View Full Version : Does anyone understand this weld symbol?

02-06-2009, 10:02 AM
Does anybody understand this symbol. I cant figure out the letter T in the backing bar . I also dont see a groove depth and is the 3/16 / 45 the cap fillet? Im confused
Thanks for any help.:)


02-06-2009, 10:36 AM
I think you will need some clarification from the designer.

The "T" may represent temporary backing that would be later removed.

The 45 to the right of the fillet symbol is non standard. The intent may have been to include the 45 as the groove angle.

Because no depth of preparation or weld throat is specified, the groove shall extend through the thickness of the joint and the weld throat shall be equal to that thickness.

This is based upon the AWS Welding symbols. The europe standards may be different.

02-06-2009, 11:11 AM
The weld symbol is for a groove weld but points to a fillet joint on the print.

To me, the info on the flag on the weld symbol indicates a 3/16" fillet leg length and the 45* indicates a 45 degree fillet face to leg angle, which is standard for a fillet weld.

The tube appears to be 7" outside diameter with a 3/8" wall thickness, which would explain the 3/16" fillet leg size clarification on the weld symbol, since standard fillet leg length would be 3/8" for a 3/8" thick tube welded to a 1/2" thick flange.

Why there would be a temporary backing bar behind a fillet joint I have no idea. That part makes no sense to me. There doesn't appear to be any place to put a temporary backing bar on the joint in the drawing. Possibly the 1/4" thick plate that fits inside the tube is what the 'T' is referring to on the weld symbol? Maybe that's being used a backing ring, or is it part of the finished part?

02-06-2009, 11:25 AM
Reading from the reference line:

Side opposite arrow:
slot coverage at root (not sure about the T)

On arrow side:
Groove weld, single bevel (the tube end gets the bevel)
followed by a 45 deg fillet weld with 3/16 legs

see http://www.welding.com/weld_symbols_welding_symbols.shtml

02-06-2009, 11:53 AM
I don't know weld symbols well so won't even try to discuss that, but the diagram indicates to me that the flange has been machined from thicker stock, leaving the raised collar improperly labeled a 'rolled pl'. for both locating and structural purposes.

02-06-2009, 12:43 PM
The notation of DEGREE for a fillet weld is not a standard weld symbol.

If the weld were to be anything besides 45 degrees it would be addressed as an unequal leg fillet with dimensions to the left of the symbol indicating each leg size.

02-06-2009, 05:48 PM
To me, this welding symbol shows a piece of 1 1/2" plate with a 3/8 piece of aluminum tube being welded to it. They have it all jacked up though. Whenever you use a broken arrow with a welding symbol, the plane which the arrow points to is the side that recieves the joint preparation. In this case that would be the plate. How can you put a bevel in the middle of a plate? You can't! Simple mistake though. The arrow (if broken) which this one is, should be pointing to the tube. The tube according to this drawing is to be beveled on the arrow side at an angle of 45 degrees. The groove is to be welded so that no underfill is present, then a fillet weld ( a 3/16" leg size reinforcing fillet weld) is to be deposited over the groove weld. But this fillet weld size cant be correct either. If you bevel a piece of metal which is 3/8" thick, fill the groove then reinforce the joint with a 3/16" fillet weld, you will still have an area above the reinforcing (3/16" to be exact) where the groove weld is still showing. As far as the backing goes, I have never seen the letter T inside or the backing strip. Only R which stands for remove or M which stands for material. The material should be listed in the tail of the symbol. I agree that maybe they want it to be temporary?? I think you should "have a little talk" to whoever wants you to weld this joint like this. The reinforcing fillet weld should be a minimum of 3/8" due to joint design. Ive seen worse symbols than this though. Here is your typical guy drawing welding symbols......

02-06-2009, 06:07 PM
Oh yeah when no depth of preparation and no weld size is listed on the reference line that weld is to be made complete joint penetration. Im also surprised there is no root opening listed. It has to be some form of nonmetallic backing....maybe it stands for tape. Glass tape is a popular form of backing.

02-06-2009, 09:57 PM
I want to thank everyone for their responses. This joint came from state engineering firm. The products we are building are hi way related. I am new to the forum and am amazed at all the very intelligent replies to my thread.Nice to see a bunch of people helping people.

02-07-2009, 02:06 PM
hi mike,
gerald was correct in the 'T' meaning temporary for the backing strip. the actual correct symbol is an 'R' in the block, meaning remove after welding. also, the backing strip should have a notation either in the tail or on the print stating what kind of backing was to be used.
see ya,

02-07-2009, 08:02 PM
whups, el lloydeo already had it covered. sorry about that. i'm always late to the party!