It has come to my attention that this article is actually copied from another site.  
Vancruisers.ca is all about sharing, but it sure isn't about taking credit for other people's work!

The original author is Hal Eckhart and you can find his original posting here:

http://metalgeek.com/archives/2005/05/01/000047.php

How to Bend Tubing with homemade jigs & tools

You do not need expensive machinery or heat to bend metal! Basic bending can be done with nothing more than ordinary shop tools, a bit of elbow grease, and some ingenuity.
If you're capable of lifting 100 pounds, you shouldn't have much trouble bending tubing up to about 1-1/2" by yourself. For 2", a friend is usually necessary

What sort of equipment you'll need for bending depends on the size of the tubing you want to bend. For anything 1" and up, you'll definitely want a sturdy, well braced table bolted to the floor. You can get by for a while with a plywood top, but it will eventually get destroyed. My table has a steel top, which allows for permanent holes for jigs and stops that won't tear out. This will work well for any bending up to about 2", which is big enough for bike building.

I've mostly always used 1/2" steel pins and bolts to locate the jigs. 5/8" would be better for heavy bending, but it isn't usually necessary. Bent pins are easy to fix or replace. A few large C-clamps will help keep the jig from slipping and tearing out the holes.

Spend some time thinking about where you're going to bolt down the table. Ideally, you'll want at least a 20' radius (from the jig) of clear space on two sides of the table, and a good 10' on the outfeed side. The best way I've found to anchor the table is 1/2" threaded rod and anchoring cement. Normal anchors, even big ones, always seem to fail after a while.

You'll also need a heavy duty stop to hold the tubing against the jig and a bunch of holes in your table for bolting it down. The stop and the jig must both be extremely square to the table or the tubing will twist. My favorite stop is made from a very heavy piece of 1-1/2" tubing with a bit of pipe welded on the end. The holes are offset so that I can swivel it to get a tighter fit against the tube.

One other tool that's invaluable is a sturdy router with a large trammel. Routed jigs will bend smoother and with less kinking or twisting than a jig cut with a jigsaw. If you can't get your hands on a router, just make sure that the cut is as smooth and square as you can make it.

Your trammel can be anything you want, but basically what you need is to attach a stiff bar with holes in it to your router. It can even be as simple as a strip of plywood. Most routers have plastic plates on the bottom that can be removed. Just use those screw holes to mount the trammel.

The jig material that I use the most is 3/4" medium density fiberboard, or MDF. 1" or 1-1/4" is even better. 3/4" plywood will suffice, but you might have some trouble with kinking, as it's not quite as consistent as MDF.

3/4" MDF will make a perfect jig for 1" square tubing. For 1-1/4" or 1-1/2" square, you'll want to prop up the jig with some shims so that the jig is more or less centered on the tubing. With round tubing, centering the jig is even more important. If the tube is too heavy, or the jig too soft, round tube may destroy your jig. One way around this is to bend a thin strip of steel to protect the edge of the jig.

For bending big tubing or pipe (like 2" tube or 1-1/2" pipe), you'll want to use a steel jig. The easiest way to do this is to bend two pieces of 1" tubing with a wooden jig and then weld and brace them together. This is actually better than a bent 1 x 2 because it's more consistent and the seam between the two pieces of 1 x 1 is the contact point where the 2" round hits the jig. And since the jig is 2" thick, it's the perfect size for a different sort of end stop. Just take some 1/4" x 1" strap, make a U around a piece of 2" round, and weld it to one end of the jig.

Bending Data
Keep in mind metal always springs back from the jig. Here are a few charts that show results I've gotten

1/2" - 20 ga. round tube
desired outside radius jig radius
32.5" 25.5"
30" 24"
27" 22"
21.75" 18"
21.5" 17"
12" 10"

1-1/4" - 14ga. round tube
desired outside radius jig radius
33' 12'-6"
20' 10'
16'-6" 9'
15' 8'-6"
14' 8'
13'-6" 8'
12'-6" 7'-6"
12' 7'-6"
11' 7'
10' 6'-6"
9' 6'
8' 5'-6"
7' 5'
6' 54"
5' 52"
63" 50"
54" 44"
47" 38-1/2"
44" 36"
42" 35"
37-1/2" 32"
33-1/2" 28"
30" 26"
25" 21"

1-1/2 - 14ga. round tube
desired outside radius jig radius
204" 96"
108" 68"
132" 75"
67" 48"
48" 36"

2" - 12 ga. round tube
desired outside radius jig radius
173" 108"
115" 96"
96" 75"
84" 68"
75" 50"
70" 50"
54" 46"
36.5" 29"
31.5" 25"

for small diameter bends
The easiest is to bend several times using successively smaller jigs

Tips

Bend with the seam toward the jig the weld seam is a little harder than the rest of the tube, so there will be less chance of twisting or kinking if it's on the inside of the bend. And it's usually less visible there
It's always better to slightly overbend than underbend.
Cheater bars can help you make difficult bends, levrage makes all the difference.