how_to_build_a_tube

I would like to thank the good people at Blind Chicken Racing for supplying the basics to make this bender. I have taken their project a step further and have included a drawing for the sides, and will show you how the cross braces are installed.
    This bender may look complex, but it's not. Once I had my sides made, it went together quickly. Here you see a picture of a completed unit. This one has dies for 1" tube fitted, but it will take dies for up to 2" tube.
    After a few minor adjustments, this bender has worked very well for me. The body is made of 1/4" steel plate, except for the jack platform which is 3/8" and 1/2" steel plate. The jack is a 12 ton variety, A short jack with a screw extension on top is what you want.
    You can easily make changes to this unit, I'm showing you how I made mine, but feel free to change things if you like. Whatever works for you. If you check the Blind Chicken page, you'll see that there are several variants out there already.

So, the list of the materials you will need is:

For the sides - either 2 pieces of steel plate, 35" x24"x 1/4", or, (4 pieces of steel plate), 2 pieces at 6" x 24" x 1/4", plus 2 pieces at 4" x 29" x 1/4". You can use 3/8" steel also, if you want. 3/8" sides will give you a beefier look.

A pair of return springs - I used tension springs with an approx. 8" free length, approx 0.090" dia. wire, and 1" dia. overall. They work well.

For the jack platform and die yoke - 1 pc 1/2" or 3/8" steel, 5" to 5 1/4" square, 2 pcs 1/2" steel, 3" to 4" x 6".

For the lower roller pin - 1" x 8" steel rod, (if you use a high strength heat treated steel rod here, you won't need a support as shown below).

To fit the die platform/clevis - 6" long 1 1/2" dia x .25" wall dom tubing. Note: the picture below shows a piece of dom approx 3" long. I changed this length to extend the full width of the inside of the bender - 6" long. This is not carved in stone. Use whatever works best for you. Get your dies first.

To center the roller - 2 pieces of pipe or tubing that will sleeve over the lower pin, each approx 2" long.

For the lower roller pin support - 1 pc of steel angle, 1/8" x 2" x 2" x 6" long.
(this part is not visible in the above picture, and is not req'd if you can find a high strength, heat treated steel pin/shaft).

For the upper anchor pin - 1" x 8" steel rod (the stronger this part is the better). Use a high strength steel here, or maybe stainless, if its available. In mine, I used a mild steel pin that bent, then I went to a non heat treated pc of tool steel, which also bent. I then ended using a piece of high strength steel rod, which I suspect may have been heat treated. This does the job.

To sleeve over the upper anchor pin - a pc of 1" pipe, approx 1/8" wall, 6" long.

If you're looking for a good place to buy your material, I would recommend Online Metals. They have no minimum order size, and will cut you even 2" of tube, if you want it. As their name suggests, they sell most of their stuff online.

The Bend Die, Follower Die, Roller and Pin are available from Pro Tools. The pin I'm referring to is the part that passes through the yoke and the bend die (Pro Tools also calls this part a pivot shaft). The roller is visible in the above drawing. It sleeves over the lower pin, and is what the Follower Die rests on/rolls on.

I believe these parts can be made without going to Pro Tools to buy them, if you want to. This will cut the cost of the whole unit by about $175 -200 US, depending on what it costs you to have your dies made. I have included steps below to make these parts yourself, if you would rather do that.

The die set shown in the thumbnail was sized for 1" tube. It is a 3 1/2" bend radius, 120 degree type, used to fit their model HMP200 bender. This die set will work on tube up to a 0.134" wall. Their price is (as of the time of this writing), is $155 US. You will also need a roller w/Teflon impregnated bushings, and a 1" diameter pivot shaft, that Pro Tools sells. I suggest when you call Pro Tools that you make sure you order a die set that will fit their HMP 200 unit. They have different size dies, for different tube sizes and bend radii, so it depends what you need. Click on this thumbnail for a shot of their bend die and mating pivot shaft. The die shown has a short piece of DOM (drawn over mandrel) steel tube running through it. The DOM is sized with an OD so it sleeves inside the die, and has an ID sized to allow the pivot shaft to run through it.

If you want to try making a set of bend dies, I have added these drawings that show how you would make a set of 1" bend dies, with a 3 1/2" centerline bend radius. They are made from mild steel. The way that these are constructed would require that a set of three be made at the same time.

This is what you start with. A 1 3/4" (or slightly thicker) slice of large steel bar stock (7.0" dia) would eliminate a lot of machining. I haven't shown this, but the groove that the tube sits in (the 0.5" radius) would be added to the disc at this point. I have shown the dimensions n the next drawing because it was more convenient for me to do it that way.

And this is what you need to end up with. You can see that the round piece will be cut into three 120 degree sections to produce this die. The 1.5" dia hole (at the center of the die) is added to enable the round piece to be machined for the 0.5" radius. Its size is not important. Your machinist may have a preference here. I am showing a 1.5" dia hole, just bear in mind that a different size will affect the 0.125" offset of the 3.0" block.

The two blocks are welded on after. The 3.125" block cannot have any weld bead at the area where it meets the 0.5" radius, or that weld bead will interfere with the tubing being bent.

The 3.0" block cannot have any weld bead protruding past the sides of the 1.75" main die section, or that weld bead will interfere with the clevis assembly (the legs that are holding the die in place). Any welds on the sides of this piece must be 0.125" or smaller. It is ok to have these blocks welded on two opposing sides only, but I would add weld wherever possible, just to be safe.

I have shown aluminum as the material for the follower die, but mild steel would work just as well. A steel follower may be a little too heavy for most people to handle, though. Also, I am showing a length of 18". This can be reduced maybe a few inches for a 1" x 3 1/2" bend radius die, but if you plan on using larger dies, with larger bend radii, you will need 18" of length. I don't believe any kind of hardening is required for the follower if you use aluminum.

There are two more parts that work with this bend die and they are: a hoop piece that tightens up against the tube to hold it in place, and a pin that secures the hoop to the die. These parts can be made similar to this drawing:

The pin is a commercially available 0.75" dia pin, with a ring through one end to make it easy to remove/replace.

The Roller is available from Pro Tools or you can make your own. If you want to try making one, the dimensions of this piece are shown in this drawing:

The commercial version of this part has a sprayed on metallized surface on the ID. This metallized surface apparently contains Teflon, to make the roller turn freely on the lower shaft. I'm not really sure if you need this Teflon coating, but I would grease the ID really well when assembling it, and try to get a good surface finish on the Roller ID.

The Pivot Shaft is also available from ProTools. If you would like to try making your own, it is a 1" dia high strength steel shaft, with dimensions close to this drawing:

The grooves near the ends are there to allow a place for the return springs to locate. The springs will sit within these grooves. They will need to fit approx 0.090" - 0.100" dia spring wire, or whatever size you are using in your springs. The only tricky thing about this shaft is that it must be made of very high strength steel. Ordinary cold rolled will not cut it. I need to find one of my textbooks to determine what kind of strength exactly is needed here and exactly what kind of steel alloy(s) will do the job. All I can tell you is this has to be high strength. The lower shaft can be reinforced, but this shaft and the upper one must be made from high strength steel.

This is a drawing that you would use if you wanted to have these sides lasered or plasma cut from one piece. I made mine by using two pieces for each side, and welded them together at the point where the base meets the upright section. It worked well and allowed me to use two smaller pieces of steel rather than one large one for each side. I apologize for the lack of definition. The drawing lost some of its detail during the process of converting from a cad file and shrinking down to fit this page.

If you have your material for the sides, go ahead and weld them together (if you are going the 2 pc route). Or you could have your sides lasered to the same dimensions as this drawing (if you are going to use 1 piece sides). If you are making these sides yourself, lay them out and cut the holes with a hole saw. It might be a good idea to tack weld the two sides together when drilling these holes, so that both sides come out identical. On mine, I omitted the 15" notch, and moved the row of holes 1/2" closer to the edge, instead of centered on the upper part, as you see here (the purpose of the notch is to allow clearance for the jack handle when you are pumping the jack). The slot can either be made by joining up a bunch of 1" holes, or by having someone mill the space between the two holes. Whatever works for you. I had mine milled because the slot works best if the sides are clean and straight. Also, I would add a small radius to all of those outside corners (except for the top corners) if I were having these cut.

When your dies have arrived, you can begin welding the cross braces in, and use the bend die to assemble/space out the die yoke (die clevis), and to check the size of the holes in the die yoke. I'll start with the main body of the bender first. Make sure all of your cross braces are the same width. I used 6" x 1/4" bar stock for all of my braces, so that all the cross braces were 6". The location of the top brace is obvious. It is located flush with the tops of the columns. Weld it in.

Install the lower roller (the roller that supports the follower die), then position the lower aft brace so that the follower die is sitting level when resting on the brace and the lower roller.
This drawing shows what I'm talking about:

Forward/aft location of either brace is not critical, you want the braces to support the follower die as it moves along under the bend die. Mark the location of the braces, and weld them in at this point.

The next thing you will need to do is to make an angle to fit between the sides of the bender, that will fit under the roller for the follower die. Because there is so much load on the roller, the lower pin will deflect and bend if there is no support. If you can find heat treated high strength rod to use as the lower shaft/pin, you may not need support under the roller. If you are using ordinary steel rod, then you should include this support. With the lower roller in place, it is time to weld in the support for the lower pin. This should be welded in so that there is about 1/32" of clearance between it and the roller shaft/pin. The roller support is shown as the notched angle in the drawing below.

The die platform/clevis supports the jack, and holds the bend die. It is made like this:

The legs are spaced to fit the bend die. Allow slight clearance between the die and these legs. The legs will want to suck inward when welded, so make sure you leave a generous space (maybe 1/8 - 3/16 " extra) to allow the bend die to swing freely inside the clevis.

Weld the top of the jack to the pc of pipe that sleeves over the top pin/shaft when you have it all together, and you're done.

Several additional comments - Any part that sleeves inside of something else must be well greased. Although the dies and tube being bent must be clean for best results, make sure to grease everything else on the bender well.

Also, you will see that there are no tolerances on the dimensioned parts. You will have to allow for clearance on all mating parts. Try to achieve 0.005" - 0.010" clearance on any parts that fit together. If you try to make things fit as is, many of the mating parts will be size on size. Applying tolerances/building in clearances is easiest done when you see what you have to work with, so I purposely did not include these here. The dies are the most important part of the bender, so get them first, see what sizes you will be working with, and go from there.

When I tried my bender out, I found that the jack lever that came with the jack was too short. It wouldn't work until I got a longer lever. I believe that was because I was bending 0.120" wall tubing. Thinner tubing was no problem at all, and 0.120" wall is no problem now, as long as I use a slightly longer lever than the 6" lever that came with my jack. Keep this in mind when you are doing your first bends. Also, make sure that the fronts of the follower die and bend die are lined up at the start of any bend. I believe Pro Tools includes a how-to/additional info on this topic when they send their dies.