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.
How to Specify Flow-Drilling Screws for Your Application
- Size: Match the nominal size to the mating thread or hole. 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.
