Near 7.00 mm ISO/DIN size |
| 7.00 | Equivalent to ISO 3601 E-series | Large industrial tanks |
| 8.00 | Specialised heavy static sealing | Largest standard cross section |
Several SMS 1588 cross sections match AS568 inch equivalents:
- 1.78 mm ≈ 0.070 in (AS568-004 base cross section)
- 2.62 mm ≈ 0.103 in (AS568-1xx series)
- 3.53 mm ≈ 0.139 in (AS568-2xx series)
- 5.33 mm ≈ 0.210 in (AS568-3xx series)
- 6.99 mm ≈ 0.275 in (AS568-4xx series)
This makes cross-referencing between SMS 1588 and AS568 straightforward for most common sizes.
SMS 1588 Dimensional Tolerances
SMS 1588 specifies absolute tolerance bands in millimetres for inside diameter and cross section. Tolerances increase with size, matching AS568 and ISO 3601-1.
SMS 1588 Tolerance Table
| Cross Section (mm) | CS Tolerance | ID Range (mm) | ID Tolerance |
|---|---|---|---|
| 1.00 – 1.60 | ±0.08 | ≤ 10 | ±0.14 |
| 1.00 – 1.60 | ±0.08 | 10 – 20 | ±0.17 |
| 1.78 – 2.65 | ±0.09 | ≤ 13 | ±0.17 |
| 1.78 – 2.65 | ±0.09 | 13 – 30 | ±0.22 |
| 1.78 – 2.65 | ±0.09 | 30 – 50 | ±0.28 |
| 3.00 – 3.55 | ±0.10 | ≤ 20 | ±0.20 |
| 3.00 – 3.55 | ±0.10 | 20 – 40 | ±0.28 |
| 3.00 – 3.55 | ±0.10 | 40 – 85 | ±0.36 |
| 4.00 – 5.33 | ±0.13 | ≤ 40 | ±0.28 |
| 4.00 – 5.33 | ±0.13 | 40 – 80 | ±0.36 |
| 4.00 – 5.33 | ±0.13 | 80 – 140 | ±0.45 |
| 6.00 – 7.00 | ±0.15 | ≤ 80 | ±0.36 |
| 6.00 – 7.00 | ±0.15 | 80 – 160 | ±0.45 |
| 8.00 | ±0.18 | ≤ 120 | ±0.45 |
| 8.00 | ±0.18 | 120 – 250 | ±0.56 |
How to read the table: a 25.00 × 3.55 mm O-ring has CS tolerance ±0.10 mm and ID tolerance ±0.28 mm because the 25 mm ID falls in the 20–40 mm range for the 3.00–3.55 mm cross-section band. For precision work, tighter tolerances can be agreed to ISO 3601-1 Grade S or drawing tolerances.
Groove Design for SMS 1588 O-Rings
Good sealing depends on the gland as much as the O-ring. SMS 1588 gives the O-ring dimensions; the groove must be designed separately to achieve the correct squeeze, fill ratio, and clearance.
Static Grooves
For static face or radial seals, target 15–25% compression. Groove width ≈ 1.15 × CS. Static grooves tolerate higher squeeze than dynamic grooves because friction and wear are not concerns.
Dynamic Grooves
For reciprocating hydraulic or pneumatic cylinders, target 10–15% compression. Groove width ≈ 1.2–1.3 × CS to reduce friction and prevent rolling.
Rotary Grooves
Limit groove fill to 75–80% maximum. Use harder elastomer grades (80–90 Shore A) and heat-resistant materials such as FKM or HNBR. High surface speeds may need PTFE-coated or spring-energised solutions.
Quick Groove Design Summary
| Seal Type | Groove Width | Target Compression | Notes |
|---|---|---|---|
| Static (face/radial) | ≈ 1.15 × CS | 15–25% | Higher squeeze improves sealing |
| Dynamic (reciprocating) | ≈ 1.2–1.3 × CS | 10–15% | Balance seal and friction |
| Rotary | ≈ 1.2 × CS | 8–12% | Use hard, heat-resistant material |
Use our compression calculator to verify squeeze percentage.
SMS 1588 vs AS568 and ISO 3601-1
SMS 1588 overlaps heavily with other metric standards. The table below summarises how it relates to the main global O-ring standards.
| Standard | Region | Relationship to SMS 1588 |
|---|---|---|
| DIN 3771 | Germany / EU | Cross sections and ID ranges closely aligned with SMS 1588 |
| ISO 3601-1 | International | A/B/C/D/E series map directly to SMS 1588 dimensions |
| BS 4518 | UK | British metric sizes share the same cross sections |
| JIS B 2401 | Japan | P/G/S/V series are metric-compatible with SMS 1588 |
| AS568 | USA | Imperial cross sections convert to nearest metric SMS sizes |
SMS 1588 to AS568 Cross-Reference
The table below shows common SMS 1588 to AS568 cross-references.
| SMS 1588 Size (ID × CS mm) | Approximate AS568 Dash | AS568 Dimensions (inch) | Notes |
|---|---|---|---|
| 1.78 × 1.78 mm | −006 | 0.070 × 0.070 in | Nearly identical after unit conversion |
| 9.25 × 1.78 mm | −112 | 0.487 × 0.103 in | AS568 CS 2.62 mm vs SMS 2.65 mm |
| 12.37 × 2.62 mm | −112 | 0.487 × 0.103 in | Direct CS match (2.62 mm) |
| 18.77 × 3.53 mm | −210 | 0.734 × 0.139 in | Direct CS match (3.53 mm) |
| 25.00 × 3.55 mm | −214 | 0.984 × 0.139 in | 0.01 mm ID difference from ISO |
| 37.47 × 5.33 mm | −309 | 1.475 × 0.210 in | Direct CS match (5.33 mm) |
| 113.67 × 6.99 mm | −425 | 4.475 × 0.275 in | Direct CS match (6.99 mm) |
| 659.77 × 6.99 mm | −932 | 25.975 × 0.275 in | Largest standard size |
For most industrial applications, differences under 0.5 mm are acceptable, but always verify gland dimensions and squeeze. Compare standards on the SMS 1588, AS568, and ISO 3601 pages.
Common SMS 1588 Size Examples
The table below shows representative SMS 1588 sizes across the standard range.
| Inside Diameter (mm) | Cross Section (mm) | Typical Application |
|---|---|---|
| 3.00 | 1.00 | Precision instruments |
| 5.00 | 1.50 | Small pneumatic couplings |
| 7.00 | 1.80 | Compact hydraulic fittings |
| 10.00 | 2.00 | General machinery seals |
| 15.00 | 2.50 | Pump and valve housings |
| 20.00 | 2.65 | Hydraulic cylinders |
| 25.00 | 3.00 | Medium-pressure systems |
| 30.00 | 3.55 | Industrial flange seals |
| 40.00 | 4.00 | Large static seals |
| 50.00 | 5.00 | Heavy equipment hydraulics |
| 80.00 | 5.30 | Large bore hydraulics |
| 100.00 | 6.00 | Marine and offshore |
| 150.00 | 7.00 | Large industrial tanks |
| 200.00 | 8.00 | Specialised static sealing |
SMS 1588 covers many more ID × CS combinations within each cross-section series.
Material Selection for SMS 1588 O-Rings
Material is selected based on fluid compatibility, temperature, pressure, and movement. Common choices include:
| Material | Hardness | Typical Application |
|---|---|---|
| NBR | 70–90 Shore A | Hydraulic oil, fuel, general industrial |
| HNBR | 70–90 Shore A | Elevated temperature, ozone, sour gas |
| FKM | 75–90 Shore A | High temperature, aggressive chemicals, fuel |
| EPDM | 70–80 Shore A | Water, steam, phosphate ester fluids |
| VMQ (silicone) | 60–70 Shore A | Low temperature, food-grade, medical |
| PTFE | N/A | Chemical resistance, spring-energised seals |
For marine and offshore applications, consider HNBR or premium FKM. For food-contact or pharmaceutical equipment, use platinum-cured VMQ with appropriate certification.
Inspection and Acceptance Criteria
SMS 1588-conforming O-rings should be inspected for dimensions and visual quality:
Dimensional inspection: measure ID with optical comparator or video system; measure CS at three points; compare against SMS 1588 tolerance bands.
Visual inspection: check for cracks, voids, porosity, or foreign inclusions; verify flash is within agreed limits.
Batch testing (critical): hardness, tensile/elongation, compression set, and fluid swell per ASTM or ISO methods. Request a CoC or material test report when traceability is required.
FAQ
Q1: What is SMS 1588?
SMS 1588 is the Swedish national standard for metric O-ring dimensions. It defines inside diameters and cross sections in millimetres, with tolerance bands for both. It is widely used in Sweden, Finland, Denmark, Norway, and Baltic industrial markets.
Q2: Is SMS 1588 the same as DIN 3771?
They are very similar but not identical. Most cross sections and size ranges overlap, making them interchangeable in many applications, but always verify exact dimensions on the drawing.
Q3: What industries use SMS 1588 O-rings?
SMS 1588 is commonly used in Scandinavian manufacturing, shipbuilding, pulp and paper, hydropower, offshore oil and gas, agricultural machinery, and automotive suppliers serving Nordic OEMs.
Q4: How do I convert SMS 1588 sizes to AS568?
Convert the metric ID and CS to inches, then find the nearest AS568 dash number. For example, 25.00 × 3.55 mm converts to approximately 0.984 × 0.140 in, which is close to AS568-214 (0.984 × 0.139 in). For precision applications, verify tolerances and gland fit rather than relying on approximate conversion.
Q5: What tolerances does SMS 1588 specify?
Cross-section tolerances range from ±0.08 mm for small cross sections to ±0.18 mm for 8.00 mm cross sections. ID tolerances range from ±0.14 mm for small IDs to ±0.56 mm for large IDs. The exact tolerance depends on both the cross-section size and the ID range.
Q6: What groove width should I use for an SMS 1588 O-ring?
For static seals, use approximately 1.15 × CS. For dynamic reciprocating seals, use 1.2–1.3 × CS. For rotary seals, limit groove fill to 75–80% and use harder, heat-resistant materials.
Q7: Can you supply SMS 1588 O-rings with material certifications?
Yes. We provide batch certificates, material test reports, and traceability for NBR, FKM, EPDM, HNBR, and silicone SMS 1588 O-rings.
Q8: Do you stock SMS 1588 sizes or manufacture to order?
We manufacture SMS 1588 O-rings to order with no tooling charge for standard cross sections. Custom sizes and special compounds are available with MOQ starting at 1 piece, making it economical for prototypes and low-volume production.
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Need SMS 1588 O-rings for a Swedish or Scandinavian project? Request a quote with the size (ID × CS), material, hardness, quantity, and any certification requirements. Our engineering team can also cross-reference SMS 1588 to AS568 or ISO 3601-1 and recommend the right groove design for your application. Contact us for technical support or fast samples.