Dome nut SM10

SM10 is a dome nut in polyethylene (PE) that threads onto protruding screw ends and studs to protect both the thread and anyone walking past. The series covers eight thread sizes from M3 to M16, all in natural with a matte surface; the height grows with the thread, from 5.3 mm for the smallest up to 23 mm for M16.

The function is simple but solves several problems at once. An open thread end collects dirt and paint residue, rusts in damp conditions and tears at both clothing and skin when someone walks into it. With a dome nut on the end the thread is enclosed, the edge is soft and the finish is neat; the screw joint looks finished instead of looking like something left over. The same goes inside the workshop: a row of capped thread ends on a machine guard signals order, and the next time the joint has to be undone the thread is clean and can be unscrewed without cleaning it out first.

Polyethylene is a soft and tough material with very low water absorption. The nut does not draw in moisture, does not crack from knocks and is not affected by most acids, bases and cleaning agents; chemical resistance is among the strongest properties of polyethylene. The material also insulates electrically, which can be an extra plus around electrical cabinets and instrument boxes.

The color deserves a word too. Natural means unpigmented polyethylene, a semi matte, bone white tone that neither draws the eye nor clashes with the other colors on the machine. On light colored interiors the dome blends in completely, and on dark frames it reads as a deliberate detail rather than a plastic cover added afterwards.

Designers put dome nuts on through bolted joints in machine guards, railings, interiors, carts and frames; maintenance uses them to tidy up and protect thread ends that would otherwise stand open. In public settings, shops, schools and sports halls, the soft plastic dome is one of the simplest ways to remove an injury risk without rebuilding anything.

The heights follow the thread size upwards: 5.3 mm for M3, 6.5 for M4, 7.5 for M5, 9.5 for M6, 12.1 for M8, 16 for M10, 18 for M12 and 23 mm for M16. That is worth noting in tight spaces, since the dome adds height on top of the joint. Check as well that the screw end does not stick out further than the dome can take; internal dimensions are in the manufacturer's data sheet.

SM10 is a protective element, not a load bearing nut. It does not replace the steel nut in the joint but is threaded on outside it, after the joint is tightened. Assembly needs no tools; the nut is threaded on by hand, and at service you unscrew it again just as easily.

You pick the size straight from the thread on the screw: an M8 screw gets an M8 dome. All eight sizes are supplied in packs of 500 pieces, so it is easy to keep the most common sizes in the store and pick them as needed. The natural color is neutral and blends in against both painted and untreated surfaces. If you need several sizes you mix freely between the variants on the product page.

Keep in mind that unpigmented polyethylene is not made for years of direct sunlight; for permanent outdoor mounting in an exposed position you should check the UV resistance against the data sheet first.

Would you like to double check that the thread and height match your joint? Get in touch and we will sort it out.