Introduction
Servo drives, CNC spindles and precision positioning axes place different demands on shaft couplings than general industrial pump or fan duty. Engineers typically evaluate backlash, torsional stiffness, inertia and misalignment together with torque and speed.
This application guide routes servo and CNC duty toward disc and bellows technologies represented on Golden Bearing Company. It complements the Disc Coupling Selection Guide and Bellows Coupling Selection Guide. Catalogue torque, stiffness, backlash and speed ratings are manufacturer-specific — confirm on each family page before ordering.
Servo drive requirements
| Requirement | Engineering consideration | Why it matters |
|---|---|---|
| Backlash | Lost motion between input and output rotation | Positioning accuracy and reversal error |
| Torsional stiffness | Resistance to angular deflection under torque | Control loop stability and settling time |
| Inertia | Coupling mass relative to motor and load inertia | Acceleration response in high-dynamic axes |
| Misalignment | Residual angular, parallel and axial offset | Bearing load and element life |
| Speed | Operating and maximum RPM | Balance and critical speed on small bores |
Servo applications often favour metal disc or metal bellows couplings over soft elastomeric designs because elastomer wind-up can limit positioning performance. Elastomeric couplings may still suit damping-heavy stepper or light-duty axes — compare application requirements before excluding a technology.
Technology routing
| Application signal | Consider first | GBC routing |
|---|---|---|
| High torsional stiffness, defined disc pack | Disc coupling | KTR RADEX-NC, Miki Servoflex |
| Low backlash, compact precision connection | Bellows coupling | KTR TOOLFLEX S, R+W bellows |
| Moderate precision with damping | Elastomeric (limited) | Compare only if positioning tolerance allows — see elastomeric guide |
| Very high torque precision duty | Review disc and gear options | Compare governed catalogues; gear coupling maintenance differs |
GBC family routing
| Family | Technology | Typical servo/CNC context | Hub |
|---|---|---|---|
| KTR RADEX-NC | Disc | Servo drives requiring disc pack stiffness; EK/DK configurations | KTR couplings |
| Miki Servoflex | Disc | Metal disc couplings for servo and stepper positioning | Miki Pulley couplings |
| KTR TOOLFLEX S | Bellows | Metal bellows for servo and precision machinery | KTR couplings |
| R+W bellows | Bellows | BK and BKL families for encoder and CNC duty | R+W couplings |
Listing families in this table does not mean they are interchangeable with each other.
Configuration considerations
- Single-flex vs double-flex disc — affects misalignment accommodation and bearing loads; compare Servoflex SA2/DA2 variants on the Miki family page.
- Clamping vs setscrew hubs — shaft retention method affects bore sizing and high-speed duty; confirm on catalogue.
- Spacer length — rarely required on compact servo axes; confirm machine envelope before specifying DBSE.
- Torsional stiffness basis — configuration-specific values (e.g. RADEX-NC DK basis) must not be generalised across sizes or families.
Duty checklist
- Confirm continuous and peak torque at operating speed.
- Define backlash and stiffness targets from machine builder or control supplier where available.
- Measure bores — motor and load shaft diameters, keyways, hub style.
- Estimate misalignment — angular, parallel and axial after assembly.
- Shortlist disc or bellows family — open governed catalogues for torque, speed, bore and stiffness data.
- Compare envelope — outside diameter, overall length and guard clearance.
- Request quotation — send axis configuration and duty data through engineering enquiry.
Next steps
- Review disc and bellows technology guides.
- Open the family catalogue that best matches your stiffness and backlash requirements.
- Compare governed size, torque, bore and speed data for shortlisted models.
- For broader technology context, return to the Industrial Coupling Selection Guide.
Scope and limitations
- This article provides servo/CNC application routing only; family pages own catalogue data.
- Numerical stiffness, backlash and torque ratings must come from manufacturer catalogue or product record data.
- No cross-brand equivalence or superiority claims are made in this guide.
- R+W products are offered as dealer/stockist catalogue support — confirm availability at quotation.