D1.3 undercut

Date 06-25-2004 10:57

Hi stewnsteve,
The way I read AWS D1.3:98, Paragraph 6.1.1.3 is that the "depth of undercut is not a subject of inspection and need not be measured" (with a v-wac gage). It goes on to say, "melt-through that results in a hole is unacceptable".
I would say that as long as the length doesn't violate the L/8 and there are no melt-throughs that result in holes, any undercut within those parameters is acceptable.
John Wright

By jwright650 (*****)

Date 06-25-2004 11:04

Additionally, if you did use a v-wac gage to measure the amount of undercut you are describing(less than a hair deep), it will probably measure less than what the v-wac gage is capable of measuring. I have thrown that gage on welds I just knew had too much undercut and saw that the gage really didn't show anything. The toe of some welds look deceivingly low when they have that dark slag line.
John Wright

By CHGuilford (****)

Date 06-25-2004 13:25

That portion of the code is really a bit ambiguous.

The 6.1.1 provision says that undercut depth is non relevent but the length is. The "Catch-22" is that because of surface tension of liquid metal, it is almost impossible not to have some undercut on a weld.
So how do you evaluate the L/8 rule? Technically any depth of undercut must be considered for length the way that spec is worded.

I have not seen this addressed anywhere else in D1.3 so my opinion, FWIW is this: Sheet steel is normally governed under the ASTM A6 quality and dimensional requirements. Table 1 in that spec says the allowable thickness variation for plates up to 1/4" thick is 0.03". If the undercut does not reduce the allowable cross section of the material by more than that amount, I would call it irrelevent and not worry about the length.

Again, that is just my opinion so I would check with the customer for their opinion.

Chet Guilford

By CHGuilford (****)

Date 06-25-2004 21:01

It was pointed out to me that my comment might be misunderstood. Table 1 in ASTM A6 shows 0.03 as the thickness tolerance and many guage materials are thinner than that dimension.

What I meant is that if no other undercut depth criteria exists I would regard undercut that is the same as or less than the thickness tolerance as being insignificant. The tolerance would come from the standards that apply to the material, which may not be ASTM A6. Guage materials are not likely to be main tension members in a so a bridge probably won't collapse because of undercut.

But the end use must be considered and the customer should be consulted before applying any personal interpretations.
Chet Guilford