The piece is only about 50cm wide and 40cm high and 4mm thick. It is a
bracket . It needs to be bent in a straight line, only about 4mm high. What
techniques would you recommed with tools in a typical garage?
All aluminum is not created equally. Some alloys will bend readily, others
will bend, but only across the grain. A good example is 6061-T6, which will
likely break instead of bend. Can you provide more information on yours?
It can prove challenging to make such a short legged bend in something that
rigid. I'm not convinced you'll be successful.
If it's a sharp bend of more than 45 degrees, you'll have to anneal it
otherwise it may crack. I forgot what the proper annealing temp is but
think it's about 800 degrees F. Heat gently and evenly with a propane
torch or gas range burner, then quench in water. Then it will be almost
as soft as copper. It's quite easy to get the aluminum too hot, close to
melting temp. I'll defer to those more knowledgeable to give the correct
annealing temperature and how to judge it--something about a pine stick
touched to the aluminum, leaving a char mark...
Does your garage have a vise? The jaws probably aren't suitable for
precision bending, so you'll need a couple jaw protectors. Couple pieces
of angle iron bedframe, or new 1" x 1/8 angle iron from the hardware
store, cut to the width of the vise. You might want to round the corner
of one piece of angle where the inside corner of the bend will be, with
a file (every garage has a file, right?)
It will be difficult to bend 4 mm of 4 mm thick aluminum, or any metal,
evenly. You could clamp that 4 mm section in the vise and bend down the
larger section. But your average garage-type vise will likely not hold
it evenly across the width and it may slip out of alignment. So you're
probably better off to hold it by the larger section, and tap the 4 mm
lip down evenly across with a garage-type hammer until you reach the
desired angle. It would be easier if you could make your piece oversize,
then cut it off to 4 mm afterward.
An alternative method is to lay the piece with the bend line over a
V-groove cut to the desired angle in maple or other hard wood (or
steel), and use maybe a mason's wide chisel to whack it good and hard
with a big hammer.
Either way, you should try to get the bend done with as few hammer hits
as possible since each hit will retemper the aluminum and work-harden it
to the point of being brittle and easy to crack.
Yeah, well either 6063 or 6061, but will probably use 4mm 6063. I guess an
alternative would be to use 6061 2-2.5mm. The bracket needs to be reasonably
strong. The height doesn't have to be 40cm and can be higher to accomodate
an easier bend.
Hope that helps.
Thanks, helps alot. Guess will rty to use the torch method.
> Stewart wrote:
> > The piece is only about 50cm wide and 40cm high and 4mm thick. It is a
> > bracket . It needs to be bent in a straight line, only about 4mm high. What
> > techniques would you recommed with tools in a typical garage?
> If it's a sharp bend of more than 45 degrees, you'll have to anneal it
> otherwise it may crack. I forgot what the proper annealing temp is but
> think it's about 800 degrees F. Heat gently and evenly with a propane
> torch or gas range burner, then quench in water. Then it will be almost
> as soft as copper. It's quite easy to get the aluminum too hot, close to
> melting temp. I'll defer to those more knowledgeable to give the correct
> annealing temperature and how to judge it--something about a pine stick
> touched to the aluminum, leaving a char mark...
> Does your garage have a vise? The jaws probably aren't suitable for
> precision bending, so you'll need a couple jaw protectors. Couple pieces
> of angle iron bedframe, or new 1" x 1/8 angle iron from the hardware
> store, cut to the width of the vise. You might want to round the corner
> of one piece of angle where the inside corner of the bend will be, with
> a file (every garage has a file, right?)
> It will be difficult to bend 4 mm of 4 mm thick aluminum, or any metal,
> evenly. You could clamp that 4 mm section in the vise and bend down the
> larger section. But your average garage-type vise will likely not hold
> it evenly across the width and it may slip out of alignment. So you're
> probably better off to hold it by the larger section, and tap the 4 mm
> lip down evenly across with a garage-type hammer until you reach the
> desired angle. It would be easier if you could make your piece oversize,
> then cut it off to 4 mm afterward.
> An alternative method is to lay the piece with the bend line over a
> V-groove cut to the desired angle in maple or other hard wood (or
> steel), and use maybe a mason's wide chisel to whack it good and hard
> with a big hammer.
> Either way, you should try to get the bend done with as few hammer hits
> as possible since each hit will retemper the aluminum and work-harden it
> to the point of being brittle and easy to crack.
> Ken Grunke
I agree with everyone else, that putting a 4mm leg on 4 mm thick material
will be extremely difficult. It will be hard to hold, but also, try to
visualize where the material is coming from to fill in the arc of the bend.
It has to come from the material on both sides, and the bend part will use
up a good portion of the 4mm side.
Consider slotting the plate most of the way through, then making the bend
and welding back to stiffen it in the bent position. Or, just place a 4mm
square bar in position and weld it.
[ ... ]
[ ... ]
Hmm ... I *think* that we've got a problem of mixed units. We
are accustomed to working in inches and thousandths thereof in Imperial
units, or in mm *only*. Cm are not often used in a machine shop. And
you are specifying mixed mm and cm.
So -- your workpiece (translated) should be
Now -- that "4mm high" at the end -- is that truly correct? and
do you mean by it that the inside corner must have a right angle,
instead of a radius, since the thickness is also 4mm? This is an
unusually sharp bend, if that is truly what you are requesting, and
increases the chances of the aluminum splitting.
Or is it really 40mm, or even 400mm, as suggested in this
fragment of your latest reply:
Please re-post the request entirely in mm, and double check the
dimensions -- including how sharp the bend needs to be. With an
allowed radius, the aluminum is much more likely to survive the bend,
and will be *much* stronger than a sharp bend would produce.
And if you do mean that one leg after the bend should be only
4mm beyond the bend (sort of like this):
you might be better off doing this with a longer workpiece, and then cutting
off the excess length of one leg.
As for your final line of the original request:
Whose garage is typical? In *mine* there is a DiAcro 24" finger brake,
which could (possibly) do the bend, though 4mm aluminum might be a bit
A hydraulic brake, which presses a 'V' punch into a 'V' die to
bend the work between them would be better for the task, I think. Some
people in this newsgroup have hydaulic presses in their garage. But
with 6061 or 6063 (T6 temper), this is again too sharp a bend.
A really large and heavy duty vise might allow you to clamp the
aluminum between the jaws, and use a length of 2x4 to transfer hammer
blows to the part extending. above the jaws, but it can result in an
ugly bend. And with 6061 (or probably 6063) in normal temper, you will
be very likely to crack or brake the workpiece, no matter which means
you use to attempt that sharp a bend. You want a very soft aluminum to
manage that -- perhaps even pure aluminum.
Converting your dimensions to inches (so I have a better feel of
them) suggests that you don't have that big and heavy a vise in your
garage. :-) (500mm by 400mm is 19.685", and 400mm is 15.748"
The bends across the grain survive better than those along the
grain (it likes to split along the grain), but you appear to be really
asking for something too sharp. Given your dimensions, what *I* would
be likely to do is to get some aluminum plate 8mm thick and of
sufficient size to make the whole of your workpiece, and using a milling
machine or a shaper, thin all but the sort leg of the "bend" to 4mm. I
would do this especially if it needed to be a hard aluminum alloy, which
does not bend well. And I have both milling machine and shaper in *my*
garage -- but your workpiece is too large for *my* shaper.)
Do you want to list what tools *you* have in *your* garage?
Then perhaps we can focus our answers a bit more.
It may be that the best way for *you* to do it is with a tool
which is only in the garage when *you* are there -- your wallet. Find
someone in town who does sheet metal work, and pay them to do it.
OOps, the last two words are the big ones! You have a problem!
I suppose you could put it in a big vise and wail away at it with
a hammer. A bending brake of some sort is the desired tool, and
it would have to be a big one to handle 4 mm material.
You are most likely going to have to heat it and quench in water
to anneal the heat treat, or bending will be impossible without
fracture. Even with annealing, it is going to be very difficult
to bend this without tearing at the outer edge.
Really, if it needs strength and a flange equal to the thickness, I'd
be thinking more of machining the whole part out of wrought
aluminum stock, and forget bending something of this thickness.
how do you find which way the grain runs in aluminum? Without bending
it, that is. Is there a way to tell visually?
I suspect it's only in extruded or rolled aluminum, not cast.
Well, 99% of the time there's a brushed finish which obviously will show up.
Sure it can be applied crosswise, but what are the chances of that?
Probably more likely you'll break the tap in it on the last operation or
Ya. Castings have crystals which point radially in from the sides, up to
the very center which tends to be more uniform. Certainly, a cast plate
will be better than a rolled plate if you're working it in both directions.
(Hmm.... wonder if hammered plate can be had anywhere...)
Continuous cast is a different animal...
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
It's not always obvious, especially if the piece is small enough to not have
any printing on it. My experience dictates that information on aluminum
sheets is always printed parallel to the grain, or along the long distance.
In other words, on a 4' x 8' sheet of aluminum, the grain would run parallel
to the 8' side.
If you can see signs of rolling, that's a dead giveaway, too However, I've
seen more than my share of aluminum that shows no sign of direction. In
a T6, or other hardened condition, it might be prudent to make a tight bend
on a small sample. If it's bent with the grain, it usually breaks. Against
the grain (crosswise to the grain) it will tolerate a much tighter bend
Hope this helps. Beyond what I've stated, I guess you could also acid
etch, which would likely show grain quite well.
Hmm ... now that we are sure that it is that small, and the
overall dimensions suggest that the length to be bent up was 40mm, not
the 4mm stated (you must have meant "4cm" there), that sounds a lot
closer to something which you could do, I think that my DiAcro brake
could handle a piece of 4mm thick metal that small -- though I would
have my doubts about something closer to its full 24" (609mm) capacity,
where the design specs are for 16 Gauge steel (about 1.59mm).
And with a large bench vise (with a depth of jaw from top of jaw
to the part which projects into the base of the vise of at least 40mm,
and preferably 50mm), a good heavy hammer, some angle iron, and a piece
of 2x4 to spread the hammer's force, it should be possible to do it. I
would advise rounding the edge of the angle iron with a file or a
grinder to increase the bend radius of the aluminum, and ideally using
heat to anneal it to reduce the chances of it cracking.
As suggested by others, take small samples of the material and
try bending them in both directions, to see which way the grain works.
Probably pieces perhaps 6mm or so wide by about 25mm or so long would
suffice for the test -- and a vise without the angle iron plates would
do the job. Mark the pieces with different colors of magic marker on
all sides so you will be able to identify which orientation each had.
After bending, it will become apparent which way the grain runs by how
the cracks form.