---
title: "M8 EPDM Rubber Well Nuts Dimensions"
description: "M8 EPDM Rubber Well Nuts: coarse thread pitch 1.25 mm. Tightening torque 24 Nm at class 8.8."
url: https://engineeringhardware.com/guide/size/m8-epdm-rubber-well-nuts/
source: Engineering Hardware & Fasteners
---

# M8 EPDM Rubber Well Nuts Dimensions

Nuts · Trade series (rubber blind nuts)

Controlling dimensions to Trade series (rubber blind nuts), with spanner or drive size and tightening torque.

M8 EPDM Rubber Well Nuts dimensions to Trade series (rubber blind nuts): coarse thread pitch 1.25 mm. Tighten to approximately 24 Nm at property class 8.8 in a dry, as-supplied condition.

- **Coarse thread pitch:** 1.25 mm
- **Tightening torque (class 8.8):** 24 Nm

Figures are nominal values from the governing standard. Confirm against the tolerance class for your application before machining or ordering.

![M8 EPDM Rubber Well Nuts Dimensions reference image](https://engineeringhardware.com/wp-content/uploads/2026/09/EPDM-Rubber-Well-Nuts-Rubber-Blind-Nuts.webp)

M8 EPDM Rubber Well Nuts are manufactured to Trade series (rubber blind nuts). This page lists the controlling dimensions for the M8 size together with the drive and the installation notes for this type.

Values are taken from the governing standard rather than from a general machine-thread table, because this type is not selected on one.

## M8 Dimensional Row (Trade series (rubber blind nuts))

| Thread size | Representative hole diameter (mm) | Representative grip range (mm) | Temperature range (u00b0C) | Representative tightening torque (Nu00b7m) | Body / insert |
| --- | --- | --- | --- | --- | --- |
| M8 | 16.0 | 0.4~4.0 | -30~+80 | 1.5 | EPDM rubber / stainless threaded insert |

## Spanner & Drive for M8 EPDM Rubber Well Nuts

Drive geometry for M8 EPDM Rubber Well Nuts is given by the row above; match the tool to the listed values.

## Tightening Torque for M8

| Class 8.8 (dry, ~µ 0.125) | ≈ 24 Nm |
| --- | --- |
| Class 10.9 (dry, ~µ 0.125) | ≈ 36 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 42 Nm |

Indicative dry-joint values. Lubrication can lower the required torque by 15–25%. Always confirm against the joint design, especially when going up a strength class.

## Proof Load & Strength for M8

Nuts are graded to ISO 898-2 by the proof load the nut itself will hold (classes 04, 05, 5, 6, 8, 10 and 12), not by the 8.8 / 10.9 / 12.9 scale used for bolts. A class-8 nut is the correct mate for a class-8.8 bolt, and the joint is designed on the bolt, so no bolt-tension figure is quoted here.

## Mating Parts for M8

Pair M8 with the matching M8 bolt or screw, plus a M8 flat washer where required to distribute load on softer materials.

## When to Step Up or Down from M8

When the joint preload approaches the proof load of M8 class 8.8, step up to M10 class 8.8 (or move to M8 class 10.9). When the joint is over-specified, M6 often saves weight and cost without losing the safety margin.

Custom manufacturing · Made to drawing

## Need EPDM rubber well nuts in a size this table does not list?

This page covers M8 EPDM rubber well nuts. Height and across-flats are the two most often changed — a thinner nut for clearance, a larger hex for a tool that is already on the line. Made by cold heading or tapping.

Minimum order from 2,000 pieces; samples within 7 days of drawing approval.

[Custom nut manufacturing](https://engineeringhardware.com/custom/nuts/)[Send a drawing](https://engineeringhardware.com/custom/nuts/#rfq)

## Technical Drawing

Dimensioned line drawing of M8 EPDM Rubber Well Nuts to Trade series (rubber blind nuts). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

- **Representative hole diameter (mm):** 16.0
- **Representative grip range (mm):** 0.4~4.0
- **Temperature range (u00b0C):** -30~+80
- **Representative tightening torque (Nu00b7m):** 1.5
- **Body / insert:** EPDM rubber / stainless threaded insert

## 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 |

Product catalog

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## Applications & Industries for M8 EPDM Rubber Well Nuts

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](https://engineeringhardware.com/applications/epdm-rubber-well-nuts/)

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](https://engineeringhardware.com/wp-content/uploads/2026/08/09-wire-rod-feed-cold-heading-machine.webp) 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](https://engineeringhardware.com/wp-content/uploads/2026/08/03-thread-rolling-machine-bolt-production.webp) 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](https://engineeringhardware.com/wp-content/uploads/2026/08/05-heat-treatment-baskets-black-bolts.webp) 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](https://engineeringhardware.com/wp-content/uploads/2026/08/23-zinc-plated-bolts-treatment-basket.webp) 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 is the coarse-thread pitch of M8 for EPDM Rubber Well Nuts?

For M8 the standard coarse pitch is 1.25 mm — this is the value used for EPDM Rubber Well Nuts.

### What clearance and tapping drill suit M8?

Use a 9 mm clearance hole (ISO 273 medium) for through-fixing, or a 6.75 mm tapping drill for a coarse M8 thread.

### What is the height of an M8 nut?

The nominal height of a style-1 ISO 4032 M8 nut is in the spec table on this page. Style-2 (thick) is approximately 1.1× this height; thin (ISO 4035 / DIN 439) is approximately 0.5×.

### 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.

## Related Pages

[View the full EPDM Rubber Well Nuts page](https://engineeringhardware.com/fastener/epdm-rubber-well-nuts/)

### More EPDM Rubber Well Nuts Guides