How to Shape Pipe: Rolling vs. Bending
Kevin is bending some pipe using his hydraulic pipe bender and stops to talk about getting a pipe roller and how the two differ.
First he shows the pipe bender. It has a long metal shoe that fits the actual curve you want the pipe to have. You put the pipe onto this long shoe, then raise it hydraulically into a set of two curved rollers, or shoes. The long curved shoe needs to fit the size of the pipe snugly or the pipe will flatten and, if you bend it further, kink. But if you are creating long curves, you get wrinkles - it's hard to get a long smooth curve.
To show us, Kevin pumps up the hydraulic jack, raising the long shoe, releases it, moves the pipe forward about an inch, and repeats three times to create a curve in the metal pipe. Kevin is using a pipe bender with a 12-ton hydraulic jack; there are also larger versions, and they do a really good job - on a single bend. Then Kevin shows us that the pipe was flattening on the top where the metal was starting to stretch. On the bottom of the bend small ridges or bumps had formed where the metal was unable to shrink.
A pipe roller, on the other hand, does a much better job with long smooth curves. Pipe rollers have the same sort of shoe, or die, arrangement as the bender, but has the pair of metal rollers on the bottom. They have ball bearings inside so they roll smoothly. The top single shoe is fixed to a shaft so it turns with a wheel. It is adjusted with a wrench. As you crank the single shoe down using the wrench and turn the wheel, which feeds the pipe through, you slowly shape the metal pipe into a smooth long curve.
Kevin feeds some pipe into the machine and lowers the top roller while feeding it through with the wheel. He empasizes that this is a slow, deliberate process in which you adjust down the roller about 1/8" or 1/4" turn of the wrench each time. You don't want to force the shoe down - the wrench provides about the right amount of pressure. You don't want to force it as much as finesse it.
Kevin shows how much of a curve he got with those few passes without any bumps, because the roller is rolling out the bumps as it curves the metal pipe. The pipe itself actually gets longer as you run it through the roller, depending upon the bend you are making.
Kevin got the roller at Harbor Freight. You can get much bigger rollers, too. Some are motorized; others are hydraulic. This is one he could get quickly and can store easily, good enough for something he may use only a couple of times a year.
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