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A translator posted this diagram of a weld joint on a translator's forum (the figure below). What does the abbreviation "B.C." mean on the diagram?

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I'm not aware of BC as standard English nomenclature for welding, but I have a guess for what they mean. The fact that there is a period after the B but not the C makes me wonder if something was cut off or whited out in the original.

I think they mean backgouge (BG) which would be a common process in a double sided vee groove weld it it needed to be a complete joint penetration (CJP) weld. This is sometimes indicated with a dotted line like that, although strictly of they backgouge as shown they should have drawn a u groove weld instead of a vee groove on the top side.

There welder will bevel the bottom side using a grinder or plate beveler. Then they will weld the bottom side, but the root of the bottom weld will be contaminated by air from the other side of the weld since there is no backer or backing gas and thus no shielding on the far side. On the top side, using a grinder or a carbon electrode they will remove all of the contaminated root metal and then begin the seconds side weld. This weld if protected on the back side by the metal of the first weld, yielding a sound weld through the whole depth of the joint.

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  • $\begingroup$ Thank you! A translator in the forum said it might be "back chipping". $\endgroup$
    – CopperKettle
    Sep 6, 2016 at 9:04
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    $\begingroup$ @CopperKettle that could be right too, chipping is an acceptable method of backgouging. I'm not aware of anyone who actually does it in the US, but the economics may be appealing in other places. $\endgroup$
    – Ethan48
    Sep 6, 2016 at 11:25
  • $\begingroup$ It seems unlikely that anything was whited out given that the single period is consistent in the two images added since you answered and one of them is typed rather than handwritten. The image of the table makes me wonder if it's actually just some kind of placeholder along the lines of "TBD" that's been translated literally and has no cognate. $\endgroup$
    – Air
    Sep 7, 2016 at 15:00
  • $\begingroup$ Yeah, or I could also see the thought process to only put a period after the B. C (without a period) is the standard annotation for chipping when you're talking about contouring reinforcement on a weld (G for grinding, M for machining, etc.) so whoever drew this may have thought "Abbreviate 'back' to B, and C already means chip." $\endgroup$
    – Ethan48
    Sep 7, 2016 at 15:14

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