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Screws · Trade series (drilled-spanner security screws) · Application guide

What Are Drilled-Spanner Security Screws Used For?

Typical applications, the industries that specify drilled-spanner security screws, and how to choose the right size, material and finish for the joint.

Drilled-Spanner Security Screws are used for fixings in public or unsupervised places that must resist casual removal with ordinary tools. They are manufactured to Trade series (drilled-spanner security screws), 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
Fixings in public or unsupervised places that must resist casual removal with ordinary tools
Governing standard
Trade series (drilled-spanner security screws)
Nominal diameter range
4-40 undercut to 8-32 standard
Category
Screws

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

What Are Drilled-Spanner Security Screws Used For? application image

Drilled-Spanner Security Screws (Trade series (drilled-spanner security screws)) are specified where the joint requires fixings in public or unsupervised places that must resist casual removal with ordinary tools. 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 4 mm to 8 mm, they cover general to heavy-duty work.

Typical Applications for Drilled-Spanner Security Screws

The most common settings where these are specified:

  • Public fixtures: Two-hole drives resist common screwdrivers and casual tampering.
  • Washroom equipment: Stainless flat-head forms keep visible panels flush.
  • Retail displays: Special drive hardware slows unauthorized removal.
  • Equipment enclosures: 4-40 through 8-32 examples fit small service panels.

How to Specify Drilled-Spanner Security Screws for Your Application

  • Size: Match the nominal size to the mating thread or hole. This product spans 4 mm–8 mm; 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 Trade series (drilled-spanner security screws). 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 Drilled-Spanner Security Screws

  • 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 Drilled-Spanner Security Screws 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.

Custom manufacturing · Made to drawing

Need a drilled-spanner security screws outside the standard range?

Where the standard stops, the drawing takes over: fine pitches, left-hand threads, partial threading, and property classes above the catalogued grade where material and heat treatment allow. Made by cold heading or warm forging.

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

Custom screw manufacturingSend a drawing

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.

Dimensioned line drawing of 4-40 undercut Drilled-Spanner Security Screws to Trade series (drilled-spanner security screws). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.
Head form
flat 82-degree
Head diameter (in)
0.225
Head height (in)
0.047
Length options (in)
1/4
Drive
two-hole drilled spanner
Material
18-8 stainless steel
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 (Trade series (drilled-spanner security screws))

Thread sizeHead formHead diameter (in)Head height (in)Length options (in)DriveMaterial
4-40 undercutflat 82-degree0.2250.0471/4two-hole drilled spanner18-8 stainless steel
6-32 standardflat 82-degree0.2620.0831/4~2two-hole drilled spanner18-8 stainless steel
8-32 standardflat 82-degree0.3120.1001/4~2two-hole drilled spanner18-8 stainless steel
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 Drilled-Spanner Security Screws 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 Drilled-Spanner Security Screws made to a recognized standard?

Yes — they are manufactured to Trade series (drilled-spanner security screws), so dimensions are interchangeable between suppliers when you quote the standard on your order.

What are Drilled-Spanner Security Screws used for?

Fixings in public or unsupervised places that must resist casual removal with ordinary tools. They are supplied to Trade series (drilled-spanner security screws).

Which industries use Drilled-Spanner Security Screws?

They are commonly specified in public fixtures, washroom equipment and retail displays, among other sectors.

Can I get a quote for Drilled-Spanner Security Screws 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.