DIN 6908 specifies the dimensions and tolerances for sems screws with captive conical spring washers. The full dimensional table is reproduced below, followed by the DIN, ISO and ASME parts that match or supersede it.
- Standard
- DIN 6908
- Product
- SEMS Screws with Captive Conical Spring Washers
- Governing standards
- DIN 6900-5 Z9 and DIN 6908
Equivalence between national standards is dimensional, not always metallurgical. Check the property class separately when substituting.
DIN 6908 covers the dimensional requirements for sems screws with captive conical spring washers. Reproduced below: the complete size table, the tolerance grades, and the companion and equivalent standards referenced when ordering to this document.
DIN 6908 — Scope
DIN 6908 specifies the dimensions and tolerances of sems screws with captive conical spring washers. Material, property class, surface finish and packaging are governed by separate documents in the same standards family (for example ISO 898-1 for the mechanical property classes of bolts and screws).
Tolerance & Product Grades
DIN 6908, alongside the related DIN 6900-5 Z9 and DIN 6908 entries on this site, specifies product grades (typically A or B for fine work and C for general engineering) and tolerance classes for the controlling dimensions. Choose the grade against the precision your application requires.
Dimensions Specified by DIN 6908
| Thread size | Pitch (mm) | Washer inside diameter (mm) | Washer outside diameter (mm) | Washer thickness (mm) | Material options | Reference standard |
|---|
| M2.5 | 0.45 | 2.25~2.35 | 5.7~6.0 | 0.5 | steel or A2 stainless | DIN 6900-5 Z9 and DIN 6908 |
| M3 | 0.5 | 2.75~2.85 | 6.64~7.0 | 0.6 | steel or A2 stainless | DIN 6900-5 Z9 and DIN 6908 |
| M4 | 0.7 | 3.6~3.72 | 8.64~9.0 | 1.0 | steel or A2 stainless | DIN 6900-5 Z9 and DIN 6908 |
| M5 | 0.8 | 4.55~4.67 | 10.57~11.0 | 1.2 | steel or A2 stainless | DIN 6900-5 Z9 and DIN 6908 |
| M6 | 1.0 | 5.5~5.62 | 13.57~14.0 | 1.5 | steel or A2 stainless | DIN 6900-5 Z9 and DIN 6908 |
| M8 | 1.25 | 7.4~7.55 | 17.57~18.0 | 2.0 | steel or A2 stainless | DIN 6900-5 Z9 and DIN 6908 |
| M10 | 1.5 | 9.3~9.45 | 22.48~23.0 | 2.5 | steel or A2 stainless | DIN 6900-5 Z9 and DIN 6908 |
| M12 | 1.75 | 11.0~11.18 | 28.48~29.0 | 3.0 | steel or A2 stainless | DIN 6900-5 Z9 and DIN 6908 |
Equivalent Standards
Where direct equivalents exist (ISO ↔ DIN, ISO ↔ ASME), they are listed on the parent SEMS Screws with Captive Conical Spring Washers page. Always confirm against the dimensions on this page, since some "equivalent" standards differ in tolerances and head geometry.
When to Specify DIN 6908
DIN 6908 is still widely used in European mechanical engineering and as a cross-reference on legacy drawings; its ISO equivalent is preferred for new designs.
Applications & Industries
SEMS Screws with Captive Conical Spring Washers are bought for a small number of well-defined jobs. These are the ones we ship them for. Stocked from M2.5 to M12.
Industries that specify SEMS Screws with Captive Conical Spring Washers
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Instrument housings
Small fasteners where repeated cover removal must not lose the washer.
-
Control panels
Captive spring-washer screws on covers and electrical equipment.
-
Light machinery
Joints that settle slightly during service and need maintained contact.
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Appliances
High-volume assembly with a washer that cannot fall away from the screw.
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Food, pharma & cleanroom
Stainless assemblies that are washed down, where the finish matters as much as the strength.
-
Machine building & OEM
The default fastener on production equipment: covers, brackets, motor mounts and sub-assemblies tightened to a specified torque.
Typical applications
- selecting the washer inside diameter, outside diameter and thickness together
- combining a machine screw with a captive conical spring washer
- using limited spring travel to maintain light joint contact
- keeping the washer attached during panel and cover service
- joints where the property class is stated on the drawing
- clamping two machined faces to a calculated preload
Service conditions to specify against
- Marine and coastal
- Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
- High load
- Supplied in ISO 898-1 property classes, so the joint can be designed to a stated proof load and tightened to a calculated torque rather than by feel.
- Torque and preload
- The joint is designed around bolt tension, so lubrication, coating and the friction coefficient all change the torque figure — state them together.
Where to use something else
- Do not use the conical spring washer as a structural flat washer or as a wedge-lock pair.
- Do not use a machine thread into unthreaded sheet or timber; use a tapping screw, rivet nut or insert made for that parent material.
Full application guide: where SEMS Screws with Captive Conical Spring Washers are used, how to specify them, and the cases they are wrong for
