Spiral Beam Couplings.

What are Spiral Beam Couplings?

Beam couplings are flexible shaft couplings machined from a single piece of material, with one or more helical (spiral) cuts running through the body. Those cuts let the coupling flex just enough to take up angular shaft misalignment, while the one-piece construction keeps it zero backlash, so there is no lost motion between the driving and driven shafts. That combination makes beam couplings a compact, accurate choice for connecting small motor, encoder and feedback shafts in precision motion systems.

How Helical Beam Couplings Work

A beam coupling flexes through the helical slit machined into its body. As torque is applied, the spiral cut allows a controlled amount of bend so the coupling accommodates angular misalignment between two shafts, yet it winds up very little, which is what gives the zero-backlash, constant-velocity behaviour designers rely on for positioning accuracy. Because the coupling is a single machined part with no separate insert or elastomer element, there is nothing to wear out or replace. The balanced one-piece body also runs true at high speed, rated up to 70,000 RPM.

Take an optical encoder reading a small servo shaft: a beam coupling links the two so the encoder tracks true angular position without backlash, even if the shafts sit slightly out of line. Where an application needs to damp vibration rather than hold precise position, a rubber-core high-gain coupling is the softer alternative; beam couplings are the stiffer, zero-backlash choice. 

Materials Beam Couplings Are Made From

Accu's beam couplings are machined from a single, lightweight aerospace alloy:

• Aluminium - Aerospace (Grade 7075): a high-strength, lightweight aluminium with a SurTec 650 passivated finish for corrosion resistance, keeping mass and rotational inertia low for the fast, frequent direction changes of servo and encoder drives.

Sizes and Types of Beam Couplings Available

Accu's beam couplings are the compact Reli-a-Flex Micro range, built for miniature drives. Bore sizes run from 1.5 to 5 mm, outside diameters from 6 to 10 mm and overall lengths from 9.35 to 17 mm, across 18 configurations. The small envelope suits encoder, tachometer and low-torque servo or stepper connections where space is tight and positioning accuracy matters. Every coupling is a one-piece helical-cut design, so the type is consistent across the range; you select on bore, outside diameter and length to match your shafts and space.

FAQs

Q: Are beam couplings zero backlash?

A: Yes; the single-piece helical construction transmits torque with no lost motion, which is what makes them suited to precise positioning and feedback.

Q: What is the difference between a beam coupling and a jaw coupling?

A: A beam coupling is one machined piece with helical cuts, whereas a jaw coupling is a three-part assembly with a replaceable elastomer spider between two hubs.

Q: What sizes do beam couplings come in?

A: The current Reli-a-Flex Micro range covers bores from 1.5 to 5 mm and outside diameters from 6 to 10 mm.

Q: What are beam couplings used for?

A: They connect small motor, encoder and feedback shafts in miniature servo and stepper assemblies where zero backlash and positioning accuracy matter.

Q: What material are beam couplings made from?

A: Accu's beam couplings are machined from aerospace-grade aluminium (Grade 7075-T6) with a Surtec 650 passivated finish.

Bespoke Spiral Beam Couplings Manufacture.

High precision, bespoke manufacture of Spiral Beam Couplings to customer specification. State of the art facilities specialising in both small batch prototyping and large scale manufacture.