Property Class 8.8 Steel SEMS Screws with Captive Conical Spring Washers are supplied to ISO 898-1 property class 8.8. Corrosion behaviour is requires plating (zinc) for corrosion protection, the material is magnetic, and the usable service range is commonly limited to approx. +300 °C; confirm against the coating and the load. In practice this grade is the workhorse medium-carbon alloy class for structural joints.
- Grade
- ISO 898-1 property class 8.8
- Corrosion resistance
- Requires plating (zinc) for corrosion protection
- Magnetic response
- Magnetic
- Service temperature
- commonly limited to approx. +300 °C; confirm against the coating and the load
Property values are typical for the grade. Certified mechanical test data is available on request for production orders.
SEMS Screws with Captive Conical Spring Washers manufactured in Property Class 8.8 Steel (ISO 898-1 property class 8.8) are dimensioned to DIN 6900-5 Z9 and DIN 6908. The sections below give the mechanical and physical properties of the grade, its behavior in corrosive and elevated-temperature service, and the full size table.
Why Choose Property Class 8.8 Steel for SEMS Screws with Captive Conical Spring Washers
The workhorse medium-carbon alloy class for structural joints. For sems screws with captive conical spring washers, this matters when requires plating (zinc) for corrosion protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 898-1 property class 8.8 |
|---|
| Magnetic response | Magnetic |
|---|
| Service temperature | commonly limited to approx. +300 °C; confirm against the coating and the load |
|---|
| Corrosion characteristic | Requires plating (zinc) for corrosion protection |
|---|
Corrosion Behavior in Service
Carbon and alloy steel sems screws with captive conical spring washers require a coating for corrosion protection. Zinc plating (with or without passivation) is the most common; hot-dip galvanizing is used for outdoor structural service; black-oxide is mainly a tarnish-prevention finish for tool-room use.
Comparable Grades
For SEMS Screws with Captive Conical Spring Washers, class 10.9 or 12.9 is the comparable strength step. Move up when the joint preload approaches the proof load of the current class; move down when the joint is over-specified. For corrosion-critical service, switch to stainless A2 or A4.
Sizes of SEMS Screws with Captive Conical Spring Washers Available in Property Class 8.8 Steel
| 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 |
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.
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Control panels
Captive spring-washer screws on covers and electrical equipment.
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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.
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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
