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When misalignment between a motor shaft and a driven shaft causes vibration, premature bearing wear, or encoder signal drift, the root cause is almost always an inadequate coupling. Engineers and machine builders who demand zero-backlash torque transmission need a coupling that absorbs angular and parallel offset without sacrificing rigidity — and that is exactly what these parallel slit flexible shaft couplings are designed to deliver.
Each coupling is machined from a single billet of aluminum alloy, featuring a parallel slit pattern that creates controlled flexibility along the coupling body. Available in three outer diameter series — D16 × L23 mm (0.63" × 0.91"), D19 × L25 mm (0.75" × 0.98"), and D20 × L25 mm (0.79" × 0.98") — with bore sizes ranging from 3 mm to 8 mm (0.12"–0.31") on each side. Clamping is achieved via set-screw or split-clamp style depending on variant; bore combinations are selectable at checkout.
Typical use cases include servo motor to ball-screw coupling on CNC routers and milling machines, encoder shaft coupling on stepper motor assemblies, and precision motion coupling on 3D printer Z-axis drives. Long-tail search terms this product addresses: "parallel slit coupler 5mm to 6mm", "D16 flexible coupling CNC", "zero backlash encoder coupling aluminum".
Machined from one billet — no joints, no glue, no assembly play. Delivers consistent torque transmission and long service life.
The parallel slit pattern provides torsional flexibility while maintaining near-zero rotational backlash — critical for encoder feedback accuracy and CNC positioning repeatability.
Choose the outer diameter that fits your motor housing clearance. Each series covers a defined bore range (3–6.35 mm for D16/D19; 4–8 mm for D20).
Absorbs angular misalignment (typically up to 1°) and parallel offset between shafts, reducing stress on motor bearings and encoder housings.
Aluminum construction keeps rotational inertia low — ideal for high-speed servo and stepper applications where rapid acceleration and deceleration are required.
Order 1, 2, 3, 10, 12, or 20 pieces per SKU. Bulk packs reduce per-unit cost for production builds, repair kits, or workshop stock.
| Product Type | Parallel Slit Flexible Shaft Coupling |
|---|---|
| Material | Aluminum alloy |
| Available OD × Length | D16 × L23 mm / D19 × L25 mm / D20 × L25 mm |
| Bore Size Range (d1 / d2) | 3 mm – 8 mm (0.12" – 0.31"); see variant options for specific combinations |
| Bore Combination | Same bore (rigid) or mixed bore (reducing); see variant options |
| Slit Pattern | Parallel slit (single-body flexure) |
| Backlash | Near-zero (torsionally stiff, laterally flexible) |
| Angular Misalignment Tolerance | Typically ≤ 1° |
| Parallel Offset Tolerance | See variant options |
| Surface Finish | Natural aluminum / anodized (see variant options) |
| Quantity per Order | 1 / 2 / 3 / 10 / 12 / 20 pcs (selectable) |
Select based on the clearance available around your motor shaft and the torque requirement. D16 × L23 mm suits compact NEMA 17 setups and light-duty encoders. D19 × L25 mm is a mid-range option for standard servo and stepper applications. D20 × L25 mm handles slightly higher torque and accommodates bore sizes up to 8 mm, making it suitable for larger NEMA 23 motors and ball-screw assemblies.
Match d1 to your motor shaft diameter and d2 to your driven shaft (ball screw, encoder, lead screw) diameter. For example, if your stepper motor has a 5 mm shaft and your lead screw has a 6 mm shaft, select the d1=5 / d2=6 variant. Same-bore variants (e.g., d1=d2=5 mm) are available for identical shaft diameters. The variant selector on this page lists all available combinations.
The parallel slit design is torsionally stiff, meaning rotational play (backlash) is near-zero under normal operating loads. This makes them suitable for closed-loop servo systems and encoder feedback applications where positional accuracy matters. Note that all flexible couplings exhibit some micro-deflection under load — for ultra-precision applications requiring absolute zero deflection, a rigid coupling may be more appropriate.
Aluminum alloy offers good natural corrosion resistance suitable for indoor CNC, 3D printing, and automation environments. If your application involves moisture, coolant mist, or outdoor exposure, consider applying a light coating of machine oil or selecting an anodized variant where available. For highly corrosive environments, stainless steel couplings may be more appropriate.
NEMA 17 motors typically have a 5 mm output shaft — select any variant with d1=5 mm. NEMA 23 motors commonly use 6.35 mm (1/4") shafts — select d1=6.35 mm variants. Always verify your specific motor's shaft diameter in its datasheet before ordering, as some manufacturers use non-standard shaft sizes.
A standard 3-axis CNC router or 3D printer typically requires 1–3 couplings (one per axis). For a production build or workshop stock, the 10-pack or 20-pack options offer a lower per-unit cost. The 2-pack and 3-pack options are ideal for small builds or keeping a spare on hand. Select your quantity in the QTY option above.
Yes. Many variants offer mixed bore combinations (e.g., d1=4 mm / d2=6 mm), allowing you to connect a smaller motor shaft to a larger driven shaft or vice versa. Browse the OD × Length / d1–d2 variant selector to find the combination that matches your application.
