STAINLESS STEEL HEXAGON WASHER HEAD SELF DRILLING DIN 7504K

Hexagon Washer Head Self Drilling DIN 7504K — DIN 7504K is a self-drilling, self-tapping screw with an integral hexagon washer head - the head and washer are forged as one piece rather than assembled, so there's no loose washer to line up or lose during installation. The wide flange spreads clamping load across thin steel or lightly profiled sheet, making it the standard choice for fixing purlins, girts, and light-gauge steel sections, along with roofing and cladding sheet to a steel structure, wherever a bonded weather seal isn't part of the specification. Where the fixing point will be exposed to rain or washdown, the sealing-washer version of this head style is the better pick, since the plain washer head gives load spread but no elastomeric seal. Point selection matters as much as grade here: the drilling point has to be matched to the combined thickness of the steel being joined, since an undersized point will burn out before it penetrates, while an oversized point wastes thread engagement on thin material. Stainless self-drilling screws are usually made with a hardened point in a martensitic grade such as 410 or 420, rather than a true A2 or A4 austenitic body throughout, because austenitic stainless doesn't harden enough to drill through steel - worth checking with the supplier if full A4-level corrosion resistance is needed for every part of the fastener, such as in a coastal or heavy-washdown building. For most steel-frame construction and general cladding work, A2-equivalent corrosion resistance on the exposed shank and head is sufficient; the extra cost of A4 is worth paying mainly where the building is coastal, uses de-icing salt nearby, or the fixing sits in a permanently damp or chemically aggressive environment. DIN 7504K governs the head form, washer flange, thread, and drive recess dimensions, keeping washer-head self-drillers interchangeable across manufacturers.

FAQs
How does the self-drilling tip work?
The drill point cuts through the base material like a twist drill. Once through, the thread form engages and taps its own mating thread as the screw is driven home, so drilling and thread-forming happen in one pass.

How is a DIN 7504K screw installed?
It's driven with a power tool fitted with the matching hex socket, at a speed and pressure that lets the point drill through before the thread starts to engage. Running speed too high can overheat and blunt the point.

What determines whether the sealing-washer version is needed instead?
If the fixing will be exposed to weather, condensation, or washdown, choose the sealing-washer variant - DIN 7504K's integral washer prevents pull-through and spreads load, but it doesn't compress to form a weatherproof seal.