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LATERAL SCREW FIXING KNOBS

This is the traditional approach: a set screw entering the knob body radially and bearing directly on to the flat or round face of the spindle. A cup-point profile is the usual choice, since it bites into the shaft surface and resists rotation – without the screw wandering off-centre. Our award-winning TOP-KNOBS range gives a typical hex-socket set screw (1.5 mm) with a maximum tightening torque of 40 to 65 Ncm (depending on knob size) across a body diameter range of ø16 mm to ø40 mm.

Lateral screw fixing offers a number of advantages. It’s mechanically simple and inexpensive to produce – and it can be re-tightened repeatedly without wearing out the clamping mechanism. And because the screw contacts the spindle directly rather than through an intermediate sleeve, it can be specified with generous torque margins on more traditional, heavier-duty knob bodies.

Set against that, the screw head is, by definition, on the outside of the knob, which is a cosmetic and safety consideration. Our design answer to this on ranges such as TOP-KNOBS is a separate arrow or marking disk that is clipped on to the knob afterwards, hiding the screw completely and removing any risk of accidental contact with a live shaft. That’s a sound detail to specify if you go this route but it does add an assembly step and a component.

You’ll also need side access to the knob for a hex key during assembly and any subsequent service. This is a constraint on densely packed panels, and a set screw biting into a single point on the shaft carries a higher risk of marring a soft-shaft potentiometer over repeated fitting and refitting than a collet’s distributed clamp.

Vibration is worth a design check too: a point-contact fixing is more prone to working loose under sustained mechanical vibration than a full-perimeter clamp, so a thread-locking compound is worth considering in vibration-heavy applications such as vehicle or plant equipment.

Where to use it: classic-styled instrument and control panels; equipment needing a metal-cap or insert-embellisher esthetic; higher-torque manual controls; applications where thermal stability outweighs the cosmetic and assembly-access downsides of an external screw.