M8 SEMS Screws with Captive Conical Spring Washers dimensions to DIN 6900-5 Z9 and DIN 6908: 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.
The M8 size of SEMS Screws with Captive Conical Spring Washers is dimensioned by DIN 6900-5 Z9 and DIN 6908. The tables below give the dimensional row from the standard, the drill and spanner sizes that go with it, and the assembly torque per property class. The technical drawing on this page redraws to the exact values selected.
M8 Dimensional Row (DIN 6900-5 Z9 and DIN 6908)
| Thread size | Pitch (mm) | Washer inside diameter (mm) | Washer outside diameter (mm) | Washer thickness (mm) | Material options | Reference standard |
|---|
| M8 | 1.25 | 7.4~7.55 | 17.57~18.0 | 2.0 | steel or A2 stainless | DIN 6900-5 Z9 and DIN 6908 |
Spanner & Drive for M8 SEMS Screws with Captive Conical Spring Washers
Drive geometry for M8 SEMS Screws with Captive Conical Spring 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.
Installation Tips for M8 SEMS Screws with Captive Conical Spring 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.
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 Conical Spring Washers
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
-
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.
-
Appliances
High-volume assembly with a washer that cannot fall away from the screw.
-
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
