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COLD Pre-Bending the ends of rolled circles and hoops -- Ideas?


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No doubt everyone on this forum is VERY familiar with the dreded flat spot created in large cold formed steel circles (and scrolls, too). On a short run basis, this is no big deal, since you can hammer a nice short curve in the ends of the flatbar or roundbar workpiece. But what if you are making a ZILLION (well, 90 anyway) CIRCLES??

I find myself needing to make over ninety 15-inch circles from 1-1/2" x 1/4" steel flatbar, and that is a good thing, but I would like to save time on the ends of my 47 inch workpieces if possible.

Has anyone here come up with a quick and consistent way of prebending the ends of what will become a hoop, that they would like to share?

I've tried pressing into a small curved space and that does not seem to be the ticket to success. I would be great to have a swage block with a large radius, using a quick hammer blow, but that isn't available. 

Thanks for any solutions or hints to getting that curve onto the ends of the flatbar.

PLEASE NOTE: Often times the flat parts are simply made to overlap, and then the excess is trimmed away, BUT my workpiece is just under 4 feet in length and that allows 5 circles to be taken from a standard 20-foot "stick" of flatbar. Thus, using the trim technique would lead to a lot of wasted raw materials.

Thanks for any input!

FlatsOnHoop1.jpg

endbend1.jpg

endbend2.jpg

endbend3.jpg

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16 minutes ago, Phillip-SC said:

would be great to have a swage block with a large radius

You bought the whole anvil, not just the face. Turn it on its side and use the curve between the feet, or under the horn or heel.

Find something with a 15 inch diameter, clamp one end, and walk the 20 feet around the form.  Then cut the rings where they overlap.

The roller should let you do this.  Roll the entire 20 feet into rings at one time.

 

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On 2/22/2023 at 1:54 PM, gewoon ik said:

With a good roller you can get hoops that are nice and round. You don't have to stop at the seam when they are almost there. You can continue and make those parts round as well

Are you saying to go ahead and weld the hoop together with the flats, then put it back onto the roller? I will give it go, but have doubts about my skills.

On 2/22/2023 at 1:56 PM, Glenn said:

You bought the whole anvil, not just the face. Turn it on its side and use the curve between the feet, or under the horn or heel...

That is a stroke of genius for sure -- Thanks!

Those radii seem a bit small on my anvil though, like maybe for 8 inches diameter at most. It's just around 120 pounds (no clue of the actual brand (anybody?) or weight).

AnvilSide2.jpg

AnvilSide1.jpg

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Phillip, if it were me, if you are getting, say 2" of flats at the end when you are rolling, I'd just start with stock 4" longer and cut off the straight portions before welding the hoop closed.  It is an extra step and slightly wateful of material but if that is what your machine gives you that is what you have to work with.

"By hammer and hand all arts do stand."

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On 2/22/2023 at 5:20 PM, George N. M. said:

Phillip, if it were me, if you are getting, say 2" of flats at the end when you are rolling, I'd just start with stock 4" longer and cut off the straight portions ...

Thanks, George. As noted above, I really need to economise on the material by getting five circles from each 20-foot length of flatbar; I cannot afford to cut off any excess, since each circle starts with a 47-1/4 inch length. May as well say 4 feet. Input definitely appreciated though.

On 2/24/2023 at 1:45 PM, Scott NC said:

  Notice the location of the rolls.  

Thank you, Scott. My rollers are not configured like sliprolls are. That is, only ONE of the 3 rolls can be moved. Thus, there is simply no way to accomplish a smooth bend if the entire length of the workpiece (and no excess in length) is to be formed. In fact, the best this machine can do yields a 3-inch flat (see photos). Still working on it.

bend3.jpg

bend2.jpg

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Since your material tolerances are so close, getting 5 pieces 4' long out of every 20' stick, I would do it by welding the 2 flat ends together and then rounding the flat portion by either heating that area and forging it to the desired curve by hand or running it through the rollers again, preferably hot.  I think that is how wagon tires were done. That's the best I can suggest.

GNM

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The challenge is to solve the problem of the flat section at the beginning and end of a circle.

You should be able to bend 1-1/2" x 1/4" steel flat bar by hand, cold, against a die that you can make from metal or wood.  You do not have to make a full circle die, as a half or quarter or partial circle die will work.  Couple of bending wrenches and you should be good to go.  First circle would have a flat spot where you started, the rest would look like a coil (think coil auto spring).  Roll as much as you can handle, then cut the flat bar where it overlaps to give a smooth circle.

That leaves one 4 foot coil of stock at the beginning and one 4 foot coil of stock at the end of the bar with a flat section on the circle.  Weld the two flat sections together and bend the two joined pieces of flat bar against your die to form a round circle.   Once the straight sections are now round, cut them apart and weld them into two individual rings. 

 

 

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Thank you both, GeorgeN.M. and Glenn, those are both very good ideas, as my main target is consistency (reproduciable quality) first and time savings second. Obviously, material savings is important, too. I do pefer to work COLD in this project, so if Glenn's idea is used, I need to figure out the proper smaller radius for the tool if I go that route, due to the spring-back in bending that we are all familiar with. It is a 7-1/2 radius (15-inch diameter of course), so I'll see what happens with 6-inch radius tool to begin. Thanks!

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Like many things, you just have to eat the cost of the first stick of metal or stock.  Buy an extra stick or two to begin with in order to save a trip back to the steel yard later.  You can always use any left over stock later or on other projects.

Bending Cold:

Take your best guess at the size die you are going to use as a template.  Clear the table and set up the bending jig. The easy way is to use a dog to grab or hold the beginning of the circle. Slide the stock between the dog and the die and start bending.  The die can easily be made from say 2x? lumber.  Draw the diameter circle you want to test and cut it the die out with a jig saw.  Depending on your trial results, you can always cut it smaller if needed, or add a thin strip of wood if you need it larger.  Make things easy, use a half circle die so you only have one or two or repositions to get a full circle. 

Measure the diameter of the resulting circle, inside diameter, outside diameter, or what ever is important to your project.  Adjust your die as needed to get the diameter you want.

Now that you have the jig working, feed the stock in from the bottom so the coil rises up and out of the way as things progress.  If you can, coil the entire length of stock, or 5 circles on a new piece of material.  Measure the length of the curved stock to be sure it is exactly the circumference you need for the circle you want.  Cut the circles (stock) and put 3 good circles off to the side, ready for welding.  Put an X on the flat spots, and put the two circles with flat ends in another pile.

This is where you stop and weld up the 3 good circles to be sure that the system works to your numbers and your satisfaction.  A lay out table with say 5 dogs that you can put the circle inside the dogs, that are positioned to that the two ends come together for welding.  Any gap can be corrected by repositioning the dogs, or by inserting a wedge between the circle and a dog.  Make the weld and inspect the circle to be sure it fits your project.

Take the two flat sided circles, measure the length of the curved stock to be sure it is exactly the circumference you need for the circle you want, and weld the flat ends together.  Bend the flat sides into a curve that matches you ring.  Cut them apart and take the ring to the welding table for assembly. Make the weld and inspect the circles to be sure it fits your project.

Sit down with the 5 rings, a tape measure, and a cold drink.  Stack the 5 rings one on top of the other and see if there is any difference. This is where the 2 rings with the X can be identified, if needed.

Review the entire process to see where or if you can make improvements or changes to the system.  If you are happy with the system, make one more test run of 5 rings, sit down with another cold drink, and make another inspection, before you start final production.

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Good Morning Philip,

You can start at one end, when the end comes around, pull it slightly away from the machine. This will cause a corkscrew effect and you will only have a flat piece on each end of the 20 foot stick. Like the video above, you can form the end by hand or by making a rolling machine that will do what you wish. You could pre-form the ends with a Die that you can use in a Press. If you don't have a press, you should start making one.

Neil

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I use bending forks and a scrolling wrench, a post vice, a drawing on my table and a couple of stands. Don't create a flatspot, you just have to fix it. If you use a roller, then do the ends first with bending forks and a scrolling wrench. The tools are sized for specific size material.

image.jpeg

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All the great input and ideas are appreciated, but in the interests of time (or more precisely, getting my procrastinating hind parts started on this big project) a simple curved cradle for the hardy hole will be employed for now.

I'll just hammer both ends of the flatbar into a nice 6-inch curve - assuming a little spring back - and see what happens. Not giving up the quest for something much more consistent though.

Hardy cradle1.jpg

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SOLVED ... for now. Thank you to all who responded!

I just went ahead and made a rough but durable tool from scrap 1 inch thick steel to fit either a heavy vise or hardy hole.  The radius varies from about 5-1/2 to 8 inches, and I treaded a hole for a removable bolt/stop at the "sweet spot" for this particular project. Seems to do a good job for now.

 

Benttool2.jpg

Benttool3.jpg

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  I think his bottom rolls are not adjustable.  I was looking at your hardy jig and wondering if you could not just make something similar heavey duty and curved to the radius you need to fit in your roller without the stem and bolt to get your radius started?  Late to the party idea.

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That is correct, they are not adjustable. However, in my next (?) similar project, I will definitely use your idea; the two bottom rolls are the drive rolls on this roller, driven by a hand crank and heavy sprocket chain on the other side of the machine. I can probably add the right size ring over each roller and use a keyway or countersunk bolt in each to maintain the transfer of crank power?

Great idea - Thanks

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Phillip, I think that this is what you are suggesting, increase the diameter of the bottom rollers to reduce the "dead" space between the bottom rollers and the top roller.  Correct?  You could make different radii curves with varying size rollers assuming that you could afix them to the axle.

Another thing that I thought of is to add  the thickness of the metal to the inside diameter when calculating how much stock you need for a particular radius.  In making the curve the metal is stretching on the outside and upsetting on the inside as you roll it. So, if you want a true 36" inside diameter made with 1/4" steel calculate the circumfrence for 36.25".  It probably makes little difference for small circles but becomes significant for larger circles and thicker stock.

"By hammer and hand all arts do stand."

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Yes. Thank you both. It is now long established (over 50 hoops so far) that my 15 inch circles, using the midline as a reference, start out as 47.25 in pieces of flatbar. I'm too far along on this project to change the rolls.

The good news is I will definitely make the changes on the roller machine next time. And - more good news - while installing some of the beginning work over in Wilmington NC (3 hours away), neighbors have requested to be "next on the list" for the same or similar design. Yay!

Thanks so much for your help.

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  I might have an even better/easier way to eliminate that flat spot on your next job with a slip in fixture for your bender, but I have to draw a sketch as I can't describe things very well, if your interested.  I can pm it to you as it might be something I might make and sell myself so I can retire.....:)

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