How to Bend Steel Tubing
There are three ways to bend pipe. The first is to use a "ram bender" where pipe/tubing is bent by a jack that has an arch forcing the pipe between two wheels. The second way uses a "rotary bender" with two handles that apply leverage around a central arch. The third way uses a "roll bender" that has three motorized rollers to continuously bend pipe as it is forced through them. Does this Spark an idea?
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Instructions
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Support the inside of the pipe. In the mechanical version of a pipe bender, slide the pipe over a mandrel to help maintain the shape of the pipe as it bends. Mandrels are usually the same shape of the interior of the pipe with modifications at the tip to support the pipe as it bends. In some versions the tip is tapered into a shape like a banana or a bullet, though it can be any shape as long as it supports the pipe from the inside to prevent collapse while the pipe is bent. After sliding the pipe onto the mandrel, move the mandrel next to the bending arch before using the machine. After the pipe is bent, this mandrel must be extracted by a machine extractor that pulls the mandrel out again (since it is too hard to remove by hand).
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Make a "sand mandrel" if no mandrel is available. Put overlapping, crisscrossing layers of duct tape at one end of the pipe. The number of layers used will depend on the size of the pipe. Generously tape the end to withstand pressure, with no fewer than eight to ten layers (which cover every angle). Fill the pipe with water. Add sand slowly into the pipe to displace the water. Make sure that there are no air bubbles by tapping it with a hammer while the sand is added. Pack the sand down and add more wet sand until the pipe is filled. Dry the top of the pipe off to tape the end with a generous amount of duct tape. Take the pipe to the bender without damaging the taped ends. Be aware of the pressure built up in the pipe--it can come out with a lot of force.
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Mount the pipe to the bending machine. Open the pipe bender all the way so that the pipe can be inserted. This is done by releasing pressure or pulling apart the handles. Make sure the pipe is set into the grooves at the three contact points. One of these contact points is a central arch that the pipe will be bent over while the other two points give the arch something to push against.
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Using a ram pipe bender (method 1): The central bending arch (also called a bending die) is the part that will press up on the pipe, forcing it between the contact points to bend it. Apply the force to the pipe at the central location and then release the pipe when the bend is complete. This may be done in different ways, depending on the machine being used. If the machine looks like a car jack, it is pumped. If the machine has a big switch or lever, that is used.
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Using a rotary bender (method 2): Mount the pipe into the device. The pipe is usually gripped on each side by points near the handles and is placed in front of a bending arch. One of the handles has a flat side that runs flush with the edge. This side is to face the bench and is often screwed down. Check the screws on the side against the bench before use. Pull the upper handle toward the bench. The handles should be squeezed together like a giant pair of pliers to pull the pipe tight against the arch and create the bend. To use this device without a bench, simply hold a handle in each hand instead of screwing one onto the bench.
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Using a roll bender (method 3): Clamp on the pipe between the three wheels or rolls. One wheel should be across from the other two. As the pressure is increased, the central wheel is forced between the other two wheels, creating the bend. The amount of pressure on the pipe will change the bending radius. With the power turned on, this machine will bend pipe continuously as the wheels turn.
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Tips & Warnings
Make sure that the pipe is bent as much as you require. If the pipe springs back, it can be put into the pipe bender again to bend it just a little past the desired bend. This will require trial and error since it varies with every diameter, material and thickness of pipe.
These machines are powerful. Read and follow all the instructions that came with the device. If using sand and water or other materials to reinforce the interior of the pipe, beware of the pressures that can be created internally in the pipe and which can escape. Wear proper protective gear when bending the pipe (especially goggles and gloves), and make sure that other people are not put at risk.
