Which joint feature improves alignment and strength in spin-welded assemblies?

• A. Flat surfaces with no alignment features.
• B. A simple butt joint without alignment aids.
• C. An oversized clearance fit.
• D. Interlock or collar joint features that improve alignment.

Answer: (D)

In spin welding, keeping the parts properly aligned as they spin under pressure is essential for a strong, uniform weld. Interlock or collar joint features act as physical guides that lock the parts in the correct orientation and prevent unwanted movement during rotation. This ensures the contact surfaces remain concentric and the heat is generated evenly along the intended seam, producing a more consistent and stronger bond.

Without alignment features, flat surfaces can drift or tilt during spinning, leading to eccentric rotation, uneven heating, and a weaker weld. A simple butt joint without alignment aids has no locating geometry to keep parts aligned, so misalignment is likely and strength suffers. An oversized clearance fit introduces looseness, allowing wobble and poor heat transfer, which also degrades the weld quality.

Therefore, interlock or collar features are the best choice for improving both alignment and strength in spin-welded assemblies.