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    Default Bending brass

    I would like some advice. I want to make a bending brake to fit a HF 20 ton shop press. What I want to do is fold brass strips for saw backs. See attached pictures for examples.

    The brass. 260 alloy. .093, 2"x 14". That is on the larger side, smaller strips would be 1.5"x 9".

    Correct me if I'm wrong but the V brake should be more acute than 90* correct? That is if I want to fold it? I would then swap out the tooling to press flat?

    Would 1/2 inch steel be a good choice for the male part for this specific task?

    Would this 20 ton HF press be good enough?

    I can weld up a brake. I have enough scraps to make most of it, except I'll need a couple of springs.



    Matt
    Attached Thumbnails Attached Thumbnails brassspine2.jpg   backs.jpg  

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    The condition of the 260 brass may be important. Annealed will bend easiest. Full hard might crack. Condition is a function of the way the sheet was rolled and the mills will sell it in different conditions. If not annealed, there will be a directional difference in plastic elongation, so it matters which way the sheet is sheared or sawed to make your strips.

    The first male Vee should have a small radius, about half the thickness of the blade stock, rather than a sharp corner. More acute than 90 degrees is good.

    Screen door springs might be about right, and should be easy to find. Some hardware stores sell assorted compression and tension springs, often made bu Associated Spring.

    I would not press flat until the blade is inside the brass.

    I do own an assortment of dovetail, mortice and other back saws.

    Larry

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    I had better results bending at 90 to rolling direction,
    Mark

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    I have a Taiwan-built 20 ton Vulcan Press that is similar in design to the H.F. Unit, but somewhat more heavy duty. I bought a press brake kit from the SWAG Co.. They build kits for such things as well as off-road accessories. It's necessary to weld the kit together, but the instructions are very good. The kit was something like $150 about 10 years ago.

    It has a 60 degree die that will do 90 degrees nicely and even a bit more if needed. later added an air-over hydraulic bottle jack unit and it really works nicely.

    I guess if you wanted more than a 90 degree bend prior to flattening, you could anneal the brass with a torch on the bend like to keep it from cracking.

    EDIT: I just noticed the radius that the OP needs. My outfit can't do anything close to that tight.


    20-ton-taiwan-press-2-.jpg
    Attached Thumbnails Attached Thumbnails press-brake-installation-001.jpg  
    Last edited by Newman109; 11-18-2020 at 11:56 PM.

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    Larry when you say half the thickness of the blade stock... are you talking about the upper piece of the brake? Bevel the 1/2 material down to a blunt point?

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    Quote Originally Posted by Matt_50 View Post
    Larry when you say half the thickness of the blade stock... are you talking about the upper piece of the brake? Bevel the 1/2 material down to a blunt point?
    Quote- "The first male Vee should have a small radius, about half the thickness of the blade stock, rather than a sharp corner. More acute than 90 degrees is good. '

    Do you know the difference between a radius and a bevel? Here is an example. If the blade stock is .050" thick, the Vee should have a .025" radius.

    Larry

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    You'll have to forgive me. I've only used a press for rough bends and pressing bearings.

    Radius where the beveled edges meet, I was still thinking very roughly here. I'm doing some reading about radius suze and lower die opening sizing in relation to the material thickness. Makes sense so far. You don't want to pierce your material or crush it. I just read about the Rule of 8 for example.

    Again I am new to brake dies but willing to learn. If it helps the blade thickness I have for small saws is .020. Using spring steel.

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    Don't laugh too hard at these, I built them in high school.



    The first brake could manage overbends in 0.047 steel with ease (thicker brass should be no problem). It was designed to get into corners and do reverse bends. The vee is made from two pieces of 3/16" welded on each side of a pieces of 1/2" x 2" bar stock. A slight bevel helps reduce marring. Since you aren't bottoming in the die it doesn't need to be vee shaped; it just needs two edges to hold the material. The punch was a chunk of 3/16 plate welded to another 1/2" bar. It was hand ground to a very acute edge with a very slight radius. This brake could do 30 degree overbends. The screws are just 1/2" all-thread, well lubricated, and I drove it with a hand ratchet. The thin tube I used around the bolts bent in the first use so I had to weld those two other bars to stiffen them.

    The second brake could manage a bit thicker steel to about a 50 degree overbend. The cam that held the fingers down was a piece of square tubing in another piece of square tubing. As the inner one rotated, it shoved the outer one inwards against the fingers. The whole finger assembly flipped 180 degrees. You would think the uneven dies were an issue but they were very easy to tighten with the brake handle lifted, and all ended up in an even line. The issue with this brake was having handles on only one side, no way to hold the fingers in place without pulling a lever, and the twisting that the thin angle iron and square tubing underwent, causing uneven bends or large radii from lifted fingers. Not an awful brake, just needed more metal. But that was expensive for me back then.

    Now, those may looks like toys, but better made version of those are awesome tools. This is what I made with them:


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    No laughing here. That bear looks awesome. Would you mind showing me a picture of the dies opened up on the first one?

    I've seen some pictures and examples of dies and punches that do not bottom out. Sides of bottom die looks squared and top die comes to a point and fits into bottom. Shape of the bent metal is from the beveled edges of the top die. And I on the right track?

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    Quote Originally Posted by Matt_50 View Post
    No laughing here. That bear looks awesome. Would you mind showing me a picture of the dies opened up on the first one?

    I've seen some pictures and examples of dies and punches that do not bottom out. Sides of bottom die looks squared and top die comes to a point and fits into bottom. Shape of the bent metal is from the beveled edges of the top die. And I on the right track?
    Here is a die set up for bend and flatten.
    Ignore the fact that the die rotates into position.
    Attached Thumbnails Attached Thumbnails roto-die-1.jpg  

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    I think you're climbing the wrong tree. A bend like that should be made on a bar folder.

    metalmagpie

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    Spoke to a friend about it, he had no folder so used a swaging roller!, seems it worked, keeping straight might be a challenge
    Mark

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    Quote Originally Posted by Matt_50 View Post
    Correct me if I'm wrong but the V brake should be more acute than 90* correct? That is if I want to fold it? I would then swap out the tooling to press flat?
    imo you're going to have to do a bit of reading on die design and how you are going to bend it. Most stuff (at least at my place) is air bent which takes the least force but get the tight radius you'll need to bottom bend or maybe even coin it - that takes a lot more force. I'd do the math first whether 20T is enough.

    Copper alloys tend to work harden, you may have to anneal it once or more to stop cracking. Just a guess, I have folded over brass that thick

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    Bar folder. I had to look it up vs a brake. I'm guessing that one that could bend this brass would be pricey. If I could use something like this to get most of the way, maybe I could finish it in a flat press?

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    Quote Originally Posted by digger doug View Post
    Here is a die set up for bend and flatten.
    Ignore the fact that the die rotates into position.
    Doug's got the right idea. If you want to use a press brake and flatten the workpiece as shown you
    need to use knife dies. They'll get your first bend way over 90 degrees and make flattening easy....

    acuteset.jpg

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    As said previously, for that much of a bend the stock will likely need to be annealed.

    Also, as a saw back has parallel sides I think you may have to do a secondary operation. In the first operation you would bend it to as tight a V as possible with an appropriately radiused punch. The secondary operation would use a flat die and a flat punch, with the final gap adjusted to the desired outside width. With proper calculation you might be able to load both punch and die sets side by side in the same press frame.

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    Annealing isn't an issue. Knife die is the same as an acute die correct? Learning terminology here.

    Having a double setup side by side or all in one would be amazing. I have a couple of friends I think I can pay to make dies on the side at work. They don't really deal in sheet metal or dies but their equipment shouldn't have on issue cutting my dies for me to weld.

    I just want to make sure I take them the correct information.

    Also I have some I beam laying around, ill have to check Ness but it is very heavy. Much thicker than the HF 20 ton press material.. If need be I can make a larger press...

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    Quote Originally Posted by Matt_50 View Post
    Annealing isn't an issue. Knife die is the same as an acute die correct? Learning terminology here.

    Having a double setup side by side or all in one would be amazing. I have a couple of friends I think I can pay to make dies on the side at work. They don't really deal in sheet metal or dies but their equipment shouldn't have on issue cutting my dies for me to weld.

    I just want to make sure I take them the correct information.

    Also I have some I beam laying around, ill have to check Ness but it is very heavy. Much thicker than the HF 20 ton press material.. If need be I can make a larger press...
    "Knife" piece is called the "Punch"
    "Die" is the lower piece (in this case)

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    Quote Originally Posted by Matt_50 View Post
    Annealing isn't an issue. Knife die is the same as an acute die correct? L..
    they're all acute. Like I said, you have figure out what type of bend is going to get you the radius (very small in this case, well beyond what you can get with an air bend) you need and design the die to suite. The image above is great, but its not one size fits all. Dies can explode if you they're not designed properly - i.e. putting too thick a material through the above die without it being designed to be strong enough. Its not like putting a man on the moon, but it should be a little more that shade tree stuff. You don't have to guess, formulas for the tonnage required are widely available

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    Dies only explode if they are hardened. I wouldn't bother with hardened dies here.

    Literally just take a chunk of steel and make a 1/2"-3/4" wide slot and break the edge. The punch should just be some flat bar machined to a point of around 30 degrees. The radius should be half of the hem gap.

    Hemming like this is commonly done and easily done. The standard trick is to use an acute punch and die to overbend to 30 degrees. Then you squish it to the desired flatness with a hemming punch and die. These are literally just two flat surfaces that come together.

    Standard V opening is 8 times the material thickness. You can go down to 4 times but run into material marring and tonnage limits. You can go to 12 or more but then the tonnage is too little to wrap the material around the punch radius, and you get a much broader bend. In cases of overbending with too wide of a die you get that broad radius to start and then a section of that radius tighten up and it looks weird.

    20 tons is more than enough. We bend 10 gauge steel to 45 degrees with less than 10 tons per foot. I don't know how hard your brass is but I expect 4-10 tons per foot with a 1/2"-3/4" V die.



    Unfortunately that one fuzzy picture was all I have of that brake.


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