Originally Posted by Cyclaholic
Your points about bending are valid ones. I have a ram type bender, it has quite good dies but whether it will bend the material in question is a matter of experimentation. Even then I'm also concerned about the two bends being perfectly aligned on the same plane and not ending up with a pretzel!
As Amy pointed out, bending thin wall 4130 is problematic. Without a internal mandrel, wrinkling is nearly impossible to avoid. I use JD Square's very precision dies and followers, and haven't successfully bent 4130 any larger than 1.25" (thinner than .049). The smaller diameter tubes are not a problem if plenty of lube is used on the follower and it's bent in one smooth motion. And don't worry too much about bend alignment if you later decide to tackle the curves. Just run a carpenter's level across the forming die first, then make your first bend. Reinsert and position the tube for the second bend, then place the level across the previously bend at right angle to the die before you start the second bend. Piece'o cake. BTW, what wire are you burning?... ER70S6, or S2?
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http://www.kreuzotter.de/english/elenk.htm