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COLLET FIXTURE KNOBS

A collet-fixing knob uses an internal (usually brass) sleeve that closes around the spindle when a screw or cam mechanism inside the knob body is tightened. Unlike a set screw biting into one point on the shaft circumference, the collet clamps around the full perimeter, distributing the clamping force evenly.

The practical benefit of this is threefold:

  1. Torque transfer is high relative to the size of the fixing, because the whole collet surface is loaded rather than a single point of contact. Typical figures for OKW’s collet-fixed control knobs are an installation torque of around 1.5 Nm and a functional (in-use) torque capacity of around 1.2 Nm. This comfortably covers rotary potentiometers, rotary encoders and touch/click menu functions on consumer and professional equipment.
  2. The fixing is entirely internal so the front-panel appearance stays clean, with no visible screw head or slot to spoil the aesthetic or catch dirt.
  3. Collet knobs are assembled from the front in one motion, with no need to reach behind the panel – and this matters a lot on a production line. That’s a genuine cycle-time advantage on high-volume builds.

The trade-off is cost and complexity. A collet mechanism is a more sophisticated part than a plain knob body, so unit cost is higher than a basic push-on equivalent. Collet knobs are also specified to a particular bore size and spindle diameter, so there’s less tolerance for using the wrong reducing insert than you might assume, and the knob depends on a round or DIN 41591 shaft end to seat correctly.

Where the mechanism is a screw-actuated brass collet, you also need clear rear or axial access for the actuation screw during assembly, even though the fixing itself doesn’t protrude once installed.

Where to use it: menu-driven interfaces, rotary encoders with a push/click function, medical and laboratory instruments, and any high-volume consumer or industrial product where fast front-panel assembly and a tidy appearance both matter. This is why you’ll find it as the default fixing across ranges such as CONTROL-KNOBS, COM-KNOBS and COMBINATION KNOBS spanning ø9 mm to ø50 mm bodies on 3, 4, 6, 8 mm, 1/8" and 1/4" inch spindles.