M8 SEMS Screws with Captive Flat Washers dimensions to DIN 7985 / ISO 7045 and EN ISO 10644: coarse thread pitch 1.25 mm, clearance hole (ISO 273 medium) 9 mm, tapping drill 6.8 mm. Tighten to approximately 25 Nm at property class 8.8 in a dry, as-supplied condition.
- Coarse thread pitch
- 1.25 mm
- Clearance hole (ISO 273 medium)
- 9 mm
- Tapping drill
- 6.8 mm
- Tightening torque (class 8.8)
- 25 Nm
Figures are nominal values from the governing standard. Confirm against the tolerance class for your application before machining or ordering.
M8 SEMS Screws with Captive Flat Washers (DIN 7985 / ISO 7045 and EN ISO 10644) are specified by thread size, length and head dimensions. The M8 row from the standard is reproduced below, followed by the drill sizes, spanner size and torque values used when installing this size.
M8 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 |
|---|
| M8 | 1.25 | 16 | 2.0 | steel 4.8/8.8 or A2 stainless | Phillips | DIN 7985 / ISO 7045 and EN ISO 10644 |
Spanner & Drive for M8 SEMS Screws with Captive Flat Washers
Drive geometry for M8 SEMS Screws with Captive Flat Washers is given by the row above; match the tool to the listed values.
Hole Sizes for M8
| Coarse-thread pitch (ISO 724) | 1.25 mm |
|---|
| Through-hole / clearance (ISO 273 medium) | 9 mm |
|---|
| Tapping drill, coarse thread | 6.8 mm |
|---|
Tightening Torque for M8
| Class 8.8 (dry, ~µ 0.125) | ≈ 25 Nm |
|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 35 Nm |
|---|
| Class 12.9 (dry, ~µ 0.125) | ≈ 41 Nm |
|---|
Indicative dry-joint values. Lubrication can lower the required torque by 15–25%. Always confirm against the joint design, especially when going up a strength class.
Proof Load & Strength for M8
| Tensile stress area As (ISO 898-1) | 36.6 mm² |
|---|
| Proof load, class 8.8 | 21 kN |
|---|
| Proof load, class 10.9 | 30 kN |
|---|
| Proof load, class 12.9 | 36 kN |
|---|
| Min. ultimate tensile, class 8.8 | 29 kN |
|---|
Proof load = stress area × proof stress per ISO 898-1. Design joints so the working preload stays below the proof load of the selected class.
Mating Parts for M8
For M8, pair with a M8 hex nut (ISO 4032 / DIN 934) and, where used, a M8 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
When to Step Up or Down from M8
When the joint preload approaches the proof load of M8 class 8.8, step up to M10 class 8.8 (or move to M8 class 10.9). When the joint is over-specified, M6 often saves weight and cost without losing the safety margin.
Applications & Industries for M8 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
-
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
