Picture of How to bend tubing
Here, I show a quick and dirty method to bend aluminum tubing. I am documenting how I built a new bow rail for my sailboat.
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Step 1: Build the jig

Picture of Build the jig
Here, I trace the curve that I want on some scrap lumber. This scrap will be used to build the bending jig. I'm just using a couple of old 2x4's. Your wood should be somewhat thicker than the diameter of the tube you wish to bend.

Step 2: Cut the lumber

Picture of cut the lumber
Just cut out the traced jig. Use a bandsaw if you have one. I don't so, I just used a jigsaw. Cut the jig to be little smaller than the desired curve. This will allow for the spring action of the tubing.

Since I used two pieces of 2x4, I made a little gusset to hold the two together (2nd pic).

Hint: Add a little bevel inward on the bottom of the cut. This will keep the tubing from popping off of the jig when bending.

Step 3: Don't bend like this.

Picture of Don't bend like this.
If you do this, then you will almost certainly get a kink in the tubing.

Step 4: Ready to bend

Picture of Ready to bend
Here, you can see that I take a piece of scrap (from the earlier cut) and attach it to the table to complete the jig.

You will want to bend from one side only while ensuring the tubing is supported wile bending. While bending, try to keep the pressure against the jig instead of the tubing.

You may want to practice with some cheap amluminum conduit to get the hang of it. When you are ready, get the polished stuff.

Have fun.

Step 5: Mounted on the boat :-)

Picture of Mounted on the boat :-)
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That liquid foam no more gaps stuff in a spray pack works well too. It dries real quick & my aluminum pipes don't flatten/kink when I bend them. if you need to get rid of the foam when your done bending,,,then just start pouring small amounts of acetone in one end & it will eventually dissolve.

jcmaner5 years ago
if you fill the conduit with sand it will not kink
SDX42 jcmaner1 year ago
Fill it with sand and close both ends (corks do a great job here). It has always worked perfectly for me.
ehmbee jcmaner2 years ago
+1 on filling with sand-it appears in old school DIY magazines I have.
Thanks, this was very helpful!
sporgo1 year ago
Here is another tip that may help you. Pack the tube with sand before starting the bend. This provides some support from inside and helps prevent it collapsing. One other thing I dont think that trailer is large enough to carry a compac 16 !
chiefredelk2 years ago
Hey.. I LOVE your boat. I built my own sail boat. Love sailing and boat building...I also love to Cycle... I am in the process of making a Bicycle trailer and needed to bend some conduit. Can't see buying a conduit bender to use only once..Thanks for this info..Chief Redelk
Evox_Rider4 years ago
I have been looking for alternatives to buying conduit benders (they are not cheap...and I  Would doing a jig like this, but for a small 3 or 4 inch radius work for 1/2" conduit? or would it kink?
I use a spring to bent PVC Conduit. For long pipes I attach a rope on the one end and shove it down the pvc until it is in place. My spring was inexpensive. Hope this helps.
PaulE (author)  Evox_Rider4 years ago
 I think it should work ok.

Just pull very hard and go slow. You keep the conduit very tight against the jig.
 I was thinking if it does kink, to try and make a groove in the edge of the half circle part to match the conduit (thinking to maybe mount the full circle into the drill press and use it as a makeshift lathe)
Punkguyta7 years ago
I bend metal with my hands.
yeah? well I do it with my mind...
So? ... I can do it without my mind
Well, it can bend itself without me.....
its so easy, i make someone else do it for me..
you are all bending it the easy way, tubing was just flat strips of sheet metal before I started bending it into cylinders...
it was so easy...ilet u do it ...(nothing personal^, just goes wid flow)
Murdok3 years ago
If you are super concerned with getting a smooth rail, fill the rail with sand and close both ends. When you bend the tube it won't kink or deform.
rwhorton4 years ago
I have had a little experience bending tubing, as I was a band director who "dabbled" in instrument making in my early years.

I successfully bent brass tubing using molten lead (which I reheated and removed later) inside the tubing. If you are not trying a real tight curve, then this should keep kinks from forming.

Another way I have seen, but never tried, is to freeze water in the tubes, and then bend them. (Saw this on T.V.) I imagine you could place your pipe into a freezer, as long as it will fit.
dlfynrdr7 years ago
I want to make a bicycle handlebar like the one shown in this pic. Would this be a good technique to do it with? Can anyone suggest what thickness of aluminum to use? Thanks, in advance
One thing you might want to try to do is to fill it with something.  Brass instrument companies do this to prevent collapsing the tube.  They use a bees wax and tar mixture i am sure you can find a recipe online for it.  But at this point you may just want to do what another person posted which is just cut another pair of drop handle bars.
I recently watched an episode of 'Factory Made' on the Science channel. They made the bends in a brass trombone by filling the brass tube with liquid and freezing it. The ice core kept the tube from collapsing. I don't know if this would work in this case since more force would be required to make the bend than is needed for the brass tube.
Why not try something more different? like go for a shape that no one else has! and show off your coolness!
kg6gfq dlfynrdr5 years ago
Probably easier to find a set of old drop bars and apply a hacksaw.  They won't look exactly like this, but bending tube to that shape, especially with this method, seems like it could be tricky. 
It would definitely be a cost-effective way to do it, but beware about getting enough force to make the bends out by the grips. You'll have to bend with a longer tube and then cut to length for sure. Also, getting that compound bend (down and then real near to it, towards you), will require careful bracing when you build your jig. I learned that the hard way when I was bending conduit to run electricity to my swamp cooler and had to make some funky bends like that. I did the actual bending a different way, but I found I had to build a bracing jig all around the bend I had just made and then begin my next bend. It was the only way to keep the angle inact, and have a stable force to bend against. As for aluminum thickness, unless your old handlebars have collapsed in some way, use that thickness. Otherwise, I would use electrical conduit. It's cheap, handy, and relatively easy to bend. I wouldn't use it for apehangers or if I was going to put a lot of weight on my hands while I ride, but for that style, conduit should be fine.
idostuff5 years ago
Making some custom handlebars for my road bicycle... Would there be any advantage to using BOTH sand and water inside the tube?
drevt7 years ago
Great instructable! I have two questions though: I am looking at making mtb bars, out of steel preferably, and I'm wondering if a) it would be possible to bend steel using this method, and b) would it be possible to make a jig that would allow the middle section of the handlebars straight for ease when fitting it onto the stem (sort of like these )?
sti3907 years ago
What is the max size of pipe(diameter) I'm able to bend it over the jig?
Rishnai sti3907 years ago
Without heat? I guess that depends on how sturdy your jig mount is, how strong you are, and how thick the walls on your chosen tubing are. Of course, if you get some tubing home and find you can't bend it, heat with a propane torch (don't light your jig on fire) and then bend. Make sure you evenly heat everything that you want to have bent evenly, and the sky's really the limit.
PaulE (author)  sti3907 years ago
Not sure. I used 3/4 inch tubing. I would guess that as long as the jig is bigger that you would be ok. Honestly, this was a one off kind of thing (I was simply making a new bow rail). I am very surprised at the amount of discussion.
pojken8 years ago
I've seen how trumpet guys do it - they fill it with water and then freeze it. Problem is, how would you freeze it unless it's winter outside. Any how, that's another alternative if you're looking for one.
PaulE (author)  pojken8 years ago
good idea. When its not winter (or if you're in Florida like me) I bet you could dump some dry ice on it and wrap it in visqueen or a similar plastic for a few minutes.
Ribs PaulE7 years ago
Why would you want to fill it with anything at all? wouldnt that just make it harder to bend?
ELF Ribs7 years ago
Because when you bend it, the "outside" (blue line) of the curve has to be longer than the "inside" (green line). If you don't fill it, it will of natural reason deform in the profile (red circles) when you bend it... This may cause collapse, which is what I THINK is what they mean by kink. Illustration 1 is of a tube bent with something filling the inside of the tube, to force a constant volume, and thereby force the tube to stay in shape. illustration 2 is of the tube without filling. Notice the red profile cut half-way. Hope that helps :)
Ribs ELF7 years ago
Thanks a lot that makes more sence now. and it is kink i think.
Cabofixe pojken8 years ago
I just wanted to make a clarification on here. The trumpet guys don't use water because it freezes into ice and isn't bendable. Also pure water expands when it freezes and can crack or break tubing when it freezes. They use a soap/water mixture because it can still bend. And doesn't expand as much.
you can bend it just as effectively by packing the aluminum tubing with sand tightly packed into the inside of the tubing, then do the rest as the instructions say
How about just going and buying the right size conduit bender?
Conduit benders are fixed-radius, but with the wood form it can be any radius you want, even varying radius.
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