Property Class 8.8 Steel Flow-Drilling Screws 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.
Material page for flow-drilling screws in Property Class 8.8 Steel (ISO 898-1 property class 8.8). The sizes below are the ones we supply; there is no published dimensional standard for this article, so the table rather than a standard number is what to quote. Corrosion behaviour is requires plating (zinc) for corrosion protection and the service range is commonly limited to approx. +300 °C; confirm against the coating and the load.
Why Choose Property Class 8.8 Steel for Flow-Drilling Screws
The workhorse medium-carbon alloy class for structural joints. For flow-drilling screws, 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 flow-drilling screws 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 Flow-Drilling Screws, 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 Flow-Drilling Screws Available in Property Class 8.8 Steel
| Thread size | Clearance-hole diameter (mm) | Steel sheet range (mm) | Aluminum sheet range (mm) | Magnesium sheet range (mm) | Example drive / head |
|---|
| M3 | 3.6~4.0 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | varies by series |
| M3.5 | 4.3~4.8 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | varies by series |
| M4 | 5.1~5.7 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | M4×20 stainless; PH2/PZ2/T25 examples |
| M5 | 6.7~7.4 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | M5×20 stainless; PH2/PZ2/T25 examples |
| M6 | 8.2~9.1 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | varies by series |
Dimensions are independent of the material: every size above is available in Property Class 8.8 Steel.
Custom manufacturing · Made to drawing
Need this screw in a grade that is not listed?
Grade 8 8 Steel is one of the grades the catalog describes. Material and finish are usually what drives a special — a grade the standard part is not stocked in, or a coating chosen against a salt-spray figure instead of a default. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
Custom screw manufacturingSend a drawing
Applications & Industries
What Flow-Drilling Screws are specified for, industry by industry. Stocked from M3 to M6.
Industries that specify Flow-Drilling Screws
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Magnesium housings
One-side fastening avoids a loose nut inside a closed section.
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Industrial panels
The clearance and sheet ranges define the process window.
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Automotive body structures
Flow-drilling screws create a threaded boss through one-side sheet access.
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Aluminum fabrication
The process joins aluminum sheet without a separate pre-drilled thread.
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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.
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Automotive & transport
Chassis, driveline and body fixings that see vibration and are assembled to a controlled preload.
Typical applications
- selecting the process for the sheet thickness
- using the specified drive and head for the assembly tool
- flow-drilling a thread into steel, aluminum or magnesium
- matching the clearance-hole range to the screw size
- assemblies that are dismantled for service and re-torqued
- joints where the property class is stated on the drawing
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 a flow-drilling screw outside its material or sheet-thickness window; heat and thread formation are process-dependent.
- 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 Flow-Drilling Screws are used, how to specify them, and the cases they are wrong for
