--- title: "What Are Flow-Drilling Screws Used For?" description: "Flow-Drilling Screws (Trade series (flow-drilling screws)) are used for forming a threaded hole through a sheet stack from one side by a flow-drilling screw." url: https://engineeringhardware.com/applications/flow-drilling-screws/ source: Engineering Hardware & Fasteners --- # What Are Flow-Drilling Screws Used For? Screws · Trade series (flow-drilling screws) · Application guide Typical applications, the industries that specify flow-drilling screws, and how to choose the right size, material and finish for the joint. Flow-Drilling Screws are used for forming a threaded hole through a sheet stack from one side by a flow-drilling screw. They are manufactured to Trade series (flow-drilling 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:** Forming a threaded hole through a sheet stack from one side by a flow-drilling screw - **Governing standard:** Trade series (flow-drilling screws) - **Thread size range:** M3 to M6 - **Category:** Screws Application notes are general engineering guidance. Verify the property class and any approval requirement against your own design calculation. ![What Are Flow-Drilling Screws Used For? application image](https://engineeringhardware.com/wp-content/uploads/2026/09/Flow-Drilling-Screws.webp) Flow-Drilling Screws are used primarily for forming a threaded hole through a sheet stack from one side by a flow-drilling screw. 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 Trade series (flow-drilling screws). Stocked across roughly M3 to M6, they cover light-duty and instrument-scale work. ## Typical Applications for Flow-Drilling Screws The most common settings where these are specified: - **Automotive body structures:** Flow-drilling screws create a threaded boss through one-side sheet access. - **Aluminum fabrication:** The process joins aluminum sheet without a separate pre-drilled thread. - **Magnesium housings:** One-side fastening avoids a loose nut inside a closed section. - **Industrial panels:** The clearance and sheet ranges define the process window. 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This product spans M3–M6; 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 (flow-drilling 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 Flow-Drilling 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 Flow-Drilling 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 flow-drilling screws outside the standard range? Material and finish are usually what drives a special — a grade the standard part is not stocked in, or a coating chosen against a salt-spray figure instead of a default. Made by cold heading or warm forging. Minimum order from 2,000 pieces; samples within 7 days of drawing approval. [Custom screw manufacturing](https://engineeringhardware.com/custom/screws/)[Send a drawing](https://engineeringhardware.com/custom/screws/#rfq) ## Technical Drawing Dimensioned line drawing of M3 Flow-Drilling Screws to Trade series (flow-drilling screws). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected. - **Clearance-hole diameter (mm):** 3.6~4.0 - **Steel sheet range (mm):** 0.3~1.8 - **Aluminum sheet range (mm):** 0.8~5.0 - **Magnesium sheet range (mm):** 0.8~3.5 - **Example drive / head:** varies by series ## Dimensions & Specifications (Trade series (flow-drilling screws)) | Thread size | Clearance-hole diameter (mm) | Steel sheet range (mm) | Aluminum sheet range (mm) | Magnesium sheet range (mm) | Example drive / head | | --- | --- | --- | --- | --- | --- | | M3 | 3.6~4.0 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | varies by series | | M3.5 | 4.3~4.8 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | varies by series | | M4 | 5.1~5.7 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | M4×20 stainless; PH2/PZ2/T25 examples | | M5 | 6.7~7.4 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | M5×20 stainless; PH2/PZ2/T25 examples | | M6 | 8.2~9.1 | 0.3~1.8 | 0.8~5.0 | 0.8~3.5 | varies by series | 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 ### Are Flow-Drilling Screws made to a recognized standard? Yes — they are manufactured to Trade series (flow-drilling screws), so dimensions are interchangeable between suppliers when you quote the standard on your order. ### What are Flow-Drilling Screws used for? Forming a threaded hole through a sheet stack from one side by a flow-drilling screw. They are supplied to Trade series (flow-drilling screws). ### Which industries use Flow-Drilling Screws? They are commonly specified in industrial panels, automotive body structures and aluminum fabrication, among other sectors. ### How do I choose the right size of Flow-Drilling Screws? Match the nominal size to the mating thread or hole. This product is available from M3 to M6; the full dimension table on this page lists each size. ### Can I get a quote for Flow-Drilling 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. ## Related Pages Product page: [Flow-Drilling Screws — specifications & sizes](https://engineeringhardware.com/fastener/flow-drilling-screws/) ### Flow-Drilling Screws Specification Guides ### Related Fastener Applications