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Bending a tube without the walls collapsing or pinching.... — Parallax Forums

Bending a tube without the walls collapsing or pinching....

Beau SchwabeBeau Schwabe Posts: 6,566
edited 2012-08-05 12:08 in Robotics
Anyone have an idea how to bend a 1/4' diameter brass or copper tube into a "U' shape without collapsing the side walls and pinching the tube? .. The tube is only 6 inches long to begin with.

BTW) I have tried taping the ends and packing it with salt prior to bending it and that did not work... perhaps I need to pack the salt in it tighter.

-thanks

Comments

  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2012-08-04 16:24
    There are spring tube benders you can purchase

    Like these http://www.ridgid.com/Tools/Spring-Tube-Benders


    Home Depot sells some online.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-08-04 16:31
    An auto parts store should carry bending springs in that size. You can also use a regular extension spring from the hardware store. Just cut the loops off the ends. I've done that before with steel brake line (with one flare removed), and it works adequately. It also helps to bend it around a makeshift mandrel, rather than doing it freehand.

    OTOH, if the tubing tube is flared on both ends, you'll have to use a tubing tube bender:

    -Phil
  • jivy43jivy43 Posts: 11
    edited 2012-08-04 17:27
    Beau, Your success in bending your tube without wrinkles, or collapsing the walls depends on several factors. Wall thickness and center line radius (clr) of the bend are the major ones. The heavier the wall thickness, the smaller chance of wrinkling and collapsing. A rule of thumb for the clr of the bend is 4 times the dia (4:1) of the tube being bent. Also the use of a bending die can help. Many off the shelf tubing benders, for small dia tubes, are 3:1 so you could get a clr of .75" instead of 1". Most of these benders have bending dies to help prevent collapsing, etc.

    Jim
  • Dr_AculaDr_Acula Posts: 5,484
    edited 2012-08-04 19:26
    What Ron said post #2. I was using one just yesterday bending lots of copper pipe for a solar hot water system.
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2012-08-04 20:29
    Harbor Freight has some for $1.99 http://www.harborfreight.com/catalogsearch/result?q=65794
  • Prophead100Prophead100 Posts: 192
    edited 2012-08-04 20:50
    Beau Schwabe (Parallax) wrote: »
    Anyone have an idea how to bend a 1/4' diameter brass or copper tube into a "U' shape without collapsing the side walls and pinching the tube? .. The tube is only 6 inches long to begin with.

    BTW) I have tried taping the ends and packing it with salt prior to bending it and that did not work... perhaps I need to pack the salt in it tighter.

    -thanks

    The spring should work although I have seen ice used to help keep the diameter constant during a bend
  • bee_manbee_man Posts: 109
    edited 2012-08-04 20:52
    Instead of salt, tape the end, fill with water and dish soap, freeze, bend, thaw.
    Thats how they do musical instrument brass slides.

    Jim

    http://www.youtube.com/watch?v=kh7RrlazaRc
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-08-05 06:50
    Bee_man really came up with a rather unusual, but interesting approach. I've never tried to make my own trombone.
  • idbruceidbruce Posts: 6,197
    edited 2012-08-05 06:56
    Beau

    For brass tubing, use a brake line bender found at the auto parts store. However the key to bending brass tubing without kinking it is to anneal it first with propane or mapp gas. After you heat it up and let cool, you should be able to bend the U Shape without kinks.

    Bruce

    EDIT: This would probably also work for copper
  • idbruceidbruce Posts: 6,197
    edited 2012-08-05 07:04
    Beau

    I thought perhaps I should add more information.

    While bending, ensure that the bending shoe is always firmly against the tube to prevent slippage, and additionally, place the tubing on a flat level surface and ensure that the excess tube is always flat against the work surface and that the bender is in firm contact with the tube.
  • idbruceidbruce Posts: 6,197
    edited 2012-08-05 07:08
    You can also do incremental bends to create a larger U shape. Intead of trying to make a U in one shot and relying upon the bender radius to give you the proper size, you could make several bends at 10, 15, 20, 30 degrees, etc...
  • W9GFOW9GFO Posts: 4,010
    edited 2012-08-05 12:08
    Copper can be annealed by heating with a torch then quenched in water. Unlike ferrous metals.

    Here's a reference;

    http://steamshed.com/annealing%20process.html
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