Can I anneal copper pipe with a propane torch? - RC Groups
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May 23, 2010, 11:53 PM
Grumpa Tom
Kmot's Avatar

Can I anneal copper pipe with a propane torch?

I need to make an 8" diameter ring of 1/2" diameter copper pipe. I will make two 180 half rings and solder them together. I wanted to get some "soft copper" but it is only sold in large rolls at my home improvement store. So I bought a 5' length of regular 1/2" copper pipe. I would like to try to anneal it so that it will be easy to bend. Has anyone done this using a propane torch?
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May 24, 2010, 01:06 AM
Registered User
steveciambrone's Avatar
Propane will work fine to anneal the copper pipe, you will have to anneal several times while you try to bend it. Anneal/bend a little/anneal again/ bend a little and repeat. You should have a form to bend it against. so long as you get the copper red hot then let it cool it will bend.

May 24, 2010, 01:37 AM
Grumpa Tom
Kmot's Avatar
Thanks Steve.
May 24, 2010, 01:51 AM
Registered User
jaguar75's Avatar

Question Can I anneal copper pipe with a propane torch?

I am a pipe fitter and can tell you that it is very difficult to bend tubing but you can create a perfect radius bend with a near perfect circular inside diameter.When building a trombone an annealed copper tube is filled with soapy water and frozen,then it is bent in a tubing mandrel.After thawing it is then filled with a steel ball bearing that is the size of the inside diameter of the copper tube then pushed through with smaller diameter ball bearings.You can solder a male adaptor on one end of the tubing and thread a test guage on and use compressed air to force the steel balls through.
Good luck.
May 24, 2010, 10:12 AM
Just call me "Mo"
mogogear's Avatar

You can slide the pipe one small section at a time over a burner on your kitchen stove if you have a gas stove..That could save some propane if you need to.

I do this when I have several things to anneal - I just lay them on the grate over the burner

good luck!
May 24, 2010, 11:30 AM
Grumpa Tom
Kmot's Avatar
Thanks guys! I am going to try this guys method of bending:
May 24, 2010, 12:57 PM
3 Blades to the Wind
Shaun Hendricks's Avatar
I bent some 3/8" hard copper tubing with a tubing bender from HF and a lot of practice! I found the right combination was to:

1. Hammer one end of the tubing flat closed
2. Anneal the tubing (pass 1)
3. Fill tubing with fine sand (I used paint texture sand, very fine)
4. Hammer the other end flat closed (crushing the sand out of it and into it- packing the sand)
5. Anneal the tubing (pass 2)
6. Bend in 45 increment
7. Anneal the tubing (pass 3)
8. Repeat steps 6 & 7 until desired degree bend (or coil) is reached.
9. Cut off flat end with tubing cutter
10. Pour sand out
11. Cut each end to length

I have successfully bent 180 segments this way. I could do a coil but that would take a modification to the bender to allow it to 'spiral' out a coil. If you go slow and patiently, it actually goes easier. If you rush it, you'll flatten the tubing and have to start over.
May 24, 2010, 11:29 PM
Grumpa Tom
Kmot's Avatar
I built a form. I annealed the tube end, and started to slowly apply pressure to bend it around the form. It immediately collapsed and flattened!

Remebering I had read about people using sand or salt, I went looking for salt because I didn't have any sand. Didn't have enough salt to fill the tube so I thought I was going to have to go to the market. Then I remembered I had something else. Glass beads, for my blast cabinet. I broke off the flattened end, and soldered it shut. Then I filled the tube with the glass beads, and tapped it to pack it tight. Filled it up again and crimped the end and then soldered it closed.

I then tried to bend it. Wouldn't budge very much. I realized then that I would still have to anneal it. So I did, and slowly worked my way around the form. Success! I got a nice 180 wrap around the form and the tube did not kink.

So I started on the opposite end, of my 5' long piece, and did the same method. This time it flatted as soon as I started to make the bend. What the heck? I re-annealed further down and tried again and it flatted again!

Thinking the glass beads had leaked out, melted, or something, I cut the tube off at the bad end and was surprised to see it had still been full and a lot of the glass beads spilled out. So I soldered it closed again, making sure it was full of beads. I then tried annealing but at a slower rate, and longer amount of time with the torch. And I started bending it around the form even slower than the first time. This did the trick, and eventually I got another 180 bend I can use. It is not as perfect as the first one, it has a very small flattening that started but it is not too noticeable.

So I thought I would use my tubing cutter to open the pipe up and the copper must have still been way to soft becuase the tubing cutter crushed the tube where I was trying to cut it!

I ended up using a hobby razor saw to cut the ends. I did finally end up with the two pieces that I can use to make my ring muffler. I will be able to round out that one end that got buggered, and I will connect the two halves with short pieces of coupler.

If I do this again, filling the tube with sand/glass beads/salt is the way to go. Next time I will tamp it down even tighter by mechanical methods instead of just tapping it on the ground. And I will heat it in a dark place so that I can see if the copper pipe is actually getting red or not. I was in the outdoors today with sunlight and wind.

It has been quite a learning experience today!
Last edited by Kmot; May 24, 2010 at 11:35 PM.
May 25, 2010, 12:23 PM
3 Blades to the Wind
Shaun Hendricks's Avatar
That's why when I use sand, I hammer the second end shut and hammer up the tube until I get no compression of the sand, I know it's "packed" at that point. I also found that slow is the way to go...
May 26, 2010, 08:24 AM
Registered User
You NEARLY had a tube bender Kmot. Had you put a semi-circular groove in the "Pully" blank (Half the diameter of the tube) and the same in the straight block, by clamping a shorter piece of grooved straight to the side of the pulley, you could have "Rolled" the longer one with the tube between them.

When annealing COPPER, heat to bright red and Either let cool slowly OR quench in water. Bout the only metal that this works with BOTH ways.

Nother one to remember, SOME brasses (NOT Bronzes) don't anneal.

Regards Ian.
Last edited by Circlip; May 26, 2010 at 08:26 AM. Reason: Ref to tube Dia.
May 26, 2010, 10:32 PM
Grumpa Tom
Kmot's Avatar
My project turned out okay.
May 27, 2010, 11:31 AM
3 Blades to the Wind
Shaun Hendricks's Avatar
Is that some kind of burner?
May 27, 2010, 01:32 PM
Grumpa Tom
Kmot's Avatar
I thought the same thing when I looked at the picture, lol!

I suppose it could be a burner ring, for a very large boiler!

But no, it has nothing to do with steam or steam engines. I asked about annealing in this forum because I know people work with copper to make boilers and burners and other such stuff.

It is actually a ring muffler for a radial engine.
May 27, 2010, 01:54 PM
3 Blades to the Wind
Shaun Hendricks's Avatar
That's a pretty big radial engine! Nice job.
May 27, 2010, 03:08 PM
Grumpa Tom
Kmot's Avatar
Thanks Shaun!

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