Skip to content
WhatsApp
Request a Quote
Nuts · MS21055 and NASM25027

A4 (316) Stainless Steel Aerospace Corner Self-Locking Nutplates

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

A4 Stainless Steel Aerospace Corner Self-Locking Nutplates are supplied to ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80. Corrosion behaviour is superior, including marine and chloride environments, the material is largely non-magnetic, and the usable service range is approx. -200 °C to +400 °C, subject to the property class and the joint. In practice this grade is specified for marine, coastal and chemical applications.

Grade
ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80
Corrosion resistance
Superior, including marine and chloride environments
Magnetic response
Largely non-magnetic
Service temperature
approx. -200 °C to +400 °C, subject to the property class and the joint

Property values are typical for the grade. Certified mechanical test data is available on request for production orders.

A4 (316) Stainless Steel Aerospace Corner Self-Locking Nutplates reference image

A4 Stainless Steel (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80) is specified for marine, coastal and chemical applications. When aerospace corner self-locking nutplates are specified in this grade, the dimensions remain per MS21055 and NASM25027; the material determines corrosion behavior (superior, including marine and chloride environments) and the service temperature range (approx. -200 °C to +400 °C, subject to the property class and the joint). Both are covered below with the size table.

Why Choose A4 Stainless Steel for Aerospace Corner Self-Locking Nutplates

Specified for marine, coastal and chemical applications. For aerospace corner self-locking nutplates, this matters when superior, including marine and chloride environments is the primary requirement.

Mechanical & Physical Properties

Grade designationISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80
Magnetic responseLargely non-magnetic
Service temperatureapprox. -200 °C to +400 °C, subject to the property class and the joint
Corrosion characteristicSuperior, including marine and chloride environments

Galvanic & Galling Considerations

Two important notes for stainless aerospace corner self-locking nutplates: (1) stainless can gall on stainless threads under load — use a thread lubricant or anti-galling compound, especially for M6 and below; (2) when joined to aluminum or galvanized steel, stainless can drive galvanic corrosion of the less-noble metal in wet service — isolate with a coating or sleeve where appropriate.

Comparable Grades

For Aerospace Corner Self-Locking Nutplates, the alternative stainless grade is A2 (304). A2 (304) suits general indoor and outdoor service; A4 (316) adds molybdenum for marine and chloride environments. Where higher strength matters more than corrosion, switch to plated alloy-steel class 8.8 or 10.9.

Using Stainless Fasteners in Aluminum

Stainless steel is more noble than aluminum, so in the presence of an electrolyte — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. The effect is driven by the area ratio: a small stainless fastener in a large aluminum section is normally acceptable, while a large stainless fastener in thin aluminum is not. Where the joint is wet, isolate the two metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.

Sizes of Aerospace Corner Self-Locking Nutplates Available in A4 Stainless 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.

Request a Quote

The form below follows the current technical drawing configuration. Change the drawing values above and the request details update automatically.

Request a Quotation

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

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

Can A4 Stainless Steel replace plated alloy steel structurally?

Only at the standard strength classes — A2-70 / A4-80 are roughly equivalent to class 7 steel; A4-100 reaches class 8.8. For class 10.9 or 12.9 strength, plated alloy steel is required.

Are A4 Stainless Steel Aerospace Corner Self-Locking Nutplates magnetic?

A4 Stainless Steel Aerospace Corner Self-Locking Nutplates are largely non-magnetic.

What corrosion resistance do A4 Stainless Steel Aerospace Corner Self-Locking Nutplates offer?

A4 Stainless Steel Aerospace Corner Self-Locking Nutplates provide superior, including marine and chloride environments with a service range of approx. -200 °C to +400 °C, subject to the property class and the joint.

Should I choose A4 Stainless Steel or A2 (304) for Aerospace Corner Self-Locking Nutplates?

For Aerospace Corner Self-Locking Nutplates, A4 Stainless Steel suits general indoor and outdoor use; A2 (304) is preferred for marine, coastal and chemical environments. Choose by corrosion exposure first.

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.