▭ Slot weld
Slot weld · Soldadura en plano · ISO 1101 + ASME Y14.5
Example in plan
How to interpret it
On the drawing, “Slot 20×8 welded full length” states a slot weld requirement.
What controls
Variant of the plug weld in which the opening in the top plate is an elongated slot instead of a round hole. The symbol is accompanied by the width and length of the slot, its orientation, the pitch if repeated and the depth of filling when it is not complete. It gives more joint area than a plug of the same width and allows that area to be oriented in the direction of the load. Like the plug weld, it joins by filling, not by the perimeter.
How to verify
Calipers for the width and a tape measure for the length and pitch of the slots before welding; visual inspection and, if there is a flush dimension, a depth gauge on the fill. The number of slots is checked against the drawing. Fusion to the bottom plate is demonstrated by a qualified procedure or destructive coupon testing, never solely by what can be seen on the surface.
Common mistakes when interpreting it
- Treating the slot as an assembly clearance slot and cutting it by eye: its dimensions define the load-bearing area of the joint.
- Welding only the ends of the slot and leaving the center hollow: the specified fill is what provides the strength.
- Rotating the slot relative to the drawing because it was easier to cut in the other direction.
How to get it in the workshop / if it comes out of tolerance
The slot is cut or machined beforehand in the top plate; its width and length are functional dimensions, not an approximate opening. Orientation matters: a slot placed at 90° to the one shown changes how the joint behaves. When filling, weld continuously from one end to the other so as not to leave slag between segments.
Slag trapped at the center of the slot: the typical defect of filling in several short passes; clean between passes and run the fill continuously in the same direction. If the slot distorts or closes up during welding, clamp the plates with fixturing before starting. If material stands proud, grind it back without thinning the base plate.
Related symbols
Other symbols in Flat welding
Related tools
ISO fits
Calculates indicative ISO 286 tolerances for shaft and hole, H7/g6, H7/h6, H7/k6 and H7/p6 fits with clearance, transition and interference graph.
Inspection Plans
Upload a plan, extract dimensions and GD&T with AI and export your inspection guideline in PDF or CSV.
Shop trigonometry
Workshop trigonometry: right triangle, C chamfer, Z countersink, sine bar, taper and polar→X/Y for CNC operators.