Rolling Thin Wall Brass Tube
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    Question Rolling Thin Wall Brass Tube

    Hey All,
    I'm not sure this thread belongs on this site, since it's not about machining, but I'll give it a shot:

    I'm rolling some 2" O.D. x 0.050" wall brass tubing for a bar footrail and I'm having lots of trouble. It's kinking, obviously.

    I'm using a JD Squared Model 32 tube and pipe bender with 2" dies that give the bend a 7.5" outside radius. My last try I sleeved the primary tube with 1.875" O.D. x 1/16" wall brass tube, capped one end, filled it with PACKED, moist sand, and capped the other end. Still, I'm getting large kinks along the inside of the roll.

    Any advice?
    Thanks,
    Mat

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    Not an expert, so I'll defer to others that answer. But two observations:
    - 7.5" outside radius seems like a pretty tight radius for 2" OD tubing. Are you sure that's even an achievable bend (and doesn't require a 90 degree ell fitting for bar-rail)?
    - Not following why you're sleeving the primary tube with another tube inside of it. But the tightly packed sand seems like an appropriate step. Can you not contain the sand within the 2" primary tube and skip the inner tube?

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    The tubing is probably in a work hardened condition. Annealing would make it more workable. As Dumpster said that small a radius may not be possible. I doubt that annealing and using a bender with a mandrel would achieve that tight a radius.

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    You could try filling the tube with low melting point metal, in theUK we call it Woods metal, I think it is based on Bismuth, it melts easily and can be run out after bending

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    Quote Originally Posted by Peter Colman View Post
    You could try filling the tube with low melting point metal, in theUK we call it Woods metal, I think it is based on Bismuth, it melts easily and can be run out after bending
    That's a cool idea. I've used that stuff a bit, but got scared when I realized it contained plenty of lead and cadmium.

    As for the others: I was worried folks might say it's too tight of a radius. Annealing had crossed my mind so I may give that a shot.

    Thanks everyone.

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    Be aware that"pipe" bender and "tube" bender dies are different. Pipe is measured as ID. Tube is measured as OD.

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    Is 0.050" wall brass tubing sufficiently strong for a footrail? Or is this the standard thickness. I would have expected pipe, as a footrail will have BUFFs (big ugly fat fellows) like me standing on it.

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    I would imagine you need a mandrel bender. The old Pines benders work well

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    I rolled 50" of 7/8" OD copper with thickness .045 using this contraption I made. I worked down to a 10" diameter using about 4 passes.
    Each run through the roller was harder to push through as the center wheel is adjusted downward. If I had to do it again I would have used
    a Map gas torch to soften the tubing on each pass. I used 1/4 circle forms with a round groove to press the copper from a slight oval to
    circular again. The message here is that slow and gradual worked for me.

    dsc_0743.jpg

    Got the idea from this. I was ready to make one like it but decided it was not worth it for just one job.

    tubebender.jpg

    Result.
    dsc_0999.jpg

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    Quote Originally Posted by Hardplates View Post
    I would imagine you need a mandrel bender. The old Pines benders work well

    I agree. I don't think there's much hope of bending 2" OD x .050" wall brass tubing without some support on the
    inside. And even then you'll most likely have to anneal the tube at the points where the bends takes place. A
    rotary draw bender is not the tool for this job...

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    Quote Originally Posted by rons View Post
    I rolled 50" of 7/8" OD copper with thickness .045 using this contraption I made. I worked down to a 10" diameter using about 4 passes.
    Each run through the roller was harder to push through. If I had to do it again I would have used a Map gas torch to soften the tubing
    on each pass.

    dsc_0743.jpg

    Got the idea from this.

    tubebender.jpg

    Result.
    Attachment 271692
    That would put you around a 5.5:1 diameter to CLR ratio. The OP is trying to achieve 3.25:1 That is a huge difference and I just don't see it happening without a mandrel

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    Quote Originally Posted by nineandtwothirds View Post
    My last try I sleeved the primary tube with 1.875" O.D. x 1/16" wall brass tube, capped one end, filled it with PACKED, moist sand, and capped the other end. Still, I'm getting large kinks along the inside of the roll.

    Any advice?
    Since you tried sand, have you thought about water inside and freezing it? Sand and water were ideas that I thought too much work for a long length.

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    Quote Originally Posted by bosleyjr View Post
    Is 0.050" wall brass tubing sufficiently strong for a footrail? Or is this the standard thickness. I would have expected pipe, as a footrail will have BUFFs (big ugly fat fellows) like me standing on it.
    The inside can always be filled with something. Concrete would probably make it too heavy.

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    Not long ago I was asked to make some sharp bends in some brass tubing for a fellow at the boat yard for some vents. I do not have any bending equipment so I took it to a muffler shop. It was kinking terribly and I gave up on that idea. I ended up kerfing the pipe and after forming the bend I silver soldered the kerfs. This was not a decorative piece and you could see the kerfs but only slightly. With that tight a bend you might have to get inventive.

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    Quote Originally Posted by Hardplates View Post
    That would put you around a 5.5:1 diameter to CLR ratio. The OP is trying to achieve 3.25:1 That is a huge difference and I just don't see it happening without a mandrel
    You missed the words, "The message here is that slow and gradual worked for me."

    Agree about using a mandrel for a single shot bend.

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    Quote Originally Posted by rons View Post
    You missed the words, "The message here is that slow and gradual worked for me."

    Agree about using a mandrel for a single shot bend.
    It doesn't matter how slow and gradual you go, I don't see a nice bend that tight being formed on thin wall tubing without a mandrel or hydroforming. I've bent boiler tubes with sand in them and caps welded on the ends, while it does make the tube maintain the same volume, it does not totally prevent it from ovaling in the bend area even on heavy wall tube.

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    Quote Originally Posted by Hardplates View Post
    It doesn't matter how slow and gradual you go, I don't see a nice bend that tight being formed on thin wall tubing without a mandrel or hydroforming. I've bent boiler tubes with sand in them and caps welded on the ends, while it does make the tube maintain the same volume, it does not totally prevent it from ovaling in the bend area even on heavy wall tube.
    Especially when amateur methods like packing with sand are used.

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    Quote Originally Posted by rons View Post
    Especially when amateur methods like packing with sand are used.
    I would hardly call using sand an amateur method. Less than ideal yes, but so is anything short of mandrel bending in the OP's situation. I was simply following the repair procedures laid by Babcock & Willcox, but then again their Nation Board R Stamp number is only in the single digits, #3 IIRC.

    If you can ever get your hands on some B&W procedures they are very interesting reading, over 100 years of trial, error and engineering. Sometimes a pain to work to as they have a procedure for everything except how to wipe your own ass while on break, but lots of good info and emergency repair techniques.

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    Just another (non-expert) suggestion. Along the lines of Crossthread's advise: Perhaps you can cope the tube at the location of the bend. Similar to multiple kerfs but really only removing a 90 degree section leaving a small tab connected on the outside of the bend. With the bend area removed, bend the tab so the coped sides meet and make a single silver-solder joint. Will result in a sharp outside corner but might look ok. Otherwise follow Crossthread's and do multiple kerfs for a smoother outside radius.

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    Quote Originally Posted by nineandtwothirds View Post
    Hey All,
    I'm not sure this thread belongs on this site, since it's not about machining, but I'll give it a shot:

    I'm rolling some 2" O.D. x 0.050" wall brass tubing for a bar footrail and I'm having lots of trouble. It's kinking, obviously.

    I'm using a JD Squared Model 32 tube and pipe bender with 2" dies that give the bend a 7.5" outside radius. My last try I sleeved the primary tube with 1.875" O.D. x 1/16" wall brass tube, capped one end, filled it with PACKED, moist sand, and capped the other end. Still, I'm getting large kinks along the inside of the roll.

    Any advice?
    Thanks,
    Mat


    I've bent tubing using the sand packing method. I was doing heavy-wall 7/8" steel tubing for a motor scooter project. The trick is that the sand must be packed very tightly. I capped one end of the tubing, filled the tube with sand and then capped the other end. The second cap had a screw built into it that, when screwed in, would put the sand under a strong pressure. The bends came out OK. I can't say that this would work with thin-wall brass, however. See the picture.

    I do know that some musical instrument makers fill their brass tubes with water and freeze them before bending.
    Attached Thumbnails Attached Thumbnails 100_3107.jpg  

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