aluminum tube bending

No, it was advising him, the wrong way, sand, , God I have heard that crap from all over the place, wont do a thing
Now IF I want advise on photogaphy I will most certainly ask you, if I want advise, of CAD I will ask the boffins, I dabble in cad, but I dont try post abt it, you dabble in metal, and it is obvious you know nothing, so I must point this out, and I do not mean to offend, I hope you can see this

 

You can't use heat to help bend aluminum tubing. You use heat to help bend steel as heat causes steel to become pliable without abandoning its basic crystalline structure, thus retaining strength (inversely) proportional to its temperature.

Aluminum, OTOH, goes 'hot short' in that is transitions VERY ABRUPTLY from solid to liquid without a pliable interphase state like steel has.

The low alloy (non-hardenable) aluminum extrusions bend readily and only work harden slowly, but they are of no interest to you. The higher strength (hardenable) alloys like the 6000 series should be bent in the annealed (soft, un-hardened) state and then hardened (heat treated) as needed afterward. Whether the metal needs to be fully annealed before bending is partly a function of how much bending you need to do. As other posters have already mentioned, bending will work harden the metal. The deeper the bend, the more hardening. If you start out with hard metal (say t-6), you will not be able to bend it much before it cracks. But you just may be able to bend it some. How much? I can't say for sure, I can only guess. In production they work out exactly how much bending they can get away with and then they do that amount of working(bending) of the metal each time and it works the same way every time.

Your project is more like a one-off; you want to make it once and never again. In that context you would likely start with metal in the annealed state (T-0), do your bends then have it heat treated, if needed. For a structural part, you will really want it to be heat treated as is greatly increases the yield point and fatigue life. The bent areas will already be somewhat hardened; they may be fully hard, again, depending on the bend. That's why the first step in heat treating is always to re-anneal the whole piece to get it back to fully soft, 'T-0'. Then the whole part can be treated to the same hardness.

If your pieces are not huge, you can get them treated for reasonable cost in just about any medium to large city. I had some heat treating done on some 2024 T-0 here in Orlando a few years back, and Orlando is not really much of an industrial town.

Jimbo

 

how very strange Jimbo, I must have imagined I was bending and annealing that tube, 2 inch, thats why you use the black on it

 

This is what I was trying to say, it just didn't come out right!

Sorry to cause confusion!

 

Yeah, if you're REAL careful you might be able to anneal without ruining. But get it just 100* F too hot and it could collapse. The heat gun is definitely the way to go if you want to try annealing on your own, especially if the material is thin. Once you get to 4mm wall, I doubt a heat gun could anneal a workpiece of any significant size. It just takes too much heat. All the heat sources large enough and readily available to the DIY person (torches) get too hot thus endangering the work by overtemp. Once the piece is big enough to weigh a few pounds, then a heat gun just won't have enough thermal energy, you'll need an oven. Starting with T-O aluminum and getting it treated after bending is a good way to go. T-O bends like butter, too. Almost like soft copper.

Jimbo

 

Thanks to both of you. The view is a cross cut of the hatch, in the area of the hinge. A 3/4 tube is fixed to the deck (on a 90 degr bar) then a 1 inch tube is bent to a circle, then cut edgewise, mounted open side down...

 

Bending or Rolling or Roll Bending

glensail, LazyJack, Jimbo1490, and others on this topic,

We haven't really stated the three ways of forming a sweep in pipe or tube and it seems that has left the discussion talking apples and oranges. I'm not sure everyone was talking about he same subject in some of the exchanges?

There three general ways to form bends in pipe/tube. One is press forming benders (http://www.toolup.com/greenlee/880.html ) that have a shoe or slipper already in the shape of the inside radius of the bend and they simply press the pipe or tube against a set of pivoting posts. When the pressure is enough to deform the pipe or tube it bends and with a bit of spring back stays where it was deformed.

The second method is to roll the same extrusions with a 3Pc or pyramid rolls, also called and angle rolls, ( http://www.bii1.com/benders_ringroll_faq.htm )and that will form closer radius than the pressing only method above. This is because on each 'pass' or trip through the rolls, the deformation is subtle so the elastic limit is not reached and the material doesn't crack or snap.

Finally, the third method is the roller follower type of bending in which a formed roller 'wipes' the tube or pipe around a die similar to the first methods' shoe or slipper. ( http://www.hossfeldbender.com/ ) This method has a roller formed to the outside shape of the pipe or tube and that is pulled around the outside path of the shoe or die. This method holds the pipe still and is somewhat a combination of the first two methods.

Breakage of aluminum pipes with the first method is greatest if you don't sand the two pivots smooth and use a lubricant because the tube/pipe has to slide into the forming die or shoe. If the two pivots are a fixed distance apart in a straight line, and straight pipe is placed between them; both ends of the pipe have to come toward the center as the distance around the shoe or die is an arc- therefore longer than the straight distance of pipe between the two posts.

With a roller bend, the results can be tighter radius but there is still a limit to the pipe or tube's wall deformity. With the last method the roller forming the bend pulls the pipe around the die to create the bend and since it rolls it will not pull (too much) on the pipe so it won't tear the sidewall as much or as often as the first method.

The tightest bends in almost any circular hollow material can be achieved with a mandrel bend. This method uses one of the above methods to do the bending- but has a series of roughly round balls inside on a cable- like 'thimbles on a string' called a mandrel. These will flex with the bend but help to keep the sidewall of the tube from collapsing and wrinkling.

Most pipe (ID measured ) or tube (OD measured) aluminum tube is 6061-T6 or 6063 many times supplied as T4 or T5. The latter material is more malleable and has greater elongation than the '61 which is more 'brittle'. Almost all 50 and 60 series aluminum will work harden by bending. So if you take 6063 T4 and bend it - you end up with a section of 66061 T6 ESSENTIALLY ( not literally) with much less breakage and cracking.

H-32 and H116 material, mostly the 5086 or 5083 materials aren't heat treated they're work hardened or aged by rolls when they're 'almost cold'. This is a property that isn't being discussed but is very important to the experiences everyone here is reporting. The 60 series is heat treatable but will have the same work hardening as the 50 series and that is why the flame or heat gun annealing can help with bending.

If using 6061 tube/pipe to bend but controlling the temperature up to 350-400deg F, or so, you can 'soften' [annealing effects the residual hardness not necessarily the elongation factor] the material by extending the elongation (limits) before failure property in a limited temperature range. As mentioned above, if you're a few hundred degrees (F) high- the whole piece of metal fails and if you're too low then you just wasted the time and have some hot stock.

A good means to control heat when using a torch is to use a temperature crayon. These paper and plastic wrapped sticks are a mixture of clays and paraffins and they melt at specific temperatures. They're usually available at the welding supply store. By using a torch to burn off soot, that was deposited as a temperature indicator as it 'burns off' at 380-390deg F, you're getting the same result (!) but maybe with less control in the hands of the inexperienced?

It's easier to buy the softer '63 T4 orT5 and bend that because the stuff ages, literally, into 6061 T6 in a few years of in minutes if you bend or work strain the piece. In fact the most common mistake is to buy OLD 6063, which has hardened into 6061 !!!, and then break it thinking you're using the softer material and being confused why it broke?

The concentric diameter hatch cross section shown would be best done with a roller forming method because the concentric pipe sizes- say 3/4" and 1" don't have the same arc centers for the bends making the press forming or even roller follower type (Hossfeld bender in the US) unsuitable. I'd prefer not to take the job because of the large amount of time needed to get a four sided or oval shape form two concentric pipe sizes.

You'd need to work quite a bit to get a 2'x 3' hatch (roller formed) because the 3rd roll would need to be put down onto the pipe and lifted at the straight sections to get a rounded rectangle. If you went for the OVAL shape (?) the work is even more difficult as the separate arc radius would be a real bear to adjust.

So I'd suggest that you consider straight sections of pipe with forged butt weld fittings TIGged into the corners if you want to follow the design concept. These are concentric by size and the short radius's make the hatch opening more useful area, for a given size, while making most of the job working with straight pipe lengths.

sorry that I got a bit long winded here but there was a lot to remark about gone before.

cheers,


If you're going to go for a

 

kmorin, is it Ken?
look
i dont carry on to the length I often should, the reasons being is that you always get someone who knows nothing, writing OVER the top of you, not really reading what one says
i read your posts, you a re hands on as are some of us
i am too old to try convince people who (know best)
i have other places to direct my energys, and learning new things like CAD ,takes time
I often invite people to leave a tel number, its easier for me to talk someone through this than write them through it
best regards Stu

 

Reading Articles on the Web

Stu, it's Kevin and I hope you didn't read my post as criticism.

I realize why you make remarks that are shorter than you might and I'm aware of the many who post that may not have as much experience or just plain ill informed.

There is also another group, whom I respect and am always aware of when I post; the serious reader who is interested in learning and doesn't post. These folks are the main body, in my completely unsupported opinion, of the specialty site's readers.

I wanted to offer a summary and show that lots of what was said was just "different part of the same elephant" to use the old folk story as a comparison. Lots of times discussion move around the original topic without making some clearly defined statement about the overall circumstance -like bending pipe.

Those of us who have or do still work in the trades, know more than folks who have less experience actually doing metal work and so I feel like it might help the sincerely inquiring reader (I'm not missing the presence of someone who posts without as much factual knowledge) to have a general summary statement once in a while- and that is no comment on anything you've posted.

My remarks are intended to help the reader who finds this thread next year, with the same or similar lack of work experience that the two questioners here have/had, find a thread that helps their inquiries along. At the same time, I'd like to see if I can help clarify some of the obvious facts that you and I wouldn't need to mention if we were holding the same conversation over a pint. What happens in lots of specialty website forum discussions results from the level of knowledge gap, where the language used by the tradesman isn't even understood well by the apprentice. I hope to help those apprentice level people to move their knowledge upward but don't mean to sound like I was disagreeing or finding fault with your remarks.

I remember my younger days as an uniformed young builder craving good information and having to learn by mistakes- it was ugly and expensive and I'd like anyone who is inclined to learn the 'easy way' to skip my millions of hard-way lessons.

What CAD system/application are you working on? Marine or just drafting/general modeling?

cheers,
kmorin

 

i for one really appreciate your work, and the likes of a few others who really put into the place a great deal of effort, TSpeers, Rick W, Graig Cay, and the men from the Borban Dolphin threads, and many more with whom at this point in time, I would swap skills for math ability
I Am also aware that i am becoming irritable and short fused, this is because I have sat here for 7 years doing nothing, i thought I would enjoy retiring, but I have not
So that is why I am with the considerable help of bhnautika here, am working on a new design to market in Eu
i am using Rhino, , I find doing structure easy, i dont even have to do calcs I have it all in my head, but 3d modelling baffles me and sometimes I go 8 hrs and achieve nothing
Sometimes if you do a google search it leads to this forum, in fact I did not realise that by leaving my contact details here, they are all over the www,
You did not at all offend me, the only person to have done that was a guy called Frosty who called me a liar and a homosexual .)
keep at it
Stu