Kit manufacturers cold bend their wire (at lease WE do!). The metal is bent around a post that has the same radius as the inside radius of the bend. A long lever goes over that post and has a post on it that is spaced away from the center post exactly one diameter of the wire to be bent. The lever is long enough so that a person can easily bend the wire. The wire is not clamped. As you bend, wire will be drawn from one side or the other...it's pulled around the curve.

Various guides, stops, pegs, ramps, etc. are made so that the wire can be repositioned to make a series of precise bends. The bender used also has the correct amount of movement in the pulling lever so that the wire will be at the exact bend angle when all tension is released.

A shear is used to make a clean cut in the wire.

In my experience, clamping the wire in a vise and using a hammer to help bend it will only result in broken wire. The metal must be allowed to flow as it's bent...yes, even cold metal does flow a bit when it's being stressed (bent, in this case). Hammering work-hardens the wire and makes it even more brittle.