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Bolts · ASTM F3125/F3125M Grade F1852 and F2280

Property Class 8.8 Steel Tension-Control Structural Bolt Assemblies (TC / Twist-Off)

Mechanical properties, corrosion behaviour and the full dimensional range for this grade.

Property Class 8.8 Steel Tension-Control Structural Bolt Assemblies (TC / Twist-Off) 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.

Property Class 8.8 Steel Tension-Control Structural Bolt Assemblies (TC / Twist-Off) reference image

Property Class 8.8 Steel Tension-Control Structural Bolt Assemblies (TC / Twist-Off) are supplied to ASTM F3125/F3125M Grade F1852 and F2280. The grade provides requires plating (zinc) for corrosion protection and is magnetic; the practical service range is commonly limited to approx. +300 °C; confirm against the coating and the load. Property data, grade comparison and the full size table follow.

Why Choose Property Class 8.8 Steel for Tension-Control Structural Bolt Assemblies (TC / Twist-Off)

The workhorse medium-carbon alloy class for structural joints. For tension-control structural bolt assemblies (tc / twist-off), this matters when requires plating (zinc) for corrosion protection is the primary requirement.

Mechanical & Physical Properties

Grade designationISO 898-1 property class 8.8
Magnetic responseMagnetic
Service temperaturecommonly limited to approx. +300 °C; confirm against the coating and the load
Corrosion characteristicRequires plating (zinc) for corrosion protection

Corrosion Behavior in Service

Carbon and alloy steel tension-control structural bolt assemblies (tc / twist-off) 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.

Galvanic & Galling Considerations

For tension-control structural bolt assemblies (tc / twist-off) in steel, the dominant compatibility issue is hydrogen embrittlement at high property classes (10.9 and above) when electroplated. Plating must be followed by an appropriate baking treatment, or a non-electroplated finish (mechanical zinc, zinc flake) should be substituted.

Sizes of Tension-Control Structural Bolt Assemblies (TC / Twist-Off) Available in Property Class 8.8 Steel

SizeThread seriesAssemblyMinimum installation tension F1852 (lbf)Minimum installation tension F2280 (lbf)FinishReference standard
1/2-13UNCbolt + twist-off nut + washer12,55015,650Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
5/8-11UNCbolt + twist-off nut + washer19,90024,900Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
3/4-10UNCbolt + twist-off nut + washer29,45036,800Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
7/8-9UNCbolt + twist-off nut + washer40,75050,950Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
1-8UNCbolt + twist-off nut + washer53,45066,800Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
1-1/8-7UNCbolt + twist-off nut + washer67,35084,100Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
M16Metric optionbolt + twist-off nut + washerPlain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
M20Metric optionbolt + twist-off nut + washerPlain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280

Technical Drawing

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Specification
Business Information

Dimensions & Specifications (ASTM F3125/F3125M Grade F1852 and F2280)

SizeThread seriesAssemblyMinimum installation tension F1852 (lbf)Minimum installation tension F2280 (lbf)FinishReference standard
1/2-13UNCbolt + twist-off nut + washer12,55015,650Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
5/8-11UNCbolt + twist-off nut + washer19,90024,900Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
3/4-10UNCbolt + twist-off nut + washer29,45036,800Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
7/8-9UNCbolt + twist-off nut + washer40,75050,950Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
1-8UNCbolt + twist-off nut + washer53,45066,800Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
1-1/8-7UNCbolt + twist-off nut + washer67,35084,100Plain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
M16Metric optionbolt + twist-off nut + washerPlain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280
M20Metric optionbolt + twist-off nut + washerPlain, heat-treated alloy steelASTM F3125/F3125M Grade F1852 and F2280

Applications & Industries

Tension-Control Structural Bolt Assemblies are bought for a small number of well-defined jobs. These are the ones we ship them for. Stocked from 1/2-13 to M20 (screw size).

Industries that specify Tension-Control Structural Bolt Assemblies

  • Industrial fabrication One-pass structural assembly where repeatable tension matters more than later disassembly.
  • Steel erection Matched structural bolt assemblies tensioned in beam, column and splice connections.
  • Bridge construction Slip-critical steel joints where the final tension is set by the twist-off installation system.
  • Heavy transport Truck frames and chassis joints exposed to road vibration and cyclic load.
  • Food, pharma & cleanroom Stainless assemblies that are washed down, where the finish matters as much as the strength.
  • Machine building & OEM The default fastener on production equipment: covers, brackets, motor mounts and sub-assemblies tightened to a specified torque.

Typical applications

  • using the plain shank and heavy hex geometry for steel-to-steel joints
  • installing a matched bolt, nut and washer assembly with a controlled twist-off spline
  • setting structural tension without a separate torque reaction wrench on the nut
  • selecting F1852 or F2280 together with the required installation tension
  • 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 reuse the twisted-off spline or substitute a generic torque value for the grade-specific installation method.
  • 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 Tension-Control Structural Bolt Assemblies are used, how to specify them, and the cases they are wrong for

Video: Property Class 8.8 Steel Tension-Control Structural Bolt Assemblies (TC / Twist-Off)

CJFP Tension Control Bolts, TC Bolts or Twist Off Bolts

Third-party video, selected automatically for this topic. It is not produced by Engineering Hardware and is not a specification source — use the tables on this page for dimensional data.

Inside the plant

Manufactured in our own plant

This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided.

  1. Wire rod feeding into a cold heading machine
    01

    Cold heading

    Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail.

    Head dimensions and under-head radius checked at set-up and per shift.

  2. Thread rolling machine producing bolt threads
    02

    Thread rolling

    Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch.

    Go / no-go ring gauges to ISO 965 tolerance class 6g.

  3. Baskets of bolts staged for heat treatment
    03

    Heat treatment

    Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it.

    Core hardness and tensile tested per lot to ISO 898-1.

  4. Zinc plated bolts in a treatment basket
    04

    Surface treatment

    Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list.

    Coating thickness and neutral salt spray hours to ISO 9227.

Frequently Asked Questions

What corrosion resistance do Property Class 8.8 Steel Tension-Control Structural Bolt Assemblies (TC / Twist-Off) offer?

Property Class 8.8 Steel Tension-Control Structural Bolt Assemblies (TC / Twist-Off) provide requires plating (zinc) for corrosion protection with a service range of commonly limited to approx. +300 °C; confirm against the coating and the load.

When should I move from ISO 898-1 property class 8.8 to class 10.9 / 12.9 for Tension-Control Structural Bolt Assemblies (TC / Twist-Off)?

Step up to class 10.9 / 12.9 when the joint preload approaches the proof load of the current class. The higher class adds preload at the same diameter, often saving size and weight.

Is Property Class 8.8 Steel prone to hydrogen embrittlement?

Class 10.9 and above can be susceptible to hydrogen embrittlement when electroplated. Specify post-plating baking, or use mechanical-zinc / zinc-flake finishes which avoid the cathodic plating step.

Which finish is best for outdoor Tension-Control Structural Bolt Assemblies (TC / Twist-Off)?

For outdoor service in steel, hot-dip galvanizing gives the longest life; zinc-flake (Geomet/Delta-Tone family) gives a thinner film with excellent salt-spray performance; standard zinc plating is the lowest-cost option for general indoor / shielded outdoor use.

How do I request a quotation?

Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day.