SCS08 Aluminum Shaft Collar – 8 mm Bore, OD 30 mm Single Split Clamp Ring

When a 6 mm collar simply does not offer enough clamping wall, engineers reach for the SCS08 shaft collar. Designed around an 8 mm bore, the SCS08 jumps to a 30 mm outer diameter, delivering a wall thickness of 11 mm — nearly triple the bore radius — and creating a significantly larger contact surface that can resist both static axial loads and the pulsating forces common in stepper-motor-driven positioning systems.

The SCS08 introduces the 1.5 mm slit gap that becomes standard across the mid-range of the SCS series. This wider slit allows greater collar deflection during installation, making the assembly process faster even when a lubricant film is present on the shaft, while still providing ample closure force once the M4 socket-head screw is torqued to specification.

SCS08 Technical Specifications

Engineering Advantage: OD-to-Bore Ratio

One of the most overlooked selection criteria when specifying shaft collars is the outer-diameter-to-bore ratio. A higher ratio means more material around the bore, which translates directly into higher radial stiffness under clamping load and better resistance to the collar distorting under side thrust. The SCS08 achieves a ratio of 3.75 (30 ÷ 8), placing it among the highest in the series relative to bore size — comparable performance can otherwise only be found in larger, heavier collars on wider shafts.

This geometric advantage makes the SCS08 particularly suitable for applications where the shaft experiences both axial positioning loads and radial guide forces, such as linear guide rod end-stop configurations and NEMA 17 / NEMA 23 stepper motor output shafts common in CNC and 3D printing gantry systems.

Industry Applications: Where the SCS08 Performs Best

▶ Small-Format CNC and 3D Printing

The 8 mm shaft diameter is ubiquitous in desktop CNC router Z-axis lead-screw support bearings, 3D printer Y-axis linear rod systems, and laser cutter gantry guide rails. Fitting an SCS08 at the travel limit of each rod eliminates the need for machined hard stops or custom endplates, and the aluminium construction adds negligible mass to what are often weight-sensitive moving assemblies.

▶ Reduction Gearbox Output Positioning

Small DC gearmotors and planetary gearboxes in robotics joints frequently output via 8 mm shafts. An SCS08 placed between the gearbox face and the driven component (encoder disc, pulley, or coupling hub) creates a precise axial datum, preventing the component from walking toward the gearbox under thrust reversals. This is particularly critical in collaborative robot arm joints where repeated reversals generate cumulative axial drift in poorly fixed components.

▶ Conveyor and Feeder Sub-assemblies

Lightweight conveyor frames in food processing and pharmaceutical packaging environments increasingly specify aluminium collars to comply with weight-reduction initiatives and food-safe material requirements. The SCS08's all-aluminium construction and smooth exterior profile minimise bacterial harbourage points, and its tool-accessible clamping screw allows rapid cleaning-in-place repositioning during changeovers.

SCS08 vs SCS06: Choosing the Right Small-Bore Collar

Both the SCS06 and SCS08 share the same 10 mm width and M4 clamping screw, making them dimensionally similar in the axial direction. The primary differentiation is bore size (6 vs 8 mm) and slit width (1 vs 1.5 mm). If your shaft is 8 mm and your application involves any form of dynamic loading — reciprocating linear motion, motor torque reaction, or variable thermal cycles — the SCS08 is the correct choice. For purely static positioning on lightweight 6 mm precision shafts, the SCS06 may be evaluated as a lighter alternative.

Mounting Recommendations for SCS08

• Shaft tolerance: Specify h7 or h6 shaft tolerance for the 8 mm diameter to achieve the tightest fit within the collar bore and minimise concentricity error.
• Screw torque: Recommended M4 socket-head cap screw tightening torque is 2.5–3.0 N·m. Always use a torque wrench — finger-tight plus a quarter-turn is insufficient for dynamic applications.
• Lubrication: Apply no lubrication to the shaft surface within the clamping zone — friction grip depends on a clean, dry interface. Lightly lubricate the screw thread to avoid galling on tightening.
• Paired installation: Where the SCS08 is used as a bilateral axial stop (one collar per side), equalise tightening torque on both collars before final torque-down to prevent differential clamping that skews the component.
• Re-inspection interval: In vibration-intensive environments, inspect clamping torque every 500 operating hours or per your maintenance schedule, whichever is sooner.

For applications requiring both axial positioning and torque transmission on 8 mm shafts, consider pairing the SCS08 with a keyway-equipped coupling hub. Reach out via the EP contacts page to discuss custom keyway machining or modified slit geometry for high-torque drive systems.

Frequently Asked Questions – SCS08