Knobs HC11 stem black

Mushroom shaped knobs solve a different problem than cylindrical ones. Knobs HC11 stud are low, wide knobs in nylon PA6 with a threaded stud in zinc plated steel; the knob screws into a threaded hole in the part and becomes a grip with minimal overall height. The domed shape is made for pushing, sliding and turning with the palm rather than pulling with the whole hand.

The series consists of five versions in two sizes. The smaller dome measures 22 mm in diameter and 16.5 mm in height and comes with a stud in M4, M5 or M6; the larger measures 32 mm in diameter and 24 mm in height with a stud in M6 or M8. The stud length is 15 mm on all of them. The surface is matte black, and you pick size and thread as a variant on the product page.

The stud in zinc plated steel is an important difference from all-plastic knobs. The thread takes being screwed in and out many times without wearing, handles tightening with tools and fits straight into threaded holes in sheet metal, aluminum profiles and machine frames. The zinc plating gives basic protection against corrosion in normal indoor conditions; in damp or chemically tough settings it is therefore the stud, not the plastic, that sets the limit on service life.

The difference from the bushing knobs in the series is the direction of the joint. A bushing knob has an internal thread and screws onto a stud that is already on the machine; HC11 carries the thread itself and only needs a threaded hole. In new designs the hole is often the cheaper option, since it is drilled and tapped in the same setup as the rest of the machining on the part. When retrofitting existing equipment, what is already in place decides instead.

The mushroom shape turns up everywhere a control is operated with an open hand: sliding bolts on guard doors, locking knobs on fixtures, positioning devices on fences, shift levers on simpler machines and adjusting screws that the operator turns with two fingers. We also see them as end knobs on handles for test rigs and as grips on templates in joinery and composite workshops. The low profile also means the knob is rarely in the way; on a cramped control panel the difference between 16.5 and 30 mm of overall height can decide the layout.

The nylon does its usual job in the grip. PA6 is tough and impact resistant, does not crack from being dropped on the floor, and the matte surface gives a hold even for damp or oily fingers. The material also conducts heat poorly, so the knob feels pleasant even when the machine frame behind it is cold or hot. The smooth top of the dome is kind to the palm under repeated pressing.

Assembly: screw the knob in by hand and tighten lightly. If the joint has to be locked, use thread locking fluid on the steel stud, as on any machine screw. Check that the thread depth of the hole matches the 15 mm stud; in a through hole this is no problem, but in a blind hole the depth has to be enough for the dome to sit against the surface before the stud bottoms out.

The knobs are supplied in packs of 500 pieces, which points to series production and well stocked maintenance stores. If you are designing a machine family it can be worth staying with one dome size and varying the thread as needed; the two sizes share the same shape language, so mixed panels still look uniform.

Do you have questions about the thread on the stud or the dome size? Get in touch with us.