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Picture of Easy Fork Blade Benders
Here's a simple design for a fork blade bender. This is used to bend or rake the legs for bicycle forks. It could also be used to put gradual bends in metal tubing for other uses.

It can be made with not much more than than an Oxy-acetylene torch, hacksaw, and drill press. The materials are probably all available at your local Big Box hardware store, though you should see if you could buy the angle iron as cutoff remnants from your local steel supplier, as it will be a lot cheaper.
 
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Step 1: Materials and tools

You'll need the following materials:

Angle iron, approximately 2' x 2', 2 pieces 12-18" long
Angle iron, 3/4" x 3/4", about 2'
Steel flat stock, 1" x 1/8" thick, about a foot should be plenty
2" clevis pin and a cotter pin or clip
3/8 bolt, 1 1/2" long should do, or Metric 8, or whatever you find in your junk box around this size.
A nut to match your bolt if you don't have the right tap size

And the following tools:

Drill press and drill bits
Tap to match the threads on your bolt (optional)
Hacksaw
Vise
Oxy-acetylene torch, and welding or brazing rod


Step 2: Bending the mandrel

Picture of Bending the mandrel
Open up your bench vise to that the jaws are about 3" apart. This will let you hook the angle iron under the far jaw and give you something to lever against as you bend the 3/4" angle iron.

It should be obvious, but the open part of the angle iron should point up and you will be bending downwards to make a curved piece with a v-groove. It's self-explanatory from the pictures.

Put your biggest tip on the your torch and heat up a small section of the angle iron, about as wide as your flame width. As it turns red it should start to soften and you can put a slight bend it. Then move the torch over about an inch and get that part soft and put in another slight bend. Continue working your way down the angle iron until you have a nice curved section about 12-18" long. As you advance the flame along the angle iron, you can slide the material further into the vise.

You're shooting for something between a large dinner plate and 26" rim, depending on how much bend you're trying to get. I like to make the bend a little tighter at one end than the other, to give some adjustability depending on where you end up clamping the fork leg on the mandrel. I'd suggest something around 12" radius for starting out with.

Step 3: Weld on the frame

Picture of Weld on the frame
weldview.jpg
Once you have the bend done and the piece has cooled off, cut out the section you want to use. Then cut two side pieces of the larger angle iron to match the length. Assemble it on a flat surface, clamp it together with to C-clamps, and weld or braze it at each end.

Step 4: The Clamp

Picture of The Clamp
The clamp is made from a couple of piece of the bar stock. Depending on how thick and tall your angle iron is you'll have to modify the dimensions of this part. But basically you weld the four pieces together - two legs and the top part which is two pieces doubled up. After it cools, you can round off the bottom part on a grinder and drill it for the clevis pin. Then drill and tap the top for the clamping bolt. If you don't have the right tap size, just weld or braze a nut on top instead

Step 5: Drill the frame

Picture of Drill the frame
Finally, you'll need to drill the frame for the clevis pin. I used a couple of different locations to let me adjust where over the variable radius of mandrel the bend will occurr. There's no reason you can't drill both ends of the bender to use bends at either end.

Step 6: Assemble and bend away

Picture of Assemble and bend away
Thread in your bolt, attach the clamp with the clevis pin, and you're ready to go.

Clamp the far end of the bender to your workbench. Clamp the tip of the fork blade with the bolt, and bend the leg down. You will probably need to slide a piece of larger tubing over the fork blade to get enough leverage. Some designs use two long arms mounted to the frame with a grooved nylon roller to lever down on the fork leg, which would be an easy thing to add to the frame.

If you are trying to do tight bends, large rakes, and are using thin fork legs, you might have to pack the legs with sand to keep them from kinking. The one in the photo below has a pretty tight radius, I'd recommend you try something a little flatter to start out with.

hello, have just completed your bending jig. I've added a couple of uprights and a long lever with a roller attached, it works beautifully!. It's going to save me pounds and pounds as I can now buy straight fork blades which are considerably cheaper, it also means that I can reproduce the graceful bends used by Italian framebuilders of the 1950's. Thanks again!.

Love the "heat" blue tape photo !!!…

Thanks for posting

Bikebudy2 years ago
100% Awesome ! Just what I was trying to think up. lol

Now I can build it, I will also link this tool to my Instructable as it will be so helpfull.

Great thinking......
very interesting
poother3 years ago
nice simple design,
well illustrated
love it,
gonna make one.

need to get one of those special flames and retain my finger tips for a little more time.

cheers.
¡¡¡¡¡¡¡¡¡¡¡¡¡I Have A QuestiON!!!!!!!!!!!!!!!!!!!

 I get the issue about bending the fork Blade.
But I cannot understand, How can you reduce the tube diameter at the end of the tube???????.

Thanks
drwelby (author)  voldemortkein5 years ago
Fork blades are sold already tapered. Which is a good thing.
MMMM, I got it, Its not normal cilindrical tube.


Its tappered tube, the only thing that you do it bend it.
I Say that, cuz I'm  working on a personal project "Penny farthing".

The Fork Blade of a Penny farthing doesnt have the rake like a normal bike.

But It also have tappered end at the end of the Tube.
Then, I'll buy square tube for the beginning of tube and weld a tappered tube at the end.

Thanks man!!!!
bgrasso5 years ago
i concur; this is probably one of my favorite photos ever. if michel gondry ever uses this site he'll feel one upped.
8bit6 years ago
five stars for the heat picture
dniedz6 years ago
does the bolt seat into the actual dropout, or the base of the fork leg? what would you say the total cost of this was?
drwelby (author)  dniedz6 years ago
You usually bend the legs before you put the dropouts in. So the bolt clamps the leg. I built it out of remnants that I buy by the pound, so I'm sure it was under $20 to build.
camp6ell7 years ago
could you add a picture of a fork in the bender to show how it works?
John Smith7 years ago
I'm confused...what is a fork blade bender?
"This is used to bend or rake the legs for bicycle forks."
Whoops, it was late, and I guess I just read right over that!
razordu307 years ago
This might be one of my favorite instructables pictures ever.
tiuk7 years ago
I'm commenting just to applaud your "heat" tape on the blowtorch. Awesome.
Lftndbt tiuk7 years ago
yes, I agree... very effective!!! LoL