Bending aluminium bar stock

F.E.Bear

Member
I need to bend 1/4 X1 inch alum. bar stock to make a part for a steering handle on a 2 hp. outboard engine and it is subject to vibration. I think it fatigued over the past 46 years of operation. Can it be bent cold or should I heat it with propane. I did drive tractors 70+ years ago when I worked on the farm.

Fred
 
I have bent that size aluminum several times over the years. I have always bent it cold. It will bend easier that equivalent steel. Remember that should you choose to try to bend it hot, it will take a lot of heat because aluminum is an excellent conductor of heat.
 
I was told that to bend aluminum, it's best to anneal it first. The method recommended was to warm the area to be bent with a VERY rich acetylene flame, enough to leave a layer of soot on the piece.

All I can say is it worked perfectly on some 3/16ths sheet I had to bend to make a bracket. When I tried to do it cold, it cracked. After annealing as advised, it took a short radius bend very nicely.

Of course, there are lebendy-seven alloys of aluminum too, so I mighta just got lucky.
 
Back when I worked at Tracker Marine they bent all aluminum cold. Tracker Marine ois one of the biggest boat making companies in the U.S.
 
Aluminum will harden from work, or from one bend, and some harden more as a function of time, just sitting there . Anneal it first. Color the area to be worked with a Sharpie and heat just until the ink disappears. You can let it cool naturally or quench it, it makes no difference. Sometimes I anneal it more than once in a single operation, as it work hardens fast
 
There are a lot of aluminum alloys. I've found the harder ones will crack when bent. I have bent tubing and a 1/4 thick piece by heating until it smokes and quenching in cold water. It will return to it's hard state in a few days. Propane torch is hot enough.
 
(quoted from post at 20:25:24 06/13/15) I need to bend 1/4 X1 inch alum. bar stock to make a part for a steering handle on a 2 hp. outboard engine and it is subject to vibration. I think it fatigued over the past 46 years of operation. Can it be bent cold or should I heat it with propane. I did drive tractors 70+ years ago when I worked on the farm.

Fred

It depends on your material these are the most common 7075-T6 is a harder material to bend than 2024-T3 both are sold in O condition then heat treated so you would have 2024-0 and 7075-O The trick to bending a hardened aluminum is the bend radius The larger the radius the less chance of cracking. Your not going to bend 1/4 thick plate at a 90 degree angle particularly 7075 T-6 without it cracking. Id have to look at the chart.unless it in O-condition even O condition has a minimum bend radius. You can look it up on line or let me know what material you have and the angle of the bend.

Byron
 
(quoted from post at 02:39:22 06/14/15) this some old alum. stock for the DIY from the hardware store that I need to bend with no sharp radius.

How much of a bend? approximately 30 45 90 degrees may be post a picture of the part you making.
 
Have You tried finding a replacement part?
Here's a link to Doug Penn's website, he sells Used parts for
vintage and antique outboards. He is really helpful, if he doesn't have the part,
he will help you find it.

http://penn.itgo.com/

Another place to try is the free want ad's on the Antique Outboard Motor Collectors club website.

aomci.org

Good luck with Your motor.

Steve A W
Doug Penn
 
(quoted from post at 02:39:22 06/14/15) this some old alum. stock for the DIY from the hardware store that I need to bend with no sharp radius.


All alum stock has a number stamped on it. Here's a chart with some common material types and how to use it.

Example Take 5052.H32 take your thickness 1/4 .250 times 1.5 for 90 degrees = .375 or 3/8 radius Use .5 for 45 degree angle .250 X .5 = .125 or 1/8 radius

Use a piece of wood that you can grind down the edge to the specified radius to bend your part around clamp in a vise and bend. Use 1/2 of the total radius so in the first case (BELOW) you would use 1/2 of 1.75 =.875 or 7/8 Radius. ( Example for a 1/2 inch radius you would use 1/2 of 1/2 or 1/4 radius this will give you the nominal radius in the chart)

2024-T3 .250 X 7 = 1.75 or 1 3/4 inch radius @ 90 degrees
2024 T3 .250 X 5 = 1.25 or 1 1/4 inch radius @ 45 degrees

Smooth the edge of the material where it will be bent with a die grinder and 100 grit smother is better remove any sharp edges in the area of the bend to reduce the chance of cracking.

Now if you saw NOTE 2 for 2024-T3 this would be your best bet if you needed to heat it to obtain a tighter radius the quenching can be done in oil but for what your doing just use water. Water is the fasted cooling method oil would be the slowest with the exception of forced air. 2024 T3 will come back to its original hardness after time (ageing) Be aware that some materials will not return to there previous temper.

Now you can see material type, hardness & thickness is important in determining the minimum bend radius. I would comfortable using these numbers on the chart for 90 and 45 degree angles.

2024-O you could bend with a 1/4 radius but it would be to soft and I doubt you would want to go through the heat treat process after bending

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