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Pins · Trade series (GN 615)

A4 (316) Stainless Steel Threaded Spring Plungers

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

A4 Stainless Steel Threaded Spring Plungers 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 Threaded Spring Plungers reference image

Material specification page for threaded spring plungers in A4 Stainless Steel. Covers the grade designation (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to Trade series (GN 615).

Why Choose A4 Stainless Steel for Threaded Spring Plungers

Specified for marine, coastal and chemical applications. For threaded spring plungers, 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

Corrosion Behavior in Service

A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Threaded Spring Plungers in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.

Comparable Grades

For Threaded Spring Plungers, 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 Threaded Spring Plungers Available in A4 Stainless Steel

Thread sizePlunger typesHousing materialBall materialSpring material
M2K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M3K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M4K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M5K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M6K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M8K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M12K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M20K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631

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 (Trade series (GN 615))

Thread sizePlunger typesHousing materialBall materialSpring material
M2K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M3K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M4K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M5K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M6K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M8K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M12K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631
M20K / KS / KN / KSNblackened steel or AISI 303 stainlesshardened steel or AISI 420C stainlessAISI 631

Applications & Industries

What Threaded Spring Plungers are specified for, industry by industry. Stocked from M2 to M20.

Industries that specify Threaded Spring Plungers

  • Conveyor changeover Low-force positioning of guides and adjustable stops.
  • Instrument controls Small locating contacts under knobs, slides and adjustment parts.
  • Jig and fixture building Threaded spring plungers used for stops, detents and repeat location.
  • Machine guarding Spring contacts that hold removable covers in a chosen position.
  • Agricultural & plant Implement connections made and broken in the field.
  • Gearboxes & housings Dowelled joints where the bolts clamp and the pins locate.

Typical applications

  • setting a repeatable detent without a loose removable pin
  • matching ball and housing material to the contact environment
  • providing a threaded spring-loaded ball contact
  • choosing standard, high-load or locking-slot plunger types
  • pivot and hinge joints loaded in shear
  • quick connections made and broken by hand

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.
Hole preparation
The hole is half the specification: a ground dowel needs a reamed H7 hole, a grooved or spring pin will hold in a drilled one.

Where to use something else

  • Do not use a spring plunger as the primary shear retainer or as a substitute for a clamp bolt.

Full application guide: where Threaded Spring Plungers 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

Is A4 Stainless Steel food-grade?

A4 (316) is the standard food-contact stainless grade in most jurisdictions, particularly where chloride exposure (brines, dairy CIP) is present.

Can A4 Stainless Steel Threaded Spring Plungers be used with aluminum?

Yes, but stainless drives mild galvanic corrosion of aluminum in wet service — isolate with a coating, sleeve or paint, or accept the trade-off if the joint is dry and indoor.

What's the service temperature limit for A4 Stainless Steel?

The practical service range is approx. -200 °C to +400 °C, subject to the property class and the joint.

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.

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.