alu flat bar, what can i manually bend ?

I've bent 6 x 50 with no issues at all. I think 8mm would be as much as I would try without resorting to additionally leverage or hydraulics. The thicker it goes the harder it is to get a neat tight bend. You might be struggling with just a workmate though.
 
pyrojames said:
I've bent 6 x 50 with no issues at all. I think 8mm would be as much as I would try without resorting to additionally leverage or hydraulics. The thicker it goes the harder it is to get a neat tight bend.
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I agree around 6 or 8mm would be my guess assuming 400x50 and with the equipment you have. A scrap piece of pipe over one end will help increase the leverage.

Keep in mind the grade of aluminium is not listed (although the title possibly suggests it is one of the 2 series) so it may have poor corrosion resistance. One of the "marine grades", for example a 6 series extrusions such as 6061 or 6063, or better still one of the 5 series such as 5083 would be a much better choice if this is for the boat.
 
About heating to soften the bar, for easier bending.

If the alloy is a solid-solution strengthened type (in marine applications, usually 5000 series), the strength won't be much changed at room temperature after heating up and cooling. You'll be pretty safe with this sort. But "aluminum alloy", if not otherwise specified, is likely to be a peak-aged type 2000.

If it is precipitation-hardened (2000 series or 7000 series, typically, and to a rather lesser extent, 6000 series) then it has had its strength and toughness properties optimised by a multi-stage heat treatment, the last stage being "ageing" at about 180-220 C to develop internal, very fine scale, hard particles.
If such alloys are heated for too long at around the aging temperature, this structure will deteriorate, and the room-temperature properties will be reduced; though actually as long as you don't overdo it, not by very much - significant overaging is quite a slow process, even at the original ageing temperature, so a brief gentle re-heat to bend will be OK. But if you get it too hot, the overaging will be more rapid; and if really too hot (about 500C) the precipitates will start to re-dissolve and it won't be the alloy it's meant to be!
Precipitation-hardened Al alloys work-harden to fracture at quite low strains at room and lowish temperatures, so bending though sharp angles may cause surface tearing. Best to make your 45 degree bend over a large, rather than a tight, radius.
And, as Noelex says, their multiphase microstructure means their corrosion resistance is not great (especially if they have been over-heated, producing coarser microstructures and odd things happening at internal grain boundaries).

(I used to be a metallurgy lecturer: the explanation of and practical demonstration of these effects was part of the first year course, and also a schools demo I did. For the demo I had 10mm diameter pure Al and 2000 series Alloy bars with various heat treatments, and bend tested them with weights, and/or by challenging members of the audience to bend them by hand. It was always quite pleasing to give some rugby-forward type chap a peak-aged bar, and one of the weaker-looking people an identical-looking unhardened bar. The tough guy would go blue in the face as bulging muscles produced no effect, while the "wimp" bent his/her bar into a U-shape, or in extreme cases, tied a knot in it.)
 
sgr143 said:
About heating to soften the bar, for easier bending.

If the alloy is a solid-solution strengthened type (in marine applications, usually 5000 series), the strength won't be much changed at room temperature after heating up and cooling. You'll be pretty safe with this sort. But "aluminum alloy", if not otherwise specified, is likely to be a peak-aged type 2000.

If it is precipitation-hardened (2000 series or 7000 series, typically, and to a rather lesser extent, 6000 series) then it has had its strength and toughness properties optimised by a multi-stage heat treatment, the last stage being "ageing" at about 180-220 C to develop internal, very fine scale, hard particles.
If such alloys are heated for too long at around the aging temperature, this structure will deteriorate, and the room-temperature properties will be reduced; though actually as long as you don't overdo it, not by very much - significant overaging is quite a slow process, even at the original ageing temperature, so a brief gentle re-heat to bend will be OK. But if you get it too hot, the overaging will be more rapid; and if really too hot (about 500C) the precipitates will start to re-dissolve and it won't be the alloy it's meant to be!
Precipitation-hardened Al alloys work-harden to fracture at quite low strains at room and lowish temperatures, so bending though sharp angles may cause surface tearing. Best to make your 45 degree bend over a large, rather than a tight, radius.
And, as Noelex says, their multiphase microstructure means their corrosion resistance is not great (especially if they have been over-heated, producing coarser microstructures and odd things happening at internal grain boundaries).

(I used to be a metallurgy lecturer: the explanation of and practical demonstration of these effects was part of the first year course, and also a schools demo I did. For the demo I had 10mm diameter pure Al and 2000 series Alloy bars with various heat treatments, and bend tested them with weights, and/or by challenging members of the audience to bend them by hand. It was always quite pleasing to give some rugby-forward type chap a peak-aged bar, and one of the weaker-looking people an identical-looking unhardened bar. The tough guy would go blue in the face as bulging muscles produced no effect, while the "wimp" bent his/her bar into a U-shape, or in extreme cases, tied a knot in it.)
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Really useful to have chapter and verse.

You can use the workmate, better with a bench vice, if you can secure the workmate it would be fine. Protect the aluminium it will scratch easily.

If the finished product is for marine use then some alloys are less resistant to the marine environment. 5083 or the 6 series are commonly used for marine application but all alloys can have improved performance if you subsequently anodise. You don't mention how big the 'thing' is, nor what it will be used for, but home anodising is quite successful (though I have never had much success in produce the fancy colours of professionals (the dyes don't merit the cost for me). Basically all you need is a container, sized for the component, a battery charger, acid, a cathode (I used lead) and some aluminium wire. There are lots of YouTube videos on home anodising.

I'll challenge you to bend a 7 series alloy, it has the strength not much different to the shank of a Rocna anchor and is used by Anchor Right for the shank of their aluminium Excel.. The 6 series bend much more easily (that's what Fortress use) and most tinnies are built from the 5 series. Note that the Guardian, which I assume is also built from the 6 series - is not anodised - and I have never heard of anyone mentioning that their Guardian anchor has started to corrode. Though the 7 series has a poor resistance to the marine environment we have had an aluminium Excel on our bow roller for a decade - the shank shows not signs of corrosion. Most climbers hardware, carabiners and abseiling links are the 7 series.

I've never tried bending aluminium, I cut and joint but mostly use it as flat plate, but have used the 7075 alloy a lot now and anodised it.

There are new high lithium alloys which are even stronger than the 7 series but are very difficult to source. The 7 series, if you need and can retain the strength, I think is the strongest commonly available. Referring to sgr143's post - the tempering details and ageing temperature is contained in the T number and you can check whether you can heat or not by simply looking up the process details.

Corrosion will be an issue, with any aluminium, if you mix it with another metal (like stainless steel) and I suspect another (or different) aluminium alloy. You need to separate the metals, Duralac or grease.

Jonathan
 
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I have bent 9.5 mm marine aluminium plate through 20 º to form a fixing bracket 70mm wide successfully using a heavy metalwork vice and timber clamped thoroughly to the leg being bent to keep the bend where it was required and provide a long lever.Without heat .I imagine the structure is severely distorted to do this but in this case the duty is simply to take the thrust from an ST2000.I practiced on a spare piece first to ensure precision.
I can't imagine that the jaws of an ordinary workmate would be man enough to do the job at this thickness .
 
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