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Nuts · MS21055 and NASM25027

Property Class 8.8 Steel Aerospace Corner Self-Locking Nutplates

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

Property Class 8.8 Steel Aerospace Corner Self-Locking Nutplates 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 Aerospace Corner Self-Locking Nutplates reference image

Aerospace Corner Self-Locking Nutplates manufactured in Property Class 8.8 Steel (ISO 898-1 property class 8.8) are dimensioned to MS21055 and NASM25027. 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 Aerospace Corner Self-Locking Nutplates

The workhorse medium-carbon alloy class for structural joints. For aerospace corner self-locking nutplates, 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 aerospace corner self-locking nutplates 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 Aerospace Corner Self-Locking Nutplates, 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 Aerospace Corner Self-Locking Nutplates Available in Property Class 8.8 Steel

Thread sizeOverall length A (in)Mounting-hole spacing J (in)Width C (in)Nut height (in)Material optionsReference standard
6-320.6370.4860.3440.171cadmium-plated alloy steel or stainless steelMS21055 and NASM25027
8-320.637~0.8520.486~0.7070.344~0.5000.171~0.281cadmium-plated alloy steel or stainless steelMS21055 and NASM25027
10-320.637~0.8520.486~0.7070.344~0.5000.171~0.281cadmium-plated alloy steel or stainless steelMS21055 and NASM25027
1/4-280.637~0.8520.486~0.7070.344~0.5000.171~0.281cadmium-plated alloy steel or stainless steelMS21055 and NASM25027

Technical Drawing

Customize the parameters below — every spec field is editable, and the drawing redraws to match the values you choose. Changing the size will snap the other fields to that size's standard values; you can then override any individual value.

Sends the selected values to the quote form below.

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Specification
Business Information

Dimensions & Specifications (MS21055 and NASM25027)

Thread sizeOverall length A (in)Mounting-hole spacing J (in)Width C (in)Nut height (in)Material optionsReference standard
6-320.6370.4860.3440.171cadmium-plated alloy steel or stainless steelMS21055 and NASM25027
8-320.637~0.8520.486~0.7070.344~0.5000.171~0.281cadmium-plated alloy steel or stainless steelMS21055 and NASM25027
10-320.637~0.8520.486~0.7070.344~0.5000.171~0.281cadmium-plated alloy steel or stainless steelMS21055 and NASM25027
1/4-280.637~0.8520.486~0.7070.344~0.5000.171~0.281cadmium-plated alloy steel or stainless steelMS21055 and NASM25027

Applications & Industries

What Aerospace Corner Self-Locking Nutplates are specified for, industry by industry. Stocked from 6-32 to 1/4-28 (screw size).

Industries that specify Aerospace Corner Self-Locking Nutplates

  • Avionics brackets Serviceable hardware attached near a panel corner.
  • Transport interiors Compact self-locking threads behind trim and access panels.
  • Aircraft skin panels Corner-mounted self-locking nutplates in confined panel edges.
  • Aerospace equipment bays Fixed threaded points where a two-lug floating basket will not fit.
  • Building services Threaded rod, channel and suspension assemblies.
  • Machine building & OEM The clamping counter-face on studs and bolts throughout an assembly.

Typical applications

  • holding a service screw captive at the back of a thin panel
  • matching corner length, hole spacing, width and nut height to MS21055
  • providing a fixed corner thread with self-locking torque
  • placing a nutplate where edge access limits the mounting pattern
  • joints re-torqued at a service interval
  • completing a bolted joint on a stud, rod or bolt

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.
Vibration
Specified where cyclic load would loosen a plain nut or screw — rotating plant, rail, mobile equipment and anything that is not re-torqued in service.
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 substitute a floating two-lug nutplate when the corner pattern must stay fixed to the specified spacing.

Full application guide: where Aerospace Corner Self-Locking Nutplates are used, how to specify them, and the cases they are wrong for

Video: Property Class 8.8 Steel Aerospace Corner Self-Locking Nutplates

MS21076L4N Self-Locking Nutplates

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

When should I move from ISO 898-1 property class 8.8 to class 10.9 / 12.9 for Aerospace Corner Self-Locking Nutplates?

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 Aerospace Corner Self-Locking Nutplates?

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.

What's the service temperature limit for Property Class 8.8 Steel?

The practical service range is commonly limited to approx. +300 °C; confirm against the coating and the load.

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.