Balls HK34 press fit black

HK34 is a handle ball in nylon PA6 with a matte surface, built to be pressed onto a plain stud with no thread. The series covers fourteen versions in four ball diameters, 20, 25, 33 and 40 mm, with hole diameters from 4 to 16 mm; you pick the size as a variant straight on the product page. The design is similar to DIN 319, the ball knob standard that most designers recognize from machine drawings, which makes the ball easy to specify as a replacement in existing designs.

A press fit means the ball is mounted by being pressed onto a stud with a slight oversize. No thread, no glue and no lock nut are needed; the ball is held by the radial tension in the plastic. That makes assembly fast in series production and gives a joint with no loose parts that can vibrate apart. PA6 has the toughness needed for the hole to expand during pressing without cracking, and the material springs back against the stud with an even grip all round.

The dimension logic is straightforward. D gives the ball diameter, d1 the hole diameter and t the hole depth. The smallest ball at 20 mm has a total height of 18 mm and a hole depth of 10 mm, while the largest at 40 mm is 35 mm high with a hole depth up to 26 mm. The holes come in several steps per ball size, for example 4, 5, 6 and 8 mm for the 20 ball, so you can match studs that already exist in the design without turning them again.

In the workshop this kind of ball sits on gear levers, control arms, valve levers and actuators, everywhere a hand has to grip the end of a rod many times per shift. Fixture builders also use them as pull knobs on sliding guards and doors in machine cells. The matte surface gives a good grip even with gloves or oily fingers, and the black color hides dirt and scratches better than glossy surfaces do.

PA6 is one of the most common engineering plastics for a reason. The material is tough, impact resistant and stands up to oils, greases and most of the cleaning agents found around machinery. Nylon takes up some moisture from the air, which in practice makes the part even tougher; for a handle ball that is an advantage rather than a problem, since the load comes in bursts and the dimensional demands are moderate. The density of around 1.14 g/cm³ also makes the ball light, so the lever feels less top heavy than with a knob in steel.

Compared with a threaded knob you avoid threading the end of the stud, and the joint cannot unscrew itself from vibration. The drawback is that the ball is not made to be removed and refitted many times; if the lever has to be taken apart often, a threaded version is a better choice. Press it on straight, preferably in an arbor press, and make sure the stud is free of burrs with a small chamfer on the end that guides it into the hole. Exact tolerances for the stud diameter are in the manufacturer's data sheet.

The balls are supplied by the pack: 500 pieces for the 20 and 25 sizes, 250 pieces for 33 mm and 150 pieces for 40 mm. That suits production setups where the handle is a standard component used up continuously, and works just as well as a spare parts stock in the maintenance department.

Not sure which ball diameter or which hole suits your lever? Get in touch with us and we will help you pick the right version.