Resistance spot welding — recommended edge distance For a satisfactory spot weld near an edge, the minimum distance from the nearest sheet edge to the centre of the weld nugget should be approximately:

Introduction / Context:In resistance spot welding, electrode indentation, current density, and heat flow must be balanced to create a strong nugget without edge burn-out or expulsion. Proper spacing from edges prevents molten metal from escaping and ensures adequate current paths.

Given Data / Assumptions:

• d denotes the weld nugget diameter or, in practice, the electrode face diameter used for sizing.
• Sheets of comparable thickness are being welded.
• Standard shop guidelines are applied for mild steel.

Concept / Approach:The minimum edge distance is set to keep sufficient surrounding material to contain the nugget and provide adequate current and force distribution. A commonly used rule is edge distance ≈ 1.5 d to 2 d for steels. At this spacing, the risk of edge expulsion, undersized nuggets, or severe indentation is reduced, while still allowing welds close to flanges or corners.

Step-by-Step Solution:Relate edge distance to nugget size: choose a factor that ensures containment of the fusion zone.Select the lower standard bound: 1.5 d is widely accepted as a minimum.Hence, the recommended value is 1.5 d.

Verification / Alternative check:Automotive and appliance welding schedules typically specify 1.5 d to 2 d; destructive peel tests near edges confirm sufficient strength at these spacings.

Why Other Options Are Wrong:

• d or 0.75 d: too close; causes edge burning, expulsion, and weak nuggets.
• 3 d or 6 d: acceptable but unnecessarily conservative for most designs, reducing layout efficiency.

Common Pitfalls:Confusing pitch (spacing between adjacent welds) with edge distance; the pitch is often 3 d to 6 d, not the edge distance.

Final Answer:1.5 d