Nuts · Trade series (rubber blind nuts)

A4 (316) Stainless Steel EPDM Rubber Well Nuts

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

A4 Stainless Steel EPDM Rubber Well Nuts 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 Stainless Steel EPDM Rubber Well Nuts are supplied to Trade series (rubber blind nuts). The grade provides superior, including marine and chloride environments and is largely non-magnetic; the practical service range is approx. -200 °C to +400 °C, subject to the property class and the joint. Property data, grade comparison and the full size table follow.

Why Choose A4 Stainless Steel for EPDM Rubber Well Nuts

Specified for marine, coastal and chemical applications. For epdm rubber well nuts, this matters when superior, including marine and chloride environments is the primary requirement.

Mechanical & Physical Properties

Grade designation	ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80
Magnetic response	Largely non-magnetic
Service temperature	approx. -200 °C to +400 °C, subject to the property class and the joint
Corrosion characteristic	Superior, 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 EPDM Rubber Well Nuts in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.

Galvanic & Galling Considerations

Two important notes for stainless epdm rubber well nuts: (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.

Using Stainless Fasteners in Aluminum

Stainless steel is more noble than aluminum, so with an electrolyte present — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. Area ratio decides how bad it gets: a small stainless fastener in a large aluminum section is normally acceptable, a large stainless fastener in thin aluminum is not. Where the joint gets wet, isolate the metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.

Sizes of EPDM Rubber Well Nuts Available in A4 Stainless Steel

Thread size	Representative hole diameter (mm)	Representative grip range (mm)	Temperature range (u00b0C)	Representative tightening torque (Nu00b7m)	Body / insert
M3	8.0	0.4~4.0	-30~+80	0.5	EPDM rubber / stainless threaded insert
M4	8.0	0.4~4.0	-30~+80	0.4	EPDM rubber / stainless threaded insert
M5	9.7	0.4~4.9	-30~+80	0.6	EPDM rubber / stainless threaded insert
M6	12.8	0.4~4.0 or 0.8~4.7	-30~+80	1.0	EPDM rubber / stainless threaded insert
M8	16.0	0.4~4.0	-30~+80	1.5	EPDM rubber / stainless threaded insert

Technical Drawing

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Specification

Item / category Standard Size(s) Material / finish Quantity

Business Information

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Notes

Dimensions & Specifications (Trade series (rubber blind nuts))

Thread size	Representative hole diameter (mm)	Representative grip range (mm)	Temperature range (u00b0C)	Representative tightening torque (Nu00b7m)	Body / insert
M3	8.0	0.4~4.0	-30~+80	0.5	EPDM rubber / stainless threaded insert
M4	8.0	0.4~4.0	-30~+80	0.4	EPDM rubber / stainless threaded insert
M5	9.7	0.4~4.9	-30~+80	0.6	EPDM rubber / stainless threaded insert
M6	12.8	0.4~4.0 or 0.8~4.7	-30~+80	1.0	EPDM rubber / stainless threaded insert
M8	16.0	0.4~4.0	-30~+80	1.5	EPDM rubber / stainless threaded insert

Applications & Industries

Where EPDM Rubber Well Nuts are used, and what decides the specification in each case. Stocked from M3 to M8.

Industries that specify EPDM Rubber Well Nuts

Vehicle body panels Rubber well nuts isolate and seal trim fasteners through thin skins.
Motorcycle service Blind rubber inserts provide a thread where the rear face is inaccessible.
Outdoor enclosures EPDM accommodates panel movement and keeps a small hole sealed.
Equipment covers Stainless inserts resist corrosion while the rubber body clamps the panel.
Maintenance & MRO Replacements matched to the existing bolt class, thread and finish.
Building services Threaded rod, channel and suspension assemblies.

Typical applications

adding a blind threaded point to a thin panel
matching hole diameter and grip range to the EPDM body
tightening only to the representative torque for the size
using the rubber body for isolation and sealing
completing a bolted joint on a stud, rod or bolt
locking an adjustment so it cannot drift

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.
Sealed joints: Used where the fixing has to keep water or air out as well as hold — the elastomer, not the fastener, decides service life.
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 over-tighten a well nut; excess compression can pull the insert through the panel or damage the seal.

Full application guide: where EPDM Rubber Well Nuts 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.

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.
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.
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.
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 EPDM Rubber Well Nuts magnetic?

A4 Stainless Steel EPDM Rubber Well Nuts are largely non-magnetic.

What corrosion resistance do A4 Stainless Steel EPDM Rubber Well Nuts offer?

A4 Stainless Steel EPDM Rubber Well Nuts 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 EPDM Rubber Well Nuts?

For EPDM Rubber Well Nuts, 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.