Building A Tool To Bend Small Metal Tubes


[Joel] is setting up a really nice workshop. Included in his list of machinery are the staples of any workshop; a lathe, miter saw, containers full of organized screws, and a manual mill converted to a CNC machine. [Joel] wanted an oiling system for his mill, and like any good maker decided to fabricate his own. This required bending very small diameter brass tubes, something doable by hand (or without sand, at least). He decided to solve this problem with a DIY tube bending tool that allows him to bend tiny brass tubing without the walls collapsing.

[Joel] broke out his lathe and machined two brass rollers with a groove to hold his 3/16″ tubing. One of these brass rollers is attached to a handle, while the other is attached to a block that gets clamped into [Joel]’s bench vise. After threading some tubing through the rollers, [Joel] is able to bend it precisely with only a tiny bit of collapsing on small-radius bends.

32 thoughts on “Building A Tool To Bend Small Metal Tubes

  1. A much simpler way is to fill the tube with a frozen mixture of detergent and water prior to bending, similar to how they make bends in brass instruments. It’s pretty much the exact same material too, thin-walled, small-diameter brass tubing.

  2. raer has the right idea. Filling it with sand is the common technique for bending microwave waveguides, where you REALLY need to minimize cross-sectional changes.

    And for the diameter in question, pcf11 is right. 3/16 is common enough for a brake tubing bender.

    Don’t get me wrong, this is an awesome hack. And I love the job Joel did. But it can be done off the shelf for about $10-$20, with a lot less hassle.

  3. Unless you’re working with rediculously thick walled tubing, nylon rollers are perfectly adequate for this sort of thing. Also, 3/16 is a standard brake line size, so there’s no shortage of affordable commercially available solutions to chose from.

  4. Simple enough. The spring based ones work well too as well as filling the tube with salt.

    On the oiler side the guy really should be using Bijur metering units to send the oil to the ways. It will get even flow to all the ways. They are pretty cheap, the restrictors are cheapest from the Monarch Lathe service department and you can buy tees and manifolds off ebay all day.

  5. doesn’t bending pipe with these type of tools weaken the metal in the bends? I seem to remember reading that if you’re going to use any metal in structural applications you should use heat bending methods.

    1. It will weaken the material slightly, but I’ve never seen brass tube of this size used in a structural application. Bending metals with heat although easier, can weaken the material much more if the right heating and cooling processes aren’t used. Some alloys require multiple heating and slow cooling to restore original grain structure.

  6. I use 1/4″” / 3mm copper and brass to make flash steam boilers for toy boats. I have always found that annealing the copper does the job. Heat the pipe to dark red in a flame (a gas cooker works OK) and then quench in cold water. The tube will then bend easily around wooden dowels and blocks. It will work harden so for compound bends you might need to re-anneal. The pipe does flatten a small bit but nothing to slow the flow.

  7. I would suggest blanking 1 end with duct tape and pour water in the tube and blank again the other end. Put it in freezer
    ,when fully frozen you start bending it. Others are pouring molten lead prior for bending and later on removed the lead by heating.

  8. Thanks for your advice here! If you’ve ever had a broom handle made from light metal tubing, chances are you’ve had it bend. That’s why I looked into this, when you try to straighten out the broom handle, it is structurally damaged and cannot be repaired. I imagine the problem is similar with larger tubing as well. It’s good to see how the professionals do it.

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