ISO 10644 specifies the dimensions and tolerances for sems screws with captive flat washers. The full dimensional table is reproduced below, followed by the DIN, ISO and ASME parts that match or supersede it.
- Standard
- ISO 10644
- Product
- SEMS Screws with Captive Flat Washers
- Governing standards
- DIN 7985 / ISO 7045 and EN ISO 10644
Equivalence between national standards is dimensional, not always metallurgical. Check the property class separately when substituting.
ISO 10644 covers the dimensional requirements for sems screws with captive flat washers. Reproduced below: the complete size table, the tolerance grades, and the companion and equivalent standards referenced when ordering to this document.
ISO 10644 — Scope
ISO 10644 specifies the dimensions and tolerances of sems screws with captive flat 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
ISO 10644, alongside the related DIN 7985 / ISO 7045 and EN ISO 10644 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 ISO 10644
| Thread size | Pitch (mm) | Washer outside diameter (mm) | Washer thickness (mm) | Property/material options | Drive | Reference standard |
|---|
| M2.5 | 0.45 | 6 | 0.6 | steel 4.8/8.8 or A2 stainless | Phillips | DIN 7985 / ISO 7045 and EN ISO 10644 |
| M3 | 0.5 | 7 | 0.6 | steel 4.8/8.8 or A2 stainless | Phillips | DIN 7985 / ISO 7045 and EN ISO 10644 |
| M4 | 0.7 | 9 | 0.8 | steel 4.8/8.8 or A2 stainless | Phillips | DIN 7985 / ISO 7045 and EN ISO 10644 |
| M5 | 0.8 | 10 | 1.0 | steel 4.8/8.8 or A2 stainless | Phillips | DIN 7985 / ISO 7045 and EN ISO 10644 |
| M6 | 1.0 | 12 | 1.6 | steel 4.8/8.8 or A2 stainless | Phillips | DIN 7985 / ISO 7045 and EN ISO 10644 |
| M8 | 1.25 | 16 | 2.0 | steel 4.8/8.8 or A2 stainless | Phillips | DIN 7985 / ISO 7045 and EN ISO 10644 |
Equivalent Standards
Where direct equivalents exist (ISO ↔ DIN, ISO ↔ ASME), they are listed on the parent SEMS Screws with Captive Flat Washers page. Always confirm against the dimensions on this page, since some "equivalent" standards differ in tolerances and head geometry.
Companion Standards
ISO 10644 controls only the geometry of sems screws with captive flat washers. The mechanical strength is set by ISO 898-1 (bolts and screws) or ISO 898-2 (nuts); the surface finish is governed by separate finish standards (e.g. ISO 4042 for electroplating). For corrosion testing, the relevant document is ISO 9227 (neutral salt spray).
Applications & Industries
Where SEMS Screws with Captive Flat Washers are used, and what decides the specification in each case. Stocked from M2.5 to M8.
Industries that specify SEMS Screws with Captive Flat Washers
-
Electrical assembly
Captive flat-washer screws for panels, terminals and equipment covers.
-
Appliance production
High-volume screwdriving where a separate washer would slow assembly.
-
Sheet-metal enclosures
Removable covers that must retain the washer on the screw.
-
Machine guarding
Service hardware that stays with the cover during removal.
-
Steel fabrication
Bolted connections in frames, enclosures, walkways and weldments, on the bench and on site.
-
Energy & infrastructure
Tower, pipework, switchgear and plant fixings specified for long service life and inspectable joints.
Typical applications
- combining the screw and flat washer into one captive assembly
- spreading bearing load while preventing washer loss during service
- using a Phillips drive for controlled production installation
- selecting the washer outside diameter and thickness with the thread size
- clamping two machined faces to a calculated preload
- bolting brackets, motors and gearboxes to a frame
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 substitute the captive washer for a hardened structural washer in a high-preload joint.
- 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 Flat Washers are used, how to specify them, and the cases they are wrong for
