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Author Topic: Bending brass tube  (Read 12341 times)

tigertiger

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Bending brass tube
« on: September 07, 2008, 06:34:00 am »

I have some small bore brass tube I want to bend.

I do not have anything like a pipe bender and am unlikely to be able to get such a beast. I am not sure they exist.

How can small bore 2-4mm pipe be bent without crushing. I only want to bend 90 degrees and a large radius is what I am after as I want to run push rods or rigging sheets through them.

Any words from the wise please?
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boatmadman

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Re: Bending brass tube
« Reply #1 on: September 07, 2008, 07:54:42 am »

TT,

There is a pack of small pipe bending springs available, most model shops seem to have them. I have some but have to confess I havent had much luck with them, also, it may be difficult bending brass, copper is easier.


Ian
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FullLeatherJacket

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Re: Bending brass tube
« Reply #2 on: September 07, 2008, 08:01:21 am »

Hobbies list the K&S Bending Springs at about four quid - their website can be found via the banner at the top of the Forum Homepage...... ;)
I have a length of soft brass tubing in my junkbox which seems to bend easily by hand without kinking. I must have bought it from a model outlet at some time, so maybe a bit of judicious Googling will find some for you.
FLJ
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tigertiger

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Re: Bending brass tube
« Reply #3 on: September 07, 2008, 08:15:50 am »

can it be softened by anealing?
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Roger in France

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Re: Bending brass tube
« Reply #4 on: September 07, 2008, 08:32:05 am »

Knowing you do not have easy access to things in China TT, I was going to suggest annealing and gentle bending. It would probably require more than one or two stages. I do not think bending springs (internal or external) would be possible on such small diameters bent at right angles.

Knowing how inventive and skillful the Chinese are do you not have a small, local engineering works which could help out?

Roger in France.
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Martin (Admin)

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Re: Bending brass tube
« Reply #5 on: September 07, 2008, 09:41:45 am »


Fill the pipe with dry, fine sand.
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Bunkerbarge

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Re: Bending brass tube
« Reply #6 on: September 07, 2008, 10:54:08 am »

Tiger, you definately need to anneal it, probably a few times.  The angle you want is not the issue here it is the radius that determines your likelyhood of sucess so keeping a large radius will be a big help.

Sand can work but the tube must be packed and then sealed at both ends.  The problem is that the sand must be perfectly dry otherwise the pipe will become pressurised as the moisture vaporises and it can then blow the plugs out while you are heating it.

If this is only for running rigging sheets would copper pipe do the job?  Infinately easier to bend and anneal and most of mine has been done carefully round a former in probably two or three stages.  The thing is as soon as you start to bend the pipe the metal work hardens again so you have to 'feel' for it firming up.  As soon as you feel this you have to re-anneal again.
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GG

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Re: Bending brass tube
« Reply #7 on: September 07, 2008, 11:22:43 am »

Tiger,  you could make a suitable former to bend the tube around, heat the tube to "red heat" then bend it around the former. Stop bending as soon as any resistance is felt, reheat the tube and repeat.  This avoids the work hardening effect.
Or, fill the tube with solder, ideally a size that will just fit within the tube.  Bend the tube around a former and the solder should prevent the tube from collapsing.  If the solder will not pull out of the bent tube, heat it to melt the solder but be careful where the molten solder goes.
If no solder of a suitable diameter is available then you could fill the tube with molten solder first.
I am assuming that the bend you require is many times the diameter of the tube.
If not, then you you could insert two close fitting steel rods from each end of the tube, not meeting but leaving a gap where you want the bend.  With the gap heated to a red colour and keeping the heat applied, the tube should bend easily.  Some experimentation might be needed before you get the desired shape.
With all things hot, care is always needed!
GlynnG
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Roger in France

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Re: Bending brass tube
« Reply #8 on: September 07, 2008, 12:19:51 pm »

Molten solder....what a great idea!

I love Mayhem, I learn more every day.

Roger in France.
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RickF

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Re: Bending brass tube
« Reply #9 on: September 07, 2008, 04:24:18 pm »

Rather than molten solder, why not slide a length of cored solder into the pipe - try and find some that's a tightish fit. You can always heat it after bending if it wont come out easily.

Rick
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Roger in France

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Re: Bending brass tube
« Reply #10 on: September 07, 2008, 04:26:33 pm »

I think  Glynn was suggesting the two alternatives.

Roger in France.
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Rex Hunt

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Re: Bending brass tube
« Reply #11 on: September 07, 2008, 09:52:44 pm »

Why not try vehicle brake pipe?

Rex
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RickF

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Re: Bending brass tube
« Reply #12 on: September 07, 2008, 11:50:12 pm »

You're right, Roger. Must read the posts more thoroughly!  :embarrassed:

Rick
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tigertiger

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Re: Bending brass tube
« Reply #13 on: September 08, 2008, 07:54:42 am »

Thanks for all the tips guys.

The reason for using brass is I have brass.
I have just arrived in a new city and it will take me time to find where things are. And this can take a long time.

For example the man in the electric store will not tell you where the autoshop it on the offchance he can sell you a toaster instead of new brake liners. ::)
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JayDee

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Re: Bending brass tube
« Reply #14 on: September 08, 2008, 12:53:44 pm »


Hello Tiger,

Very nice to meet you at Llanberis, I really enjoyed the whole Show, looking forward to the next one.
Bending Brass tube is very easy, IF, you do things right.

Annealing the Tube
An ordinary Gas stove, or a good source of flame that is similar to a stove will do.
Heat the tube to a just visible dull red, quench the whole tube quickly into cold water.
Do not clean, or bend the tube in any way, if it comes out of the water with a slight bend do NOT straighten it out.

You will need  a former to bend the tube around, for the examples I have shown in the photo, I used the handle of a sweeping Brush.
Set the former firmly in front of you, place the tube at the back of the former, with your fingers at each end of the tube,
 PULL and BEND the tube round the former.
Don't pull too hard, or the tube will flatten out as it bends, not enough pull will allow kinks to form on the inside of the bend.
Just needs a steady tension on the ends of the tube.

Bend the tube in one steady motion, if you have to stop while bending, do the annealing again.
When the bend is to your liking, then is the time to clean and polish if required.
The tube in the photo is 3.5 mm diameter and the open ends are 25 mm apart.
I have used them as Pulleys for years, not as good as a real ball raced Pulley, but a whole lot cheaper !!.

John,  O0  O0  O0
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SteamboatPhil

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Re: Bending brass tube
« Reply #15 on: September 08, 2008, 02:20:12 pm »

If only you had asked the question before we meet at Llanberis. I have some stuff called cerabend, its a metal that melts in boiling water, great for any size any shape tube and re-usable.
All my other tips have already been posted (and I thought I was smart using the solder trick) With the sand, I use silver sand, baked in the oven for about and hour, let it cool in the oven (no moisture in there) then its ready to use.
Of course cerabend is much easier-------- O0
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Reade Models

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Re: Bending brass tube
« Reply #16 on: September 08, 2008, 03:13:07 pm »

I have some stuff called cerabend, its a metal that melts in boiling water

Years ago we used to use a low melting point white metal called Ceramatrix - I guess that yours is from the same stable?  Is it still available?

Malc
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SteamboatPhil

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Re: Bending brass tube
« Reply #17 on: September 08, 2008, 05:12:14 pm »

Hi Malc, yes I'm guessing its the same thing, I gather that apprentices used to make tea spoons from it as a joke, and watch as tea was stirred and the spoon dissapeared.
If you need details let me know.
Phil
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wideawake

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Re: Bending brass tube
« Reply #18 on: September 08, 2008, 06:35:46 pm »

Yes I think the same stuff is known as Wood's Metal.    The other method I've used successfully for reasonably shallow bends is to use external bending springs.  Among other suppliers they can be had from

http://www.chronos.ltd.uk 

Search for item no. TBS1

Cheers

Guy
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wideawake

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Re: Bending brass tube
« Reply #19 on: September 08, 2008, 07:16:52 pm »

Following up my own post - external bending springs on ebay item 120302010481

Guy

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