"Maxwell" wrote in
:


edge of the weld touching the beam is .01 inch)
· Undercut shall be no more than 1/32 inch deep for all other cases


Thanks, that's what i needed to know OK. But from a practical
standpoint, is it normal to have such an undercut on a weld? I would
imagine undercut would be a stress riser, for starters.


I was hoping someone would come along with some solid data on this
one, but if you are talking about an aircraft weld, I hesitate to
think ANY undercut should be acceptable.

Are you welding tubing or plate? Aluminum or steel? Gas, stick, mig or
tig?

Usually, undercut is caused by a combination of factors. Weld speed,
deposit rate and weld position, are common factors.


Yeah, for the most part, I can control the puddle quite well and my
welds are tidy enough. It's Gas, I'm talking steel tubing mostly and
it's in clusters, mostly in the "armpit" where there's an acute angle
between the tubes. I've been practicing in anticipation of finish
welding my already tacked fuselage.
If the undercutting is a problem, I think it must be in the way I'm
viewing the puddle. that is to say I'm consciously getting just a bit
too much penetration in those ares where the bead is more concave. I'm
afraid if I don't do this I'll end up with a cold weld.I'm feeding rod
in at a good rate, I think, and I also think I have the tip size and
pressures about right (it's a little difficult to get the bead started
in the tighter angles) and the weld runs fairly quicly once I'm out of
the tight area. The bead is fine once I'm running up the outside of the
longeron.. I've tried varying the angle of the tip in relation to the
work, everything from near vertical to angled well towards the progress
of the weld, but this only seems to give fine control. Less heat than
I'm using makes for a very globby, cold start. Having said all that, I
picked up my torch for the first time in a year and a half last month
and have made huge progress in welding in that space of time, so maybe
I'll get a handle on this through practice. OTOH, i don't want to
continue practicing a mistake!