A2 Stainless Dome Nuts DIN 1587

A2 stainless steel dome nuts, manufactured to DIN 1587 in sizes M4 to M16, with M3 as an additional size in the same domed shape, are also widely known as acorn nuts or cap nuts. Their defining feature is a smooth, fully rounded cap that closes over the end of a bolt or threaded rod, completely enclosing the exposed thread rather than leaving it open the way a standard hex nut does.

Made from A2 austenitic stainless steel, they combine the everyday convenience of a standard hexagon nut, fitted and removed with a normal spanner or socket, with strong resistance to rust and general corrosion. That makes them a reliable choice for fittings exposed to the weather, as A2 stainless steel remains rust-resistant even with frequent exposure to the elements. Because the dome fully covers the thread, it also keeps out dust, moisture and knocks that would otherwise mark or damage an open thread end, while giving the fixing a neat, rounded, professional appearance wherever it is visible.

Because the domed top hides the sharp, exposed end of the bolt, these nuts suit any visible fixing where a bare thread end would otherwise catch on a hand, sleeve or passing object. The standard hexagon base means they are just as easy to fit as an ordinary hex nut: no dome-specific spanner, socket or fitting technique is needed, just the correct size matched from the table below.

Key Features

• Manufactured to the DIN 1587 standard in sizes M4 to M16, with M3 as an additional size in the same domed shape
• A2 austenitic stainless steel construction gives strong resistance to rust and general corrosion
• Smooth, fully rounded dome cap completely encloses the exposed end of the bolt or threaded rod, protecting the thread from damage
• Snag-free, rounded profile removes the sharp exposed thread end left by a standard nut, safer for hands, clothing and anyone brushing past
• Closed dome shields the thread from dust, moisture and knocks, on top of the general corrosion resistance of the A2 stainless steel itself
• Standard hexagon base takes a normal spanner or socket, so fitting and removal need no specialist tools
• Clean, rounded finish suited to visible fixings where appearance matters as much as function
• Nine sizes from M3 up to M16, with width across flats, nut height and dome diameter listed for every size, covering small fixings through to heavier threaded rod

Specification

The table below gives the width across flats (the spanner or socket size), overall nut height and dome diameter for every size in the range, and the DIN 1587 thread pitch for M4 to M16, with imperial equivalents shown alongside each metric measurement.

Typical Applications

The combination of a corrosion-resistant A2 stainless build and a smooth, snag-free dome makes these nuts useful wherever a fixing needs to look tidy and feel smooth, not just hold securely. Common uses include:

• Furniture making and restoration, where a neat, rounded finish is preferred to an exposed nut and washer
• Shopfitting and cabinetry, on visible fixings that need to look as good as they perform
• Automotive and motorcycle trim, including wheel trims (hubcaps) on cars and vans, plus bicycles and other vehicles where appearance matters, with a corrosion-resistant finish that suits fixing points exposed to the weather
• Balustrades, handrails and staircases, where the rounded dome covers the sharp thread end that would otherwise catch hands or clothing
• Playground and outdoor play equipment, for a snag-free, rounded finish on exposed fixings
• Garden structures and fencing, where A2 stainless copes well with damp conditions and outdoor weathering
• Covering exposed threaded studs on machinery guards and control panels, protecting both the thread and anyone working nearby

Because the range spans M3 up to M16, it covers everything from fine, precision fixings on small assemblies through to heavier threaded rod on structural or outdoor work, all finished with the same corrosion-resistant, snag-free dome.

Installation Guidance

Choose the dome nut that matches the diameter of your bolt or threaded rod (for example, an M8 dome nut for M8 threaded bar) using the thread size column in the table above. Before fitting, make sure the exposed end of your fixing will sit fully inside the dome; if the thread protrudes too far, either trim the rod back before fitting the dome nut or use a shorter bolt so the full thread sits inside the cap. Tighten with a standard spanner or socket sized to the width across flats given in the table, the same tool you would use on an equivalent standard hex nut, so no specialist equipment is needed. Matching the correct tool size to the width across flats, rather than using one that is slightly too large, also helps avoid rounding the corners of the nut when tightening.

Common Questions

What is a dome nut?
A dome nut, also called an acorn nut or cap nut, is a hexagon nut with a closed, rounded top. It screws onto the end of a bolt or threaded rod and covers the exposed thread end for a neat, snag-free finish.

What sizes are available?
Nine sizes: M3, M4, M5, M6, M8, M10, M12, M14 and M16. M4 to M16 are made to DIN 1587; M3 is an additional size in the same domed shape.

What size spanner do I need?
Measured across the flats: 5.5mm for M3, 7mm for M4, 8mm for M5, 10mm for M6, 13mm for M8, 17mm for M10, 19mm for M12, 22mm for M14 and 24mm for M16.

Which dome nut fits my bolt?
Match the thread size: an M8 bolt or threaded rod needs an M8 dome nut, an M10 bolt an M10 dome nut, and so on.

Are they rust-resistant?
Yes. They are made from A2 stainless steel, which remains rust-resistant even with frequent exposure to the elements.