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Screws · DIN 6900-5 Z9 and DIN 6908 · Application guide

What Are SEMS Screws with Captive Conical Spring Washers Used For?

Typical applications, the industries that specify sems screws with captive conical spring washers, and how to choose the right size, material and finish for the joint.

SEMS Screws with Captive Conical Spring Washers are used for machine-screw assembly with a captive conical spring washer. They are manufactured to DIN 6900-5 Z9 and DIN 6908, 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
Machine-screw assembly with a captive conical spring washer
Governing standard
DIN 6900-5 Z9 and DIN 6908
Thread size range
M2.5 to M12
Category
Screws

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

What Are SEMS Screws with Captive Conical Spring Washers Used For? application image

SEMS Screws with Captive Conical Spring Washers (DIN 6900-5 Z9 and DIN 6908) are specified where the joint requires machine-screw assembly with a captive conical spring washer. The sections below cover the typical end-uses by industry, the size and material decisions for each, assembly practice, and the applications this fastener type is not suited to. Stocked across roughly M2.5 to M12, they cover general to heavy-duty work.

Typical Applications for SEMS Screws with Captive Conical Spring Washers

The most common settings where these are specified:

  • Control panels: captive spring-washer screws on covers and electrical equipment.
  • Light machinery: joints that settle slightly and need maintained contact.
  • Appliances: high-volume assembly with a washer that cannot fall away.
  • Instrument housings: small fasteners for repeated cover removal.

How to Specify SEMS Screws with Captive Conical Spring Washers for Your Application

  • Size: Match the nominal size to the mating thread or hole. This product spans M2.5–M12; check the full table below for the exact dimensions of each size.
  • Drive & head: Pick the drive (socket, cross, slot) and head style for the tool access and seating surface; a recessed drive resists cam-out under power tools.
  • 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 6900-5 Z9 and DIN 6908. Quoting the standard on your order guarantees interchangeable dimensions between suppliers.

Installation & Assembly Practice

  • Match the driver exactly to the recess (PH ≠ PZ; hex key sizes per ISO 2936) and keep the tool axial — side load is the main cause of stripped drives.
  • In tapped holes, engage a thread length of at least 1× the nominal diameter in steel, 2× in aluminum.
  • Set power tools to a torque that seats the head without embedding it into the mating surface.

Common Selection Mistakes with SEMS Screws with Captive Conical Spring Washers

  • Under-sizing the drive for the installation torque — a small recess at high torque strips before the screw is seated.
  • Using a countersunk head in thin sheet where the countersink removes most of the load-bearing material.
  • Specifying stainless in high-strength duty: A2-70 is roughly class 7 steel, not a 10.9 substitute.

Where SEMS Screws with Captive Conical Spring Washers Are Not the Right Choice

Not for high-preload structural joints (use a property-class bolt and nut), and not in thin sheet where a self-drilling or self-tapping type suits better.

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

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Specification
Business Information

Dimensions & Specifications (DIN 6900-5 Z9 and DIN 6908)

Thread sizePitch (mm)Washer inside diameter (mm)Washer outside diameter (mm)Washer thickness (mm)Material optionsReference standard
M2.50.452.25~2.355.7~6.00.5steel or A2 stainlessDIN 6900-5 Z9 and DIN 6908
M30.52.75~2.856.64~7.00.6steel or A2 stainlessDIN 6900-5 Z9 and DIN 6908
M40.73.6~3.728.64~9.01.0steel or A2 stainlessDIN 6900-5 Z9 and DIN 6908
M50.84.55~4.6710.57~11.01.2steel or A2 stainlessDIN 6900-5 Z9 and DIN 6908
M61.05.5~5.6213.57~14.01.5steel or A2 stainlessDIN 6900-5 Z9 and DIN 6908
M81.257.4~7.5517.57~18.02.0steel or A2 stainlessDIN 6900-5 Z9 and DIN 6908
M101.59.3~9.4522.48~23.02.5steel or A2 stainlessDIN 6900-5 Z9 and DIN 6908
M121.7511.0~11.1828.48~29.03.0steel or A2 stainlessDIN 6900-5 Z9 and DIN 6908
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

What material should SEMS Screws with Captive Conical Spring Washers be for outdoor use?

For damp, coastal or chemical environments specify A4 (316) stainless or a suitably coated steel. For indoor or dry use, A2 (304) stainless or zinc-plated steel is normally adequate.

Are SEMS Screws with Captive Conical Spring Washers made to a recognized standard?

Yes — they are manufactured to DIN 6900-5 Z9 and DIN 6908, so dimensions are interchangeable between suppliers when you quote the standard on your order.

What are SEMS Screws with Captive Conical Spring Washers used for?

Machine-screw assembly with a captive conical spring washer. They are supplied to DIN 6900-5 Z9 and DIN 6908.

Which industries use SEMS Screws with Captive Conical Spring Washers?

They are commonly specified in appliances, instrument housings and control panels, among other sectors.

Can I get a quote for SEMS Screws with Captive Conical Spring Washers 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.