Knobs HC30 bushing black

Knobs HC30 bushing are cylindrical handle knobs in nylon PA6 with an internal thread, meant to be screwed straight onto a threaded stud or bolt. The knob measures 25 mm in diameter and 30 mm in height, with a matte black surface; the thread comes in M6, M8 and M10, and the depth of the hole is given as 17 mm in the manufacturer's data sheet. You pick the thread size as a variant on the product page. The series comes from a Swedish maker of machine elements and belongs to the standard range of grips in the engineering industry.

PA6 is one of the most common engineering plastics in the industry, and in a knob the toughness of the material comes into its own. A knob gets dropped on the floor, takes knocks from tools and is tightened by hands in gloves; the nylon takes that handling without cracking, unlike more brittle plastics. The surface is closed, stands up to oil and grease in a normal workshop and the matte black hides dirt while matching the other controls in the same series.

The cylindrical shape makes the knob an all rounder among grips. The fingers get hold around the whole circumference, and the shape works just as well for pulling as for turning. Typical places are end knobs on control levers and pull rods, handles on small doors and sliding guards, and grips on fixtures and positioners where the operator moves a part many times per shift.

The thread is formed in the bushing of the knob in the same nylon, so it is entirely in plastic. That is plenty for hand force; a knob is not a bolted joint to be preloaded, it is a grip that has to stay put on its stud. If the knob sits in a place with vibration, a drop of thread locker or a lock nut can be wise, just as with metal knobs.

Nylon takes up some moisture, which is worth knowing from other contexts; for dimensionally critical machine parts it can matter, but for a knob it has no practical significance. The grip is unaffected, the thread still fits and the surface looks the same all year round. Here the material gets to show its strengths instead: toughness, wear resistance and low weight.

Pick the thread to match the stud you already have. M6 suits light controls and smaller levers, M8 is the usual middle size and M10 sits on heavier control arms. Check the length of the thread on the stud at the same time; the 17 mm hole depth sets the limit for how far the stud can reach in. All three versions have the same outside dimensions, so the feel in the hand is identical whatever the thread, which makes it easy to standardize on one and the same knob across the whole machine shop even when the studs vary. If the stud has a less common thread than that, a new bolt usually solves the matter faster than a special knob.

The knobs are supplied in packs of 500 pieces. That says something about who the product is meant for: manufacturing companies that fit the same knob on every unit, and maintenance departments that want a standard grip on the shelf instead of ordering single pieces every time a need comes up.

The same knob body also comes in the HC30 plain hole version, where the thread is replaced by a plain hole in 6, 8 or 10 mm for mounting on an unthreaded shaft. And if you need a knob that screws into a threaded hole instead of onto a stud, look at the mushroom shaped HC11 with a threaded steel stud.

Do you need help choosing the thread size? Get in touch.