Aluminium NEMA17/775 (5mm x 5mm) Rigid Coupling

Prototyping and Engineering Tips from Robogears

• Alignment is Mandatory: CRITICAL: Because this is a Rigid coupling, the motor shaft and the driven shaft must be perfectly aligned (collinear). If there is even a slight offset or angle between the two shafts, a rigid coupler will put immense stress on the motor bearings, leading to premature motor failure or vibration. If your alignment isn't perfect, consider using a "Flexible/Plum" coupling instead.

• The "Flat" Spot Rule: For the most secure connection, ensure that the grub screws sit on the "Flat" part of the D-shaped motor shaft. If your shaft is perfectly round, we recommend filing a small flat spot where the screw will land. This prevents the coupler from spinning freely on the shaft under heavy load.

• Thread Locker (Loctite): In high-vibration environments (like CNC routers), the small grub screws can vibrate loose over time. Apply a tiny drop of Blue Thread Locker to the M4 screws before final tightening to ensure the connection remains permanent.

• Cleaning the Shafts: Before installation, use Isopropyl Alcohol (IPA) to clean any oil or grease off the motor shaft and the inside of the coupler bore. Friction is the only thing holding these together; any lubricant will cause the coupler to slip.

• Testing for Runout: After installation, spin the motor slowly and watch for any "wobble" (runout). If the driven shaft is wobbling, loosen the screws, realign the motor mount, and retighten. A wobbling shaft at 3000 RPM can cause catastrophic mechanical damage to your project frame.

Package Includes

• 1 x Aluminium Rigid Coupling (5mm x 5mm)

• 4 x M4 Grub Screws

Disclaimer: Do not use this coupling if your shafts are not perfectly aligned; the resulting stress can snap motor shafts or destroy bearings. Ensure the grub screws are tightened evenly on both sides to maintain balance. Keep fingers and loose clothing away from the coupling during high-speed operation. Use the correct sized Allen key to avoid stripping the grub screw heads.