Property Class 8.8 Steel SEMS Screws with Captive Flat 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 Flat Washers manufactured in Property Class 8.8 Steel (ISO 898-1 property class 8.8) are dimensioned to DIN 7985 / ISO 7045 and EN ISO 10644. 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 Flat Washers
The workhorse medium-carbon alloy class for structural joints. For sems screws with captive flat 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 flat 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 Flat 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 Flat Washers Available in Property Class 8.8 Steel
| 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 |
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
