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Old 01-31-2019, 09:00 AM   #1
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bending/cutting copper tube

My forced air diesel heater came with 3/16" OD copper tube for the fuel line. I've never worked with this stuff before. It shipped in a 12" diameter roll. Can I put a smaller radius bend in the tube without having to buy some kind of exotic pipe bender gizmo? I watched a YouTube video about working with copper tube, and they used a tube cutter that scored the tube around and around until it broke off. Is that way better than a hacksaw? And, it looks like I also need to buy something to de-burr the newly cut end, right?
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Old 01-31-2019, 09:20 AM   #2
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A brake tube bender is <$15 at orielly auto parts Handles 1/8, 3/16, and 1/4 tube.
Tubing cutter is the tool to use. All but the cheapest have a deburr attachment.
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Old 01-31-2019, 09:50 AM   #3
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Don't use anything but a tubing cutter; they are inexpensive and easy to use. Debur tool should be built in. There are a few ways to bend the tubing correctly. I have a couple of different tools for that and both were inexpensive. Google "brake line bender" and "tubing bender springs" for ideas. The goal is to not kink the stuff.
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Old 01-31-2019, 09:54 AM   #4
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To expand a bit on High Wire's post above, a set of tubing benders that will do a medium radius bend can be bought for about $11. See https://www.amazon.com/Superior-Tool...er+tube+bender

A tubing cutter is much better than a hacksaw and is essential if you are putting a flare on the tube. Here is one for $13: https://www.amazon.com/RIDGID-32975-...r+tube+cutters. If it doesn't have a deburring blade, just use a screw driver blade or knife to take out the burrs.

If you are using compression fittings that is all you need. But if you need to make a flare you need a tool like this: https://www.amazon.com/Neiko-20656A-...e+flaring+tool

That tool does single and double flares but I suspect you only need a single.


I am sure that if you google you will find videos of how to use these. The only one that is a little tricky is the flare tool. Do a couple of practice flares first.

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Old 01-31-2019, 10:36 AM   #5
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Diesel is slippery stuff and can get through and leak where water and other liquids won't. All of the advice above on benders and cutters is spot on. I'll add a bit more in case you have any problems with pesky leaks after the installation.

  • Over working the copper. Bending, messing with flares etc will work harden the copper. It can easily be remedied by annealing. Heating with a propane torch and dunking in water. Heat till it glows then immediately dunk in the water. Youtube is your friend. Annealing will some times cure the leaky flare as it softens the copper making it more likely to seal correctly. Do be absolutely sure all of the diesel is out of the tubing before you heat it.
  • You may need to double flare. Practice on some scrap first. I recommend annealing double flares because the copper has been hardened by the double flaring.
  • If you have to purchase any fittings only use the highest quality from a reputable supplier. The cheap stuff will drive you crazy trying to get it to seal up.
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Old 01-31-2019, 10:48 AM   #6
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What’s the prevailing wisdom of flare vs compression fittings for diesel? (Hopefully, not another anchor thread.)
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Old 01-31-2019, 10:57 AM   #7
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Years ago I started a thread on boatdiesel on hoses, tubing and connections for diesel service. For tubing the consensus was as follows, best to just ok: double flares, single flares and compression fittings. Ski as I recall said that he often uses hose double clamped to tubing and that worked for him.


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Old 01-31-2019, 11:41 AM   #8
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Quote:
Originally Posted by angus99 View Post
What’s the prevailing wisdom of flare vs compression fittings for diesel? (Hopefully, not another anchor thread.)

IMO compression might work but flaring is better, and its not hard once you do a couple.


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Old 01-31-2019, 12:00 PM   #9
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In my work and my home shop I use only Rigid cutters now. Went through the cheaper ones , some ok, some not. NOt worth the fooling around.

Use a small countersink to deburr the ID. A knife can work if you are NOT doing double flares but if you are doing double flares then use a proper deburring tool, countersink. I have used knives but don't like them, they do work but can be inconsistent especially for double flares.

I have hand bent small OD tubing but you must work the bend into the radius carefully in small increments as any kink will have ruined the bend. Also used a socket or piece or pipe/dowel but must be securely mounted.

There is a Youtube on this particular method.


Also:


This one shows inverted flares, nut is male threaded, but more typically in your application is a nut with a female threaded nut but either will work. You just need the appropriate adapter fittings. Both are double flariing applications.

one more: Shows several techniques and appears to be the best without me watching them all.




The vise mounted pin bender is available from Lee Valley Tools OR Veritas.

Anyway, these Youtubes will get to a bunch more which should may help.

My own suggestions for diesel applications and brakes is DOUBLE FLARE ONLY. Not hard just do a few on a scrap first. Do NOT use compression fittings.
A double flare tool will do a single flare but a single flare tool will NOT do a double flare. Get a double flare kit.



And do not forget to install the flare nut, whichever type you decide on, before doing the flares. They cannot be installed later over the flares or the bends. Do not ask please.
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Old 01-31-2019, 12:41 PM   #10
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I did my fuel system (almost no pressure) with simple hose and hose clamps. Did the steering (up to 1000psi) with Cu tube and single flares. Where things might flex (rudder cyl) that got hydraulic hose. Filled and bled the whole system and was surprised that there were ZERO leaks. Did the bends by hand. With a little care, you can do it without kinks.

Zero problems with the fuel hose, too. Much easier to run. Not sure if there are any rules regarding a heater needing metallic lines.
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Old 01-31-2019, 01:00 PM   #11
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There is a Youtube on this particular method.

Those were great videos. Thanks very much.
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Old 01-31-2019, 03:09 PM   #12
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A good trick to bend tubing without kinking is to fill it with soapy water and put it in your fridge. The frozen soapy water will give the tube a support when bending and will avoid kinks. The soap help the ice no to crack and bend nicely. This is how are made music instruments like trumpets etc.

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Old 01-31-2019, 07:28 PM   #13
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It's all easy, just remember to slip on the fittings before you make the flare!!!
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Old 01-31-2019, 08:39 PM   #14
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What’s the prevailing wisdom of flare vs compression fittings for diesel? (Hopefully, not another anchor thread.)
Compression is a poor choice for fuel, or for any use on board other than water. Vibration can cause the joint to loosen and leak. Flare joints are a far better choice.

Cutting should be with a tubing cutter. Hacksaw only if you're doing demo work to take it out and scrap it. After the tubing is cut, the burr run in by the cutter can be reamed with the reamer that's on many tubing cutters. I actually prefer using a box cutter to shave the burr off and make a nice smooth edge, particularly important if it's going to be flared. Not removing the burr can easily create a bad flare joint.

For bending, nothing beats a bending tool, they're not terribly expensive. If you try to bend it freehand, you'll end up with a kinked mess. If you need to bend close to a flare, make the flare before you form the bend, it will lessen the chances of deforming the tubing and making the flare difficult to make.

Some cutter have a groove in the rollers to help to cut off the flare when you forget to put the nut on first. It happens.
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Old 01-31-2019, 09:44 PM   #15
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There are many types of compression fittings. I wouldn’t recommend the cheap hardware store ones for anything. If you buy good quality compression fittings (Parker or Swageloc for example) they are great. They are available in brass or stainless.
I’ve used them on 6000 psi gas lines as well as the fuel lines on my boat.
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Old 02-01-2019, 01:06 AM   #16
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My forced air diesel heater came with 3/16" OD copper tube for the fuel line. I've never worked with this stuff before. It shipped in a 12" diameter roll. Can I put a smaller radius bend in the tube without having to buy some kind of exotic pipe bender gizmo? I watched a YouTube video about working with copper tube, and they used a tube cutter that scored the tube around and around until it broke off. Is that way better than a hacksaw? And, it looks like I also need to buy something to de-burr the newly cut end, right?

Surprised no one has mentioned this simple method I use to bend any soft or thin metal tube.
Just fill it with dry sand and put a stopper at each end of the tube then select the radius required from any robust object lying around your garage and bend it to that.
The sand stops the tube kinking. Done it with lots of diameters and different metals, simple and free.
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Old 02-01-2019, 10:52 AM   #17
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Surprised no one has mentioned this simple method I use to bend any soft or thin metal tube.
Just fill it with dry sand and put a stopper at each end of the tube then select the radius required from any robust object lying around your garage and bend it to that.
The sand stops the tube kinking. Done it with lots of diameters and different metals, simple and free.
I've done this with steel pipe and it works well.
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Old 02-01-2019, 12:20 PM   #18
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Just make sure to get all the sand out...
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Old 02-01-2019, 12:22 PM   #19
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To me it's well worth the cost of a tubing bender to not have to clean sand, water, and soap out of the lines and boat then finished bending.
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Old 02-01-2019, 12:46 PM   #20
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To me it's well worth the cost of a tubing bender to not have to clean sand, water, and soap out of the lines and boat then finished bending.
+2

There are solutions and there are workarounds. Workarounds should only be used when all other options are unavailable.

My thought is, if you need the tool once, you'll probably need it again. Any tool under $200 is worth owning.
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