1. Home
  2. ⚡ Welding Forums
  3. bend vs. miter&weld

bend vs. miter&weld

Hello,

I would like to know how to determine when to bend tubing and when to cut/miter/weld to achieve an angle in a structure.

I have a gut-feel that a slight bend is generally stronger than the same angle achieved by welding, since the metal hasn't been affected by heat. But I imagine that for a final quantifiable determination it all depends on the radius of the bend, material, wall thickness, the method for bending, available tools, the way that the finished piece is stressed in use, etc... If there is any general rule of thumb or a method for making the choice, I would very much like to find out what it is.

In case this question is too general, I have a simpler and more immediate one: I need to put a 13 degree bend on a 0.750" square aluminum tube (6061 T?) with the wall thickness of 0.120". Should I miter and weld, or should I bend it? I do not have a tubing bender (yet?), but I do have a TIG welder. For a bend this slight, do I need to borrow a bender, or should I just tweak it by hand around a lally column?

FWIW, it will be the top tube in a triangular cantilever structure, and it needs to be bent to clear another element of the structure. Therefore, the dominant stress applied to it will be elongation.

Any information that the group is willing to share on this subject would be greatly appreciated. A referral to a particular textbook or site for some reading is equally welcome.

Thanks!

-- Ilya

Reply to
iillyyaa
Loading thread data ...

Just a top-of-the-head reply here, but my practice is to use a bend if it doesn't compromise the shape too much (load is a factor also), otherwise I'll cut and weld. One challenge with bending is getting 2+ bends the same, it may take practice or finessing the bend.

Alex

Reply to
AHS

For volume production we always recommend bending parts rather than cut and weld: a bender operator can do hundreds of bends per hour, the cut and weld times are 1/10th that plus the bent parts are MUCH more uniform.

Strengthwise it's pretty much a toss up with a slight edge to the bent part. In either tension or compression the cut and weld part tends to have some portion futher out of the force axis than the bent part.

Absolute strength is computed with the same formulas as beam strength rather than Eulers formula for columns. The load is divided by the cos> Hello,

Reply to
RoyJ

I know this works for steel, so whether it will work for aluminum seems likely but I haven't tried it. TIG a bead (no filler) on the inside of the bend you want. As the metal melts and cools again it will contract and shrink that side. Controlled warpage, as you were. You will likely have to play with it, but it's worth a try, I would assume. Repeat as required.

Reply to
carl mciver

Thank you for all the replies so far. It's good to know that either option is viable, but deep inside I was hoping for someone to say: "You must absolutely bend it. You're crazy to even consider welding it." Or vice versa. No such luck huh? :-)

-- Ilya

Reply to
iillyyaa

You must absolutely bend it. You're crazy to even consider welding it. 13 degrees is just a little kink. Welding also will remove strength since the material is heat treated. Randy

-- Ilya

Reply to
R. Zimmerman

Yes, Sir! Thank you, Sir!

One additional concern though. The tube is 6061 in T6 temper, and to bend it by hand I assume I will have to heat it up to 400F and let it cool. Won't that affect the strength of the piece just as much as welding would?

Now, for the more general question: is there some online or printed resource that I could use to educate myself on making such choices on my own in the future? I am looking for a practical guide, but would be willing to read through some theory as well.

-- Ilya

R. Zimmerman wrote:

Reply to
iillyyaa

Reply to
RoyJ

Your tube will be stiff to bend without annealing but I would attempt to bend it in its normal T6 state. After all! You are only bending 13 degrees. Yes there is several sites. I don't deal with aluminum to be up on it. I confront it only a few times a year. Ernie has recommended a site. Anyone bookmarked it? Randy

One additional concern though. The tube is 6061 in T6 temper, and to bend it by hand I assume I will have to heat it up to 400F and let it cool. Won't that affect the strength of the piece just as much as welding would?

Now, for the more general question: is there some online or printed resource that I could use to educate myself on making such choices on my own in the future? I am looking for a practical guide, but would be willing to read through some theory as well.

-- Ilya

R. Zimmerman wrote:

Reply to
R. Zimmerman

Reply to
RoyJ

Good news: I found out that my friend has an honest-to-goodness tubing bender at home, and he will let me use it for this project. Now, all I need to do is buy or make an exact same bender so that we can share the dies. I'll obviously have to machine the ones that he doesn't have and make them available to him. What are friends for? :-)

Thanks, folks!

-- Ilya

Reply to
iillyyaa

Rod: Cold bending is best since the addition of heat, depending on the temperature, will change the grain structure of the metal - bad juju. Since this project IS a structure, Randy is correct, don't weld period.

To cold bend this material, you will find it will requier a large bend radius, otherwise cracking will occur. I don't have that information on hand.

Rod Ryker... The intricacies of nature is man's cannon fodder.

Reply to
Rod Ryker

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.