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When misalignment between a servo motor shaft and a driven component causes vibration, noise, or premature bearing wear, the root cause is often a rigid or worn coupling. Engineers, CNC builders, and automation technicians who need reliable torque transmission with angular and axial compensation rely on a diaphragm-style flexible coupling to absorb those deviations without sacrificing rotational accuracy.
This D68 single diaphragm shaft coupling is machined from aluminium alloy and measures 68mm in outer diameter (OD) × 54mm in length (L54mm). The two-hub design accepts bore sizes from 12mm up to 35mm (approximately 0.47" to 1.38") on each side, with both equal and unequal bore combinations available across the variant range. The single diaphragm flexing element transmits torque while accommodating angular misalignment typically up to 1°–2° and axial displacement.
Typical applications include CNC router and milling machine Z-axis ballscrew drives, servo motor to encoder shaft connections, rotary indexing tables, and light-duty industrial automation where zero-backlash torque transmission is required. The aluminium construction keeps rotating mass low, making it well-suited for high-speed servo and stepper motor pairings.
| Outer Diameter (OD) | 68mm (2.68") |
|---|---|
| Body Length | 54mm (2.13") |
| Bore Size d1 | 12mm – 35mm (see variant options) |
| Bore Size d2 | 12mm – 35mm (see variant options) |
| Coupling Type | Single Diaphragm Flexible |
| Material | Aluminium Alloy |
| Angular Misalignment | Typically 1° – 2° |
| Backlash | Zero (diaphragm element) |
| Hub Style | Split Clamp |
| Weight | See variant options |
| Finish | See variant options |
Measure the shaft diameter on your motor side (d1) and your driven component side (d2) using a digital calliper. Both values must fall within the 12mm–35mm range offered by this coupling. Select the variant that matches your exact d1 and d2 combination — equal bores (e.g. d12×d12) and unequal bores (e.g. d12×d35) are both available. If your shaft has a tolerance fit, choose the bore that matches the nominal shaft diameter.
The torque rating of a single diaphragm coupling depends on the diaphragm thickness, material, and bore configuration. For this D68 aluminium coupling, the rated torque is typically in the range suitable for servo and stepper motor applications in CNC and light automation. Contact us to confirm the rated torque for your specific bore combination before use in high-load applications.
Yes. The aluminium alloy construction keeps rotational inertia low, which is important for servo systems that require fast acceleration and deceleration. The single diaphragm design provides zero backlash and torsional stiffness, making it well-suited for servo motor to ballscrew or encoder shaft connections. Verify the maximum RPM rating with us if your application exceeds 3,000 RPM.
Yes. The single diaphragm flexing element is designed to accommodate angular misalignment typically up to 1°–2° and a small degree of axial displacement. It is not intended to compensate for large parallel (radial) offsets. For best results, align your shafts as accurately as possible during installation — the coupling handles residual misalignment, not gross alignment errors.
This coupling uses a split-clamp hub design that grips the shaft by clamping force when the clamp screws are tightened. No keyway is required for standard servo motor shafts. If your shaft has a flat or keyway, the clamp will still function, but ensure the bore is the correct size for a proper fit. Do not over-tighten the clamp screws beyond the recommended torque for the fastener size.
A single diaphragm coupling uses one flexible disc element between the two hubs. It handles angular misalignment and axial displacement well but has limited parallel offset compensation. A double diaphragm coupling uses two disc elements with a spacer, providing greater misalignment capacity in all directions. For most CNC servo motor applications where shafts are well-aligned, a single diaphragm coupling is sufficient and more compact.
Aluminium alloy has natural oxidation resistance that provides moderate protection against humidity and light moisture exposure. For environments with direct water exposure, chemical splashing, or salt air, consider applying a protective coating or selecting a stainless steel coupling. For standard indoor CNC and automation environments, the aluminium construction is appropriate without additional treatment.
