On Mar 5, 9:01 am, "J.Kahn" wrote:
I need to make bends of about 30 degrees in a 3/4 x .049 longeron tube,
with a tight bend radius, no more than 3 inches. Can I do the bend hot
without wrinkling the tube by free bending or do I need a supporting die
of some kind? Anybody have any specific techniques?

John

This is easy to do with a torch. Secure the tube to your table, with
the horizontal tube tacked into place forward of the bend. Set your
torch with a neutral flame and heat to cherry red for about 2.5 inches
either side of the bend. Slowly bend to the desired dimension. If
your using a wood topped jig table, place a small piece of steel
between the tube and the table. Header wrap also works well to keep
from burning the table too much. If you're bending both the top and
bottom longeron you will have to alternately heat each tube at the
same time. If you're bending one tube alone, a conduit bender works
well. Practice with cheap conduit to get the hang of it first. Also
practice your bending with the torch on small scrap 4130 until you
feel confident with the process. If you go slowly, and don't over
heat, you will have a nice radius bend with no wrinkle.

Colin

http://www.jumprunenterprises.com