---
title: "What Are Double-End Studs (DIN 938 / 939 / 940) Used For?"
description: "Double-End Studs (DIN 938 / 939 / 940) (DIN 938) are used for clamping a joint from both ends where a headed bolt cannot be used, tightened by the nuts rathe…"
url: https://engineeringhardware.com/applications/double-end-studs-din-938/
source: Engineering Hardware & Fasteners
---

# What Are Double-End Studs (DIN 938 / 939 / 940) Used For?

Bolts · DIN 938 · Application guide

Typical applications, the industries that specify double-end studs (din 938 / 939 / 940), and how to choose the right size, material and finish for the joint.

Double-End Studs (DIN 938 / 939 / 940) are used for clamping a joint from both ends where a headed bolt cannot be used, tightened by the nuts rather than by the fastener itself. They are manufactured to DIN 938, and the choice of size, property class and finish is driven by the load in the joint and the environment it sits in.

- **Primary duty:** Clamping a joint from both ends where a headed bolt cannot be used, tightened by the nuts rather than by the fastener itself
- **Governing standard:** DIN 938
- **Thread size range:** M8 to M24
- **Category:** Bolts

Application notes are general engineering guidance. Verify the property class and any approval requirement against your own design calculation.

![What Are Double-End Studs (DIN 938 / 939 / 940) Used For? application image](https://engineeringhardware.com/wp-content/uploads/2026/06/Stud-Bolt-Double-End-—-GB-T-15389-DIN-938-Series-092-—-GB-T-15389-DIN-938.webp)

Double-End Studs (DIN 938 / 939 / 940) are used primarily for clamping a joint from both ends where a headed bolt cannot be used, tightened by the nuts rather than by the fastener itself. This page lists the industries and assemblies where they are specified, the selection criteria that matter for each application, installation practice, and the cases where a different fastener type is the correct choice. Parts are supplied to DIN 938. Stocked across roughly M8 to M24, they cover general to heavy-duty work.

## Typical Applications for Double-End Studs (DIN 938 / 939 / 940)

The most common settings where these are specified:

- **Automotive & transport:** chassis, suspension and powertrain mounting points subject to vibration.
- **Heavy machinery:** securing gearboxes, frames and guarding on plant that sees shock loads.
- **Energy & infrastructure:** tower, pylon and pipework supports exposed to weather and long service life.
- **General machine building:** fastening covers, brackets, motors and sub-assemblies on production equipment.
- **Maintenance & repair (MRO):** a stocked size for servicing existing plant where the original fastener spec must be matched.

Product catalog

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## How to Specify Double-End Studs (DIN 938 / 939 / 940) for Your Application

- **Size:** Match the nominal size to the mating thread or hole. This product spans M8–M24; check the full table below for the exact dimensions of each size.
- **Strength class:** Choose the property class (e.g. 8.8, 10.9, 12.9 or A2/A4 stainless) for the load and environment, and tighten to the matching torque so the joint relies on preload, not friction.
- **Environment:** For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient.
- **Standard:** This product is supplied to DIN 938. Quoting the standard on your order guarantees interchangeable dimensions between suppliers.

## Installation & Assembly Practice

- Tighten to the torque for the size and property class with a calibrated wrench — the joint is held by preload, not by the thread friction alone.
- Ensure at least one full thread projects beyond the nut after tightening, and never re-use a bolt that has been tightened into yield.
- Under slotted or oversized holes, fit a hardened washer so the preload does not relax into the hole edge.

## Common Selection Mistakes with Double-End Studs (DIN 938 / 939 / 940)

- Specifying class 12.9 "to be safe" in a corrosive environment — high classes are more sensitive to hydrogen embrittlement and stress corrosion; 8.8 hot-dip galvanized often outlasts them outdoors.
- Choosing a length that puts the shear plane through the threaded portion when a plain shank (partially threaded bolt) was available.
- Mixing stainless bolts with plated-steel nuts: the joint loses its corrosion logic and can gall or seize.

## Where Double-End Studs (DIN 938 / 939 / 940) Are Not the Right Choice

Not for permanent joints that will never be opened (a rivet or weld is cheaper), and not where the head must sit flush — use a countersunk screw instead.

Custom manufacturing · Made to drawing

## Need a double-end studs (din 938 / 939 / 940) outside the standard range?

Dimensions, material, finish and form are specified from the drawing — a bolt outside the standard range is a variation on existing tooling rather than a new design. Made by cold heading or hot forging.

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

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

## Technical Drawing

Dimensioned line drawing of M8 Double-End Studs (DIN 938 / 939 / 940) to DIN 938. Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

- **Metal end bm (mm):** 8
- **For parent material:** Steel
- **Nut end (mm):** 8
- **Common overall length (mm):** 30~80
- **Property class:** 8.8
- **Sibling standard:** DIN 939 = 10 mm, DIN 940 = 16 mm

## Dimensions & Specifications (DIN 938)

| Thread size | Metal end bm (mm) | For parent material | Nut end (mm) | Common overall length (mm) | Property class | Reference standard | Sibling standard |
| --- | --- | --- | --- | --- | --- | --- | --- |
| M8 | 8 | Steel | 8 | 30~80 | 8.8 | DIN 938 | DIN 939 = 10 mm, DIN 940 = 16 mm |
| M10 | 10 | Steel | 10 | 35~100 | 8.8 | DIN 938 | DIN 939 = 12.5 mm, DIN 940 = 20 mm |
| M12 | 12 | Steel | 12 | 40~120 | 8.8 | DIN 938 | DIN 939 = 15 mm, DIN 940 = 24 mm |
| M16 | 16 | Steel | 16 | 50~160 | 8.8 | DIN 938 | DIN 939 = 20 mm, DIN 940 = 32 mm |
| M20 | 20 | Steel | 20 | 60~200 | 8.8 | DIN 938 | DIN 939 = 25 mm, DIN 940 = 40 mm |
| M24 | 24 | Steel | 24 | 70~240 | 8.8 | DIN 938 | DIN 939 = 30 mm, DIN 940 = 48 mm |

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 are Double-End Studs (DIN 938 / 939 / 940) used for?

Clamping a joint from both ends where a headed bolt cannot be used, tightened by the nuts rather than by the fastener itself. They are supplied to DIN 938.

### Which industries use Double-End Studs (DIN 938 / 939 / 940)?

They are commonly specified in automotive & transport, heavy machinery and energy & infrastructure, among other sectors.

### How do I choose the right size of Double-End Studs (DIN 938 / 939 / 940)?

Match the nominal size to the mating thread or hole. This product is available from M8 to M24; the full dimension table on this page lists each size.

### How tight should Double-End Studs (DIN 938 / 939 / 940) be torqued?

Tighten to the torque for the size and property class so the joint is held by bolt preload. The size pages and torque reference table give recommended values; use a calibrated torque wrench for anything structural.

### Can I get a quote for Double-End Studs (DIN 938 / 939 / 940) in the size and material I need?

Yes. Use the technical drawing and quote form on this page to set the size and options, then send the exact configuration to our team for pricing and lead time.

## Related Pages

Product page: [Double-End Studs (DIN 938 / 939 / 940) — specifications & sizes](https://engineeringhardware.com/fastener/double-end-studs-din-938/)

### Double-End Studs (DIN 938 / 939 / 940) Specification Guides

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