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When inspecting fillet welds, if the drawing calls out for 1/4" weld (for example), and the actual weld has leg lengths of 5/16" or 3/8" or even larger, does the weld have to have a throat to match the actual weld legs? Or as long as the throat meets a 1/4" weld, that's enough?
If the fillet is concave you need to use the concave portion of the leaf fillet gage. This is the only commonly used gage that actually measures throat.
If the leg lengths are both larger than the called out weld size and the profile is flat or convex, than the required throat dimension has been met. (assuming fusion at the root)
Also assuming that the weld has already been calculated and called out as the leg length and not the throat. Usually only the engineer makes notes off of their calc sheets that reference the throat dimension. The detailers almost always call out the converted leg lenght dimension. So, all we have to do is measure leg length unless, as Lawrence mentioned, it is a concave fillet weld and not a convex fillet weld.
Question 1 - No.
Question 2 - Yes.
On a tangent to your question... Do you have the chance to observe some of these joints at fit-up? When I see over-sized welds especially on something as small as a 1/4" fillet I always look at (or ask about) the root opening as the called out size gets increased by the root opening. In my world of large fillet welds, some welders have trouble with a 1/4" fillet and always oversize them a bit.
Yes... these are instances where fit up is good. If the weld needs to be oversized, the throat needs to be flat or convex. I'm specifically asking where the legs of the weld are bigger than what's required and the weld is concave.
I agree with Lawrence.
Whether the fillet profile is concave, flat or convex, as long as the call out for a .250" fillet weld meets the .354" throat dimension your leg lengths may be larger that .025".
May I recommend an excellent article titled Tips For Using Fillet Weld Gauges, by Al Moore that was featured in Inspection Trends Jan 2011 Vol 14 No 1.
On a side note, AISC recommends that either or both legs of fillet welds may be oversized without correction, provided the excess weld metal does not interfere with the satisfactory end use of the member. Attempts to remove such excess weld metal may cause shrinkage, distortion, and/or cracking.
Ya know, I think the text of the slide I posted above may be in-part or wholly excerpted from Al's article.
I have him cited as a source in the presentation bibliography but apparently forgot to link it to the page.
Thanks once again Al for helping people learn.
I think this covers the root of the conversation here if I understand it. The leg length may appear correct on a concave fillet, while the throat dimension is insufficient.
This is a condition we must be aware of in my business when placing small SAW fillets at high speeds.
Meaning: If you were to spin that leaf gage around and apply the other side, it would indicate a 1/4" leg length, while the weld is actually unacceptable... So important to know how to use those gages.
Thank you Lawrence.. The root of the issue is the opposite of what you explained. When the throat meets the required dimension, but the legs of the weld are grossly oversized. I only recently questioned this because of some multipass fillet welds where the legs extended much further beyond the required leg length. I started to wonder if this caused a stress in the joint. (Sorry, I'm not able to attach any visual aids)
What you describe is pretty common for CJP T connections that may require a reinforcing fillet eh?
D1 does not have any rejection criteria that I know of for oversized fillets like you describe. EDIT: "unless the oversized fillet interferes with bolting or fit-up" Nonetheless they can cause distortion of base/connection plates or at least make strongbacks necessary when a 'right sized' fillet will not cause distortion at all.
UUMM, welding almost always distorts. Just not beyond any acceptable tolerance and in many cases small enough amounts that it is difficult to see. Depends upon how long the parts and welds are and what sizes the materials are. Even short connection plates and stiffener plates will distort a noticeable amount.
The throat should meet the size of that specified. So regardless of the leg size, the throat must be that of a 1/4" fillet weld. However you can only measure the throat only if the contour is concave.
If the weld is flat or convex on the face, the throat will meet that of the leg size. If the face is concave, the throat has no relationship to the leg size and thus a throat gauge is required.
In some countries and even with some companies here, fillet weld sizes are specified by the throat dimension required.http://www.weldingdata.com/FilletWeldgage.htm
may help but I am not sure. It is in the context of the question.
I think, if the throat meets that of a 1/4" and the contour is concave, the size is met.
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