Property Class 12.9 Steel Grade 5 UNF Fine-Thread Hex Nuts are supplied to ISO 898-1 property class 12.9. Corrosion behaviour is requires plating or black-oxide 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 highest common strength class, for high-load machine assembly.
- Grade
- ISO 898-1 property class 12.9
- Corrosion resistance
- Requires plating or black-oxide 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 12.9 Steel. Covers the grade designation (ISO 898-1 property class 12.9), 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 12.9 Steel for Grade 5 UNF Fine-Thread Hex Nuts
The highest common strength class, for high-load machine assembly. For grade 5 unf fine-thread hex nuts, this matters when requires plating or black-oxide protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 898-1 property class 12.9 |
|---|
| Magnetic response | Magnetic |
|---|
| Service temperature | commonly limited to approx. +300 °C; confirm against the coating and the load |
|---|
| Corrosion characteristic | Requires plating or black-oxide 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 8.8 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 12.9 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 12.9 Steel.
Custom manufacturing · Made to drawing
Need this nut in a grade that is not listed?
Grade 12 9 Steel is one of the grades the catalog describes. Thread size is the obvious variable and rarely the interesting one — height for clearance, across-flats for the tool already in the cell, and the locking feature for the vibration actually present. 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
-
Industrial machinery
Higher thread engagement per unit of length.
-
Maintenance
Zinc or black oxide to match the existing assembly.
-
Automotive assembly
Fine threads give a closer preload adjustment.
-
Agricultural equipment
Mates with Grade 5 and Grade 8 American hex bolts.
-
Building services
Threaded rod, channel and suspension assemblies.
-
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
