Property Class 8.8 Steel Grade 5 UNF Fine-Thread Hex Nuts 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 specification page for grade 5 unf fine-thread hex nuts in Property Class 8.8 Steel. Covers the grade designation (ISO 898-1 property class 8.8), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to ASME B18.2.2 / ASTM A563 / ASME B1.1.
Why Choose Property Class 8.8 Steel for Grade 5 UNF Fine-Thread Hex Nuts
The workhorse medium-carbon alloy class for structural joints. For grade 5 unf fine-thread hex nuts, 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 grade 5 unf fine-thread hex nuts 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 Grade 5 UNF Fine-Thread Hex Nuts, 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 Grade 5 UNF Fine-Thread Hex Nuts Available in Property Class 8.8 Steel
| Thread series | Material | Mating bolt grades | Finish options | Governing standards |
|---|
| UNF fine | medium carbon steel | Grade 5 or Grade 8 hex bolts | zinc plating or black oxide | ASME B18.2.2 / ASTM A563 |
| UNF fine | medium carbon steel | Grade 5 hex bolts | zinc plating | ASME B1.1 thread form |
Dimensions are independent of the material: every size above is available in Property Class 8.8 Steel.
Custom manufacturing · Made to drawing
Need this nut in a grade that is not listed?
Grade 8 8 Steel is one of the grades the catalog describes. Thread, height, across-flats, property class, locking feature and flange form can all be varied, including thread sizes the standard series does not run to. Made by cold heading or tapping.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
Custom nut manufacturingSend a drawing
Applications & Industries
What Grade 5 UNF Fine-Thread Hex Nuts are specified for, industry by industry.
Industries that specify Grade 5 UNF Fine-Thread Hex Nuts
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Industrial machinery
Higher thread engagement per unit of length.
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Maintenance
Zinc or black oxide to match the existing assembly.
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Automotive assembly
Fine threads give a closer preload adjustment.
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Agricultural equipment
Mates with Grade 5 and Grade 8 American hex bolts.
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Building services
Threaded rod, channel and suspension assemblies.
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Machine building & OEM
The clamping counter-face on studs and bolts throughout an assembly.
Typical applications
- selecting the finish to match the mating hardware
- confirming UNF rather than UNC before ordering
- pairing with a Grade 5 or Grade 8 inch bolt
- using the finer pitch where preload must be set closely
- locking an adjustment so it cannot drift
- joints re-torqued at a service interval
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.
- Match the class
- A nut below the bolt property class strips before the bolt reaches its own limit — pair class 8 nuts with 8.8 bolts, class 10 with 10.9.
Where to use something else
- Do not mix UNC and UNF of the same nominal size on one machine; the two look alike and will cross-thread.
Full application guide: where Grade 5 UNF Fine-Thread Hex Nuts are used, how to specify them, and the cases they are wrong for
