Metric O-Rings (ISO 3601) manufactured in FKM (Viton®-type) (fluoroelastomer, typically 75 Shore A) are dimensioned to ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections). The sections below give the mechanical and physical properties of the grade, its behavior in corrosive and elevated-temperature service, and the full size table.
Why Choose FKM (Viton®-type) for Metric O-Rings (ISO 3601)
Specified where temperature or chemical exposure exceeds nitrile. For metric o-rings (iso 3601), this matters when excellent resistance to heat, fuels, and most chemicals; poor with ketones and hot water/steam is the primary requirement.
Mechanical & Physical Properties
| Grade designation | fluoroelastomer, typically 75 Shore A |
|---|---|
| Magnetic response | Non-magnetic |
| Service temperature | approx. -20 °C to +200 °C |
| Corrosion characteristic | Excellent resistance to heat, fuels, and most chemicals; poor with ketones and hot water/steam |
Corrosion Behavior in Service
Carbon and alloy steel metric o-rings (iso 3601) require a coating for corrosion protection. Zinc plating (with or without passivation) is the most common; hot-dip galvanizing is used for outdoor structural service; black-oxide is mainly a tarnish-prevention finish for tool-room use.
Comparable Grades
For metric o-rings (iso 3601), consider NBR where the service is ordinary mineral oil and the cost matters, or EPDM for hot water and steam, which attacks FKM. Elastomer selection is decided by the medium, the temperature range and whether the seal is static or dynamic — not by strength.
Sizes of Metric O-Rings (ISO 3601) Available in FKM (Viton®-type)
| Cross-section (mm) | Typical inside-diameter range (mm) | Common compounds | Notes |
|---|---|---|---|
| 1.0 | 1.0 – 20 | NBR, FKM, EPDM, silicone | miniature and pneumatic |
| 1.5 | 2.0 – 40 | NBR, FKM, EPDM, silicone | small pneumatic and instrument |
| 1.78 | 1.78 – 50 | NBR, FKM, EPDM | nearest metric equivalent to the 1/16 in section |
| 2.0 | 3.0 – 100 | NBR, FKM, EPDM, silicone | general hydraulic and pneumatic |
| 2.5 | 5.0 – 150 | NBR, FKM, EPDM | general hydraulic |
| 3.0 | 6.0 – 200 | NBR, FKM, EPDM | general hydraulic |
| 3.5 | 10 – 250 | NBR, FKM | hydraulic |
| 4.0 | 12 – 300 | NBR, FKM | hydraulic and larger flanges |
| 5.0 | 20 – 400 | NBR, FKM | large flanges and covers |
| 5.33 | 20 – 400 | NBR, FKM | nearest metric equivalent to the 3/16 in section |
| 6.0 | 25 – 500 | NBR, FKM | large covers and housings |
Dimensions are independent of the material: every size above is available in FKM (Viton®-type).
Custom manufacturing · Made to drawing
Need this seal in a grade that is not listed?
Fkm is one of the grades the catalog describes. Inside diameter, cross-section and compound are the three that matter, and the compound is chosen against the fluid and the temperature rather than the dimensions.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
