Steve Eberhart wrote: > I don't know the answers and I bet most of the posters to this thread > don't either. If it were me I would track down an engineer with > experience in this area.
Well, you know me. I have no qualms about bothering other people to find out what I want to know, so I took you up on your advice and called an engineer whose job at Benedict Miler is nothing but heat treatment of stuff like 4130 for aircraft applications. I explained exactly what we were dealing with, laser cutting normalized 4130, 1/8" thick, and ambient air cooled, with a 3/8" bolt hole holding your wings on. He said "well it really depends on your exact application and the loads involved". So I said "let's just assume that what we're after is the normalized condition after laser cutting, would it be more likely to crack at the bolt hole after having been air-cooled?". He said "well, I couldn't really say, and I'm not about to tell you, that you wouldn't get any cracks, but it would be less likely than if you plasma cut or flame cut them". He said "you probablly wouldn't have a problem, but if you want to make absolutely sure you'd want to re-normalize them". I guess it's like Dana said, it all depends on how absolutely sure you want to be that your wing attach fittings aren't going to crack, as to whether or not you spend the extra effort to normalize them after laser cutting. Like I said before, the guys that manufactured TET's WAFs (and other certified aircraft fittings) said we should do it, and we did. But you can do whatever you're comfortable with, and will "probably" get away with it... Mark Langford, Huntsville, AL mailto:langf...@hiwaay.net see KR2S project N56ML at http://home.hiwaay.net/~langford
