bevel weld detailing

[rllo]

I have a question about beveling specifically. a 1/4" bevel weld was called out to attach a HSS16x16x1/2 to PL. the shop drawings show a 3/8" chamfer (bevel?) on all 4 sides. why is that? I drew this up in CAD and don't see where my 1/4" bevel spec is. then I realized I don't really know what I'm doing - is the 1/4" bevel supposed to be the leg or hypotenuse distance, I wondered. this is why i'm here. thank you for your help.

 

[kingnero]

Depens on the welding process that will be used and the desired penetration.
A 45° prep is usually to small. Try to have "beta" between 50 and 55°.
My interpretation of the weld designation is 1/4" flat "in" the vertical part, and a fillet weld following on the first weld with a leg length of 1/4".
Hence the 3/8 chamfer, to ensure the weld goes to 1/4" deep. You foresee insufficient penetration this way...

 

[gtaw]

It depends on what your governing standard is. As indicated by the welding symbol you included in your post, the 1/4-inch dimension is the depth of the bevel. For the bevel, the depth would be measured through the thickness of the part being beveled. If AWS D1.1 is the governing standard, the maximum weld size for design purposes would be the depth of the bevel minus 1/8-inch for bevel angles less than 60 degrees.

If the designer requires a 1/4-inch weld size (joint penetration), the 1/4-inch dimension should be denoted as (1/4) [enclosed by brackets]. The depth of the bevel would have to be increased to produce the 1/4-inch weld size if partial joint penetration is expected.

Be aware that AWS D1.1 does not consider a weld made without backing or back gouged to be prequalified. To make a weld without backing or back gouging, it is considered partial joint penetration. The contractor would have to qualify the WPS and the welders without backing in order to comply with AWS D1.1.

Whether the weld is partial joint penetration or complete joint penetration determines the allowable stress permitted and the required weld size.

If you are working to a different fabrication standard, they could have something different.