Balls HK30 stem black

HK30 with a stud is a turning handle ball in nylon PA6, mounted on a threaded stud in zinc plated steel. The ball rotates freely around the stud, and that is the whole point: when you pull a crank or move a lever through an arc, the ball follows the movement of the hand instead of rubbing against the palm. The series comes in two versions, both with a ball diameter of 39 mm, with an M8 thread and 12 mm thread length or M10 and 16 mm thread length.

The classic place for a rotating ball is the crank handle: feed tables on milling machines, hand driven presses, vises, clamping devices and actuators where the same crank is pulled turn after turn. With a fixed ball the hand is forced to let go and move the grip at every turn; with a turning one the hand stays put while the ball spins. The difference is felt after a few minutes of cranking, and over a whole shift it spares both palm and wrist. Ergonomics is usually what decides when an operator has to stand at the same machine for hours; a spinning ball is a small detail with a big effect on the working day.

The combination of materials is chosen with care. The ball in PA6 is tough, impact resistant and pleasant to hold; the matte surface gives a grip even with oily gloves. The stud in zinc plated steel takes the mechanical loads, and the zinc layer gives basic corrosion protection in a normal workshop. Keep in mind though that zinc plated is not stainless; in wash bays or outdoors you should assess the conditions before you choose.

A plastic ball is gentle in itself as well. It does not turn cold to hold in winter in unheated premises, it does not conduct current and it does not damage what it happens to hit during quick movements. At the same time PA6 stands up to oil mist, splashes of cutting fluid and cleaning agents without the surface being noticeably affected; in other words the ball looks like new long after the machine around it has started to look worn.

Assembly is uncomplicated. The stud is screwed into the threaded hole in the crank arm and tightened against the seat; the ball keeps its free rotation after tightening. The ball is 53 mm high including the neck, and complete dimensions with neck diameter and shoulder are in the manufacturer's data sheet, so you can check the space around the crank before you order.

The choice between the versions is governed by the threaded hole in the crank and the load. M8 is enough for most hand cranks on smaller machines; M10 is the one to pick for heavier cranks, longer lever arms or simply when the hole is already M10. The 39 mm ball diameter gives a full grip surface that works for most hands, gloves included.

A common case is refurbishment. Older milling machines, lathes and presses often have cracked or sharp balls on the cranks, and a new ball with the same thread is a quick way to make the machine pleasant to crank again. Maintenance departments therefore tend to keep a few on the shelf; it is a simple comfort measure that also reduces the risk of blisters and pinched fingers.

The M8 version is supplied in packs of 200 pieces and the M10 in packs of 100. So there is volume for machine builders who draw the ball in as a standard component, and for the workshop that only needs to refurbish one machine a box lasts a long time.

Do you need a data sheet or help deciding whether M8 or M10 suits your crank? Call us directly.