M2.5 SEMS Screws with Captive Flat Washers (DIN 7985 / ISO 7045 and EN ISO 10644) are specified by thread size, length and head dimensions. The M2.5 row from the standard is reproduced below, followed by the drill sizes, spanner size and torque values used when installing this size.
M2.5 Dimensional Row (DIN 7985 / ISO 7045 and EN 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 |
Spanner & Drive for M2.5 SEMS Screws with Captive Flat Washers
Drive geometry for M2.5 SEMS Screws with Captive Flat Washers is given by the row above; match the tool to the listed values.
Installation Tips for M2.5 SEMS Screws with Captive Flat Washers
- Pozidriv (PZ) drivers ride out of Phillips (PH) recesses and vice versa — confirm the recess marking on the head before assembly.
- For automated assembly, an ACR (Anti-Cam-Out Ribs) or torx-equivalent driver gives noticeably longer bit life than plain PH.
- At M2.5 the joint is sensitive to over-torque — use a torque-limiting driver and check the head doesn't bury into a softer counterpart.
Mating Parts for M2.5
For M2.5, pair with a M2.5 hex nut (ISO 4032 / DIN 934) and, where used, a M2.5 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
Applications & Industries for M2.5 SEMS Screws with Captive Flat Washers
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
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Electrical assembly
Captive flat-washer screws for panels, terminals and equipment covers.
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Appliance production
High-volume screwdriving where a separate washer would slow assembly.
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Sheet-metal enclosures
Removable covers that must retain the washer on the screw.
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Machine guarding
Service hardware that stays with the cover during removal.
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Steel fabrication
Bolted connections in frames, enclosures, walkways and weldments, on the bench and on site.
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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
