Encoder Beam Couplings – Zero Backlash Helical Couplings for Servo & CNC Systems

When you’re working with encoders or servo-driven systems, even a small amount of backlash or movement in the coupling can lead to positioning errors, vibration, or inconsistent feedback.

AROFLEX encoder beam couplings are designed to avoid that. They give you a solid, backlash-free connection between shafts while still allowing for a bit of flexibility to take up misalignment, which is what you need in most real-world setups.

This AF25-6-8 is supplied with Ø6mm to Ø8mm bores and a 25mm outer diameter, making it well suited to smaller motors, encoders and compact assemblies where space is limited but accuracy still matters. On this coupling size, the maximum bore available is Ø11mm. If you need a bore size that isn’t listed as standard, we can machine bespoke bore sizes to suit your shaft requirements, typically on a 3–5 working day lead time.

Each coupling is machined from a single piece of aluminium with a helical (spiral) cut. Because it’s one piece, there are no moving parts or inserts to wear, so you don’t get the play you see in other designs. At the same time, the beam cut allows it to flex slightly to take up angular, radial and axial misalignment without putting stress back into the system.

We supply these with precision-machined H7 bores as standard. In practice, that means a more consistent fit on the shaft, less chance of micro-movement, and better overall stability, especially important on higher speed or more sensitive encoder applications.

With an overall length of 32mm, M5 clamping screws, and a rated torque of 2.5 Nm, this size is typically used on light-duty precision drives where low inertia and accurate signal transmission are more important than high torque capacity.

Key Features

• Zero backlash (one-piece design)
  No joints or inserts, so no play under reversal.
• Good torsional response
  Minimal wind-up, helping maintain accurate encoder signals.
• H7 precision bore
  Machined concentrically for a consistent shaft fit, improved running accuracy and reduced vibration.
• Compact and lightweight
  Ideal for smaller motors, encoders and tight installations.
• Handles misalignment
  Takes up angular, parallel and axial misalignment without introducing play.
• Clamp hub design
  Secure 360° grip on the shaft without the need for keyways.
• Maintenance-free
  Nothing to wear out or replace.
• Bespoke bore machining available
  Standard and custom bore sizes available up to Ø11mm on this coupling size, with bespoke machining typically available in 3–5 working days.

Typical Applications

• Encoder to motor connections
• Servo-driven systems
• CNC axes and positioning equipment
• Robotics and automation
• Stepper motor setups
• General precision machinery

You might also see these referred to as helical couplings, slit couplings, or flexible beam couplings – they’re all the same basic design.

One thing to be aware of: beam couplings aren’t designed for high torque. If you need more rigidity or torque capacity, a bellows or disc coupling may be a better option. But for encoder work and lighter-duty precision applications, this size offers a simple, reliable solution.

In short: compact, accurate, and easy to install — a good fit where you need zero backlash without overcomplicating the setup.