Bending 1/4" Square Mild Steel Bar

I've done similar projects with relative ease. Not a big deal.

If you're only making three of these half-hoops, a plywood form may be more trouble than it is worth. Can you find something like a barrel that is about the correct dia?

[Edit] Something like a big tire comes to mind...

Thanks for the reply.

Most any barrel I can think of might be a little too small. The bougainvillea has very sharp thorns that love to jump out and cut you. I am thinking of allowing about 2-3 inches on the inside of the frame as a "bougainvillea zone". I would need to have the sides far enough apart to keep skin and clothing away from the danger zone. I have not fine tuned my ideas yet but a 3' diameter arch with (framework) sides 3' apart seems like a good starting point.

Thank you,

Bruce

Yes, a barrel was an initial thought. Something larger, round and fairly solid...

Agree, three foot would probably be a minimum. Is your sidewalk only three feet wide? I am inclined to think a little wider might be better. But, this is your project, and you probably only have skinny friends.

I agree with Doorman. I'd just use a pair of vice-grips clamped onto the plywood circle to hold the bar in place. I think you can bend it by hand.

It doesn't have to be perfect, since it will be overgrown in no time and you will be the only one who knows if it's off a hair.

Thanks Doorman, Lyn & Del. I think I'll go ahead and order some steel. And I'll also try not to violate the IP of LynDoor(TM) or KrisDel(TM) when I design and build it. I know you tend to have a real fur ball over IP violations. If I have any infringing ideas I'll rip them up and throw the into the litter box.

I'm starting to wonder if 1/4" will be strong enough. You don't want it flying away (or bending) in a strong wind. Just a thought.

I was having the same thoughts. During a storm or hurricane the bougainvillea will have quite a bit of wind resistance. Also, even with a careful paint job there will be some spots thinned by rust after a year or two.

This is kind of a game of chicken. I'd love to go to 3/8" or 1/2" but I don't know how large I can go and still 1) bend by hand with about a 6' pipe and 2) bend on plywood or similar form.

I'm guessing I can probably bend 3/8". I doubt 1/2". Anyone have experience bending square rod with a 6' pipe for leverage?

3/8" should still be no trouble, 1/2" will be slower but still workable. I make dutch oven tools out of 1/2" square and I use a torch, but the bends are pretty tight... 1" to 1-1/2" R.

I am thinking in the hurricane-free mode... we don't get many here in ND. Will anything like this survive hurricane winds unless anchored in concrete?

I don't have a good torch so I will be bending cold. I suspect 3/8" is probably my limit for hand bending cold.

They will be in concrete. I suspect they will be good to 100+ MPH as long as the ground isn't totally saturated. If you get 10+ inches of rain over 24-48 hours the sand becomes very soggy and unless the concrete is deep it will not be more than just a little dead weight.

There is a "hidden feature" of hurricanes that will help keep this from failing. By the time the wind gets up to Cat 1 force the wind resistance will go down since the bougainvillea will have lost all leaves and flowers.

Bruce,

1/2" should still not be a problem.

If you can get hold of a vice mounted bending fork or a set of handheld bending forks, your mission would be a lot easier.

Plan 'B', a long pipe (3 foot, approx 2" diameter) and a vice.
Bend a short section, pull the pipe back, bend the next section and so on... this will give a nicely controlled bend.

Draw a template on the workshop\garage floor with chalk, and match each arch to the template.

Regards,
Sapper.

If it does feel a bit stiff, heat it up before giving it a thrunge.

The deadline came for free delivery so I placed an order for 3/8" square hot rolled. I'll post pictures when I am done. Thanks to all for the postings and I'll check back if anyone adds any more comments, suggestions, etc.

Bruce

I think hot rolled was a good call. I'd be concerned about bending square stock with a round pipe unless appearance is unimportant. (It would leave deformations in the square stock at every new contact point) My personal thought: Get (scrounge) an old Semi truck rim of the approximate radius, and mark the radius points with chalk or magic marker. (the rim bead area would provide the radius area to tack weld the bar to as well as the bend radius. There will be a radius at the corner of the perpendicular surface to the bead, and care will be required to keep bar stock as parallel as possible when bending, (although it should be easy to bend flat after forming) When tack welding, you could leave a few inches of the 3/8 bar below the beginning of the radius to tack weld to, then cut off the extra few inches when complete. Then you won't have to worry about grinding off the weld on the finished area of the bar stock After tack welding, with bead area facing up, (rim flat on the concrete) drive your pickup truck front tire onto the Semi rim for rigidity. Bend by hand, insuring that the bending action remains parallel to the concrete. Mark the finished radius at start and finish of radius reference makes on rim with a magic marker to cut to. (both start and finish of the radius) Move vehicle off of the rim. Grind tack weld to remove bar stock, and tack welded area of rim, remove, cut to lengths as marked: repeat. (OR) any sheet metal shop should have a roll. I'd check for price to get 3 pieces rolled at a sheet metal shop (VS. the cost of the semi truck rim) Bottom line: what is your time and effort worth??? (and do you anticipate making any more trellises????) Whatever it is, you have to make the Mrs. happy!!!

Too bad you have already committed to your design.

I have built arched trellis for climbing plants from welded mesh (concrete slab reinforcement) Easy to cut with bolt cutters, dead easy to bend. The arch is held in place with gal wire twisted onto star pickets hammered into the ground, but in your cyclonic environment a concrete foot would help keep it at home.

Wouldn't welded mesh be rather weak?

Not weak at all.

Too late any way as you've committed to your design already.

If you've put this much (collective) thought into it I'm pretty sure that you will get a nice result no matter which way you go.

Voicing a botanical opinion here now....Why did you choose bougainvillea? I would have gone with a fragrant flowering plant for an arch feature.

Happy gardening mate!

I'm with you. Bouganvillia and Wisteria are strong enough to destroy much stronger structures than this one.

I bent several decent curved sections of 3/8" round bar by laying the bar on the ground, then slowly driving my truck over one end of said bar, then bent the protruding bar up around the circumference of the tire. I then drove the truck a little further and repeated the process until I had bent my steel far enough... 1/4" square bar should be an easy bend...

Hi Bruce

Without getting to complicated, the depth of a square beam increases it's stiffness by the cube x it's width. So a 1/2" is 16 times as stiff as a 1/4" (2x2x2x2) and a 3/8" (1.5x1.5x1.5x1.5) is 5 times, which is good news for stiffness but also means it's 5 times as hard to bend. Have said that, I don't expect you to have any trouble.

It will be worth having it powder coated with a zinc rich paint or at the very least painting it with cold galv. Don't just use ordinary paint, it won't last.

Tony

Thanks for the stiffness equation. I'll start with 3/8" but I will probably be wondering if I could have made 1/2" work. This is both interesting and helpful if I am considering 1/2".

Thank you,

Bruce

Bruce,

I would order from a steel supplier #3 epoxy coated re-bars bent to your specs

Cheers

Vince

One other suggestion to make things a little easier.

I assume that you will be getting at least a 48 x 48 sheet of plywood to cut your wheel from. Use some of the scrap top and bottom of the mold to help hold the bar in line.

Will do. Thanks.

do NOT use a cheater pipe. try a conduit bender if you don't have the correct equipment. weld the bars together before bending.

I might be missing something here. What would be the problem with the cheater pipe? It also seems much easier to bend bars before welding. A few more details would be appreciated.

In bending square bar stock with a round bar, every time that you contact the square bar, it will leave deformations from the radius of the round bar. Even if you used a snug fitting square tubing as a cheater bar, it will leave a small deformation on the interior side of the radius. If appearance is not a critical issue, it's not an issue at all.

Bending thicker stuff with 6' leverage will be no problem at all IF you can hold it steady in a suitable fixture...that's the problem.
With 6' leverage you may find you are pulling your bench up off the floor, or maybe even shifting the Earth's orbit.
Del

I got in a lot of trouble the last time I shifted the earth's orbit. Will Smith and Tommy Lee Jones showed up with black suits and a funny looking flash light. I'd rather not go through that again.

When you make your former make it smaller than the required end radius as the steel will spring open.

I have done this sort of thing by screwing a piece of wood onto my bench ( say 2x4 ) and then screwing/ nailing the ply former 10mm (3/8") away from it. I placed the 10mm ss bar in the slot and just pulled it around the former. Easy.

I just read this and i realise it's not well written. The 2x4 forms a tangent to the curve of the former (at right angles to the diameter) but not touching. i.e. 10mm gap.

Jim

I think the radius should be OK, but you need to over bend the angle to account for spring back.

(also) Jim

I did think of this but I don't know how much smaller to make it. Since this is just for my yard I don't really need to conform to any specifications.

I wouldn't worry about making it smaller. You're not building something for the space shuttle. You will be able to bend in or out by hand once you have the radius bent. If all else fails, put one end on the concrete with your foot on it and push or pull on the top end. You should be able to bend it with one hand on each side.

The only problem I see is that your anchorage point will lift-up if it is not secured sufficiently to the concrete garage or basement floor or outdoor concrete patio slab (or whatever you have), especially if you use a 6-foot long cheater pipe.....

You may want to bring your bar stock to the local steel fabricator and have them bend it to your specifications. They usually have huge hydraulically operated bending machines to do this type of work, so why bust a gut or pull an arm or shoulder muscle trying to bend the steel?

Bending mild steel (like ASTM A36) may be more difficult than you can imagine with a R=1.5'.

If anything, borrow a torch from a buddy or coworker and preheat the steel......but the problem you'll encounter will be that you may burn the plywood!

Good luck on your project!

Hello Bruce,

I've seen something similar done with wood to make curved shapes. Instead of cutting an R18" form from your plywood, us it as a base and attach cleats of convenient size in a spoke array to form your radius jig. Another cleat can be used to fix one end of your bar for bending and it should be easy to add more to constrain the piece as you work it. Working on top of this type of jig will give you some support and control in 3 directions.

Remember what you'll be making initially is a big leaf spring until the material yields so if you loose your grip in the middle of the bend it will swing out into whatever is nearby.

Good luck,

Jim

Kind of like a Saturday morning cartoon. Boing, Bang, Crash, @#*! %*#@!.

Meep Meep, Swwwooooooooooooooosh.

Sounds like an ACME Bender is in the works, beware the Coyote!

http://www.ebay.com/itm/Universal-Bender-Bending-Hot-Cold-Metal-Flat-Round-Square-Angle-Steel-Bender-/180901833882?pt=LH_DefaultDomain_0&hash=item2a1e96ec9a

You could get one of these.

Then go into mass production for the neighborhood.

I have one of these benders and they work great!

I typically bend Grade 60 rebar with it...up to and including #6 bar (3/4" dia.).

You can buy 'em cheap on Ebay....check out Northern Tools Co..

I seriously doubt that you could bend an 18 in radius with that tool.

The more you practice the better you get.

Whichever way you do it, the problem will be to end up with the circular arch with the legs parallel, unless you can hold them in place at the ground level. There will be springback when you bend it over the form. Then you need two pipes and a good friend to adjust the bend. Of course, if you are a strong man, you could do it on your own.

PROJECT DONE.

Thank you to everyone that gave helpful comments.

Purchased 3 ea. 20 ft. lengths of 3/8" x 3/8" hot rolled A-36.

Cut 38" diameter half circle of 1/2" plywood as the center of my bending jig.

Made a sandwich of the half circle between two uncut pieces (only one shown below)

To prevent the jig from moving it was backed up against a mango tree. Some old cloth was used to prevent the plywood from damaging the bark. Note that any type of tree may be substituted for the mango and the orchids above the bending jig are optional.

We found the 3/8" x 3/8" A-36 to be very easy to bend with no cheater bar required. We did have trouble with it wanting to bend into a triangle rather than bending an arc around the plywood. Thus, a C-clamp was added to keep the bar against the plywood at the top of the arch.

My small back yard shop doesn't have many metal working tools. After bending two bars I used the bending jig as a table for cutting the third bar down for cross members. A C-clamp on the chop saw keeps it stationary. An old shelf bracket screwed to the plywood gave me a stop so I could easily cut all my cross members to the same length.

I have grown to hate flux core MIG welding. To use a shielding gas we had to block the wind by making a bit of a tent out of fiberglass welding blankets.

(Yes, I know I shouldn't let my nephew weld while wearing shorts and flip flops. He is twenty-something. Understand?)

Below is a picture of the finished arch. One side has bougainvillea from a vertical lattice that was starting to fail. Next weekend I'll get another bougainvillea of the same color for the left side of the arch. After a few months the grass will have filled in and the two bougainvilleas will be settled down on the arch and it should look pretty good.

COMMENTS AND LESSONS LEARNED:

1) 3/8" was no problem to bend by hand. With the info from TonyMech in postings #14 and #41 I am confident that I could have used 1/2".

2) Need to mechanically trap the bar at the top of the arch to force the bend to conform to the plywood.

3) Plywood was ok as a bending jig for 3/8" and should be strong enough for 1/2" too.

4) I need more than a half circle of plywood. As I bent the bar back in by hand to overcome the spring back I distorted the arch a little. If done over I would experimentally bend the sides too far (probably about 15 degrees extra) so the "at rest" metal off the bending jig would be correct.

5) I used the full 20 ft bar for each arch. With hard dirt this might be too much. With me pushing the bars down into soft sand it worked very well (concrete was added to the hole but the hole I dug was only about 1 ft deep.)

6) Plan ahead and buy good epoxy paint so the project isn't at risk of a short life due to low quality paint.

7) Spacing cross members at 12" seemed like a good idea and does look pretty good. As I think about weaving in the bougainvillea branches and keeping them out of the "people zone" I wish I would have spaced the cross members a little closer together.

Bruce

Great job. The bougainvillea won't care if it's not perfect. And once it gets overgrown you will never think about it again.

Nicely done.

Thank you. It was a nice little project.

Bruce

Thank you for the pictures Bruce, it looks magnificent.
The advantage of Cold Galv. as we call it in Australia, is that if it gets scratched the Zinc protects the area around the scratch. Find an old Galvanized piece of steel and cut it with a hacksaw, it won't rust.
If you do this with a painted surface the rust will creep under the paint. These frames for the roses have been there 10 years.
Tony