What is the recommended fill depth for plug or slot welds when material thickness is under 5/8 inch and when it is 5/8 inch or more?

• A. 5/8 and under the minimum thickness shall be equal to the thickness of the part; 5/8 and over shall be 0.5 times the thickness but not less than 5/8
• B. 5/8 and under the minimum thickness shall be 0.5 times the thickness; 5/8 and over shall be the thickness
• C. 3/8 and under shall be equal to the thickness; 3/8 and over shall be 0.5 times the thickness
• D. 5/8 and under shall be 0.75 times the thickness; 5/8 and over shall be 0.5 times the thickness

Answer: (A)

When deciding how deep to fill a plug or slot weld, the goal is to provide enough weld metal to fuse the sheets reliably while keeping heat input and distortion in check.

For thicknesses under 5/8 inch, the recommended depth is to fill to the full thickness. This ensures the weld penetrates and fuses through the entire thickness of the sheet, giving solid joint strength on thinner parts without trying to overbuild the weld.

For thicknesses 5/8 inch or more, the guideline shifts to about half the thickness, but with a minimum of 5/8 inch. This keeps the weld from becoming too light in very thick sections, while avoiding excessive weld metal that could cause heat-related problems. In practical terms, if half the thickness would be less than 5/8 inch, you use 5/8 inch; if half the thickness is greater than 5/8 inch, you use that half-thickness value.

So, under 5/8 inch, fill depth equals the thickness; at 5/8 inch or more, fill depth is 0.5 times the thickness, but not less than 5/8 inch.