DIY tube-bending tool

My plans for the milling machine oiling system call for some small-diameter bent brass tubing. I looked into the various tools designed for this, but the high end is too expensive and the low end looks pretty cheesy. I also wanted a small bend radius, which is hard to come by in off the shelf tools. It seemed easy enough to design a simple bending tool, and besides there’s nothing I like better than making stuff that makes other stuff.

My tubing has a 3/16″ OD and I was aiming for a 3/8″ bend radius (to the centerline of the tubing). I only anticipate needing 90 degree bends, but it didn’t seem any harder to allow for 180 degree bends. With these parameters I modeled up a simple design in CAD and ordered a few pieces of brass and steel from onlinemetals.

The first step was to grind a lathe tool blank to a 3/16″ diameter half-round shape. With this I turned some 3/4″ brass round rod into a set of rollers that closely fit the 3/16″ tubing.

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I then milled the end of a 4″ length of 9/16″ square brass bar to accept the smaller roller, and drilled it for a tight fit to a 1/4″ dowel pin (1″ long).

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I then drilled two 12″ lengths of 1/8″ x 3/4″ mild steel to accept the two rollers and welded two more shorter lengths of steel to create a rectangular tube handle. Done and done!

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The square brass bar is clamped into the vise, and the tube to be bent is gently clamped to the brass bar with a rubber-jawed clamp. The first test worked perfectly!

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The bends aren’t perfect– there’s a small amount of collapsing, probably from the small bend radius and the imperfect roller profiles. But I sawed through one of the bends at the thinnest part to see how much collapsing there was, and I think it’s acceptable for my needs.

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Here is the collapsed section (top) next to the normal tube section for comparison. Not bad!

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Next step: experiments in brass soldering.

15 Responses to “DIY tube-bending tool”

  1. Rick Horan writes:

    You do great work Joel. Thanks for connecting. Hope all is well with you, Jen and kid(s)?

    Rick

  2. jimbo writes:

    I think if you fill the tube with water and freeze it before bending you should be able to prevent tube collapse. Pretty sure that’s what they did on one of the “How It’s Made” episodes, either trombones or trumpets. It was one of those thin walled brass instruments.

  3. Jeremiah Baker writes:

    Thank you for posting your work on the G0704 mill CNCing. I have had your site bookmarked for over a year now and look forward to the new updates. ~ Cheers!

  4. Slowrob writes:

    Nice build for a pretty standard small ID tubing bender. The trick to reduce collapse is to make the rollers a tighter fit to the tube: should be a slight interference fit. If you want to get really silly, you could make the movable roller as a female profile to the fixed roller to enshroud the tubing.

    Nice Work!

  5. bread writes:

    For a more easy solution:

    use a threaded rod, nuts and washers like this:

    –o|=|o–

    - = rod
    o = nut
    | = washer
    = = small washers or a tube or a nut that is rasped round

    sure, this version is improvised, but if you only have to bent 1 or 2 tubes, it works great.

  6. Marc writes:

    Brass soldering can be difficult because the addition of solder can drastically reduce the melting temp where your joints are. Silver solder with it’s copper, tin and zinc added to your coper and zinc (brass) makes a very low temp alloy. It become easy to melt it all down.

    If you can braise you can silver solder. Joints have to be fit nearly perfect for the solder to flow. Don’t expect to fill gaps. For a cleaner total project flux the entire piece, it prevents fire scale. You can make flux from fine borax and water but make your self some Prips Flux http://www.debjemmott.com/Home_files/Prips_Flux%20.pdf or just buy something from your local silversmith supply or online like this place http://www.silversupplies.com/catalog/metals/silver_solder/index.shtml

  7. hardcorefs writes:

    for god sake use a circular cutter on the brass tube… not a damned hack saw…..

  8. Rick writes:

    Awesome post! You can keep the brass from collapsing by either filling with sand prior to the bend… Or by filling them with soapy water and then freezing the tubes before you bend them! (Then let the tubes thaw out!)This is what trumpet makers do!

    Hope this helps!

  9. Uncle Bob writes:

    Try filling the tubing with common sand before bending.

    Once the tube is bent, the sand will be easy to remove.

  10. joel writes:

    True, it’s a little ragged (I used a band saw). But a tubing cutter might have squished the profile, and wouldn’t have worked at all for cutting through the elbow.

  11. AbdulHamid Malik writes:

    Quote: “jimbo writes: I think if you fill the tube with water and freeze it before bending you should be able to prevent tube collapse.”
    I think ice will not work better as being solid.
    Why not fill with sand / silica as it has a good fflexibility and is an old practice in bendig pipes at small levels.
    Regards

  12. Isotope writes:

    I feel like craftsmen used to make more tools than they’d buy, maybe just because it was harder to find them or because of the expense. In any case I’ve seen lots of examples of custom jigs and special purpose tools that obviously were built with pride to last a lifetime – even if used just once! It’s nice to still see examples of this. Good job on the bender.

  13. joel writes:

    Thanks! I know there are good arguments for buying off-the-shelf tools like this, and I can’t claim that my homemade bender is a lot cheaper than a decent store-bought one once you factor in my time. But I learned a little, and got to get my hands oily on the lathe and make some sparks with the welder. Definitely a Saturday afternoon well spent!

  14. donjuan writes:

    I asked my uncle what he used to bend pipe(brake line pipes)hes a mechanic,he laughed and led me to the side of the shop and proceeded to bend the pipe with his fingers he said the trick is to make minute amount of bends at a time, just a little at a time he worked the metal tubes like a sculpture.Hes been a mechanic for 40 years.

  15. Toby writes:

    That’s cool! Just a heads up, I once saw a Youtube video about a brass musical instrument factory. I remember them filling up the brass tubes with water and putting them in a freezer for a few hours before bending them into trumpets. When filled with ice, they would bend very thin brass tubes with zero collapse!