I remember back in the 60s it was bad to heli-arc a/c tube (4130) CM. Now Heli-arc is called TIG. In M/C (chopper) forks it would snap about a 1/4" to 1/2" from the weld. Has something changed? The long forks had an ability to flex w/o remaining bent. Was there a difference in welding process from then to now. All a/c were oxy/acetylene welded in an earlier time. Can you help me out on this? I'm confused.