# Bending brass tubing



## stevehuckss396

Tried bending brass tubing. Failed! This is the brass tubing from the hobby supply that telescopes.

9/32 (.281) tubing.
Anneled it.
Filled it with bismuth.

When i try to bend it, it cracks the tubing right off. When i try with the tube empty, the tubing just folds right up. 

Should i try some other tubing or maybe some half hard copper?

I have seen alot of bent tubing on this board. What type of tubing are you using?


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## bentprop

The brass used by K&S and the like seems to be a very hard grade.It is very hard to bend.
Annealing it should have made it soft enough though.Did you let the tubing cool naturally before trying to bend it?
Most of the tubing used in model engines is likely to be copper,which anneals much easier,making bending less of a risk.I have succesfully bent K&S copper tube after annealing.The alternative is your automotive supply,they sell copper tubing off the roll, for use with gauges etc.


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## stevehuckss396

bentprop  said:
			
		

> Did you let the tubing cool naturally before trying to bend it?



Yes I did. I think I am going to order some copper tubing and try again.


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## shred

I'm a beginner too in small-scale tubing-bending and all of it was copper; a few by hand, a few with the bender. Annealed it's not too bad but even so the thinwall stuff from K&S was definitely trickier to work with than thicker-wall material. You may also be putting too tight a bend radius into it, and/or trying to bend it too much in one whack but I have no idea where in Machinery's Handbook that info would be (It's gotta be in there somewhere.. )


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## steamer

I use 1/4 5/16" and 3/8" copper with a similar bender and have had good luck

It's the tubing usually used for refrigeration.

I've bent the K&S stuff by filling it with solder..... :-\

Hope that helps Steve

Dave


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## jthulin

I have used K&S copper tube, 1/8" OD, and had decent success forming around concave "wheels" or dies. The key is to anneal often. Make a small bend, anneal, bend a little more, anneal, when in doubt, anneal. You can actually feel the work-hardening with a little practice. I agree too that you have to keep the radius big enough to avoid kinks.

Keep at it, you will get it woohoo1


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## itowbig

what about that method with filling it with soapy water then freeze it then bend it.


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## steamer

Generally the radius is not to be less than 4X the tube diameter.....but I have seen much tighter done. I believe the wall thickness in the bend thins out too much if you much below, but for low stress parts, I would guess it doesn't matter


Dave


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## arnoldb

I've used fine sand packed into thin copper tube to bend it - would this also be an option for the brass tubing ?
Needless to say, careful cleaning is needed afterwards.

Regards, Arnold


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## abby

I have found the best results are obtained by filling the tube with dry sand and sealing both ends. The crystaline nature of most low melt alloys results in cracking as the alloys are not malleable. if a tiny pin hole is left as a vent ,the sand filled tubes may be heated to make tight bends easier. the sand should be well packed into the tube with no space left or the tube will flatten.
After bending cut off the ends and the sand is easily removed with compressed air.
Hope this proves useful !


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## abby

oops crossed posts lol!


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## gilessim

I managed to bend some 4mm brass tube with a former turned from ally with a straight groove, 4mm x 4mm, so the tube fit in nicely, it doesn't need to have a radius in the bottom, you just need to stop the sides pushing out, I got my tube from a model shop so it may be a softer grade than yours but worth a try!

Giles


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## bearcar1

There is also the option of very tightly wrapping the tubing in 26ga copper wire about 1.000" before and after the central point of the required bend and securing the ends with just a touch of solder to keep the wraps intact. Make the desired bends and have t it. ;D

BC1


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## Bluechip

Folks

Don't know if this will work in small sizes, but ..

When I was at work I watched a 'Tube Bending Shop' in action.

They used solid formers, just less than the tube bore, with polished hemisperical ends. One bit was put in the tube up to the bend start and left there. The other was inserted up to it, as the tube was bent the second former was 'squeezed' out by the action of the tube internal wall pushing it. I had a bit of a go, it's fairly easy. It was about 1/2 " tube, about 10g wall, the formers were lubed with soap I believe. My effort was not up to the standard of '45 yrs. in the job' operators. It should be a simple job to try it. Stuff we have hanging about..
I've thought of trying it in the home shop, but never have.
You can feel the moving former wanting to be 'extruded' as it were, 

The hemispherical ends are in the tube, of course, not the outer bits .. 

Dave

EDIT A bit more.

Obviously, if there is a bend already in the tube, you can't get two in. I watched them do the job with just the free former used. I did not have a go at that bit. The formers were polished. Whether they were made like that, or just polished by centuries of hand wear, I don't know. There was an ancient air about the place.


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## cobra428

Steve,
I've used this type of bender and they work pretty good. See if you can find a tension spring with the right internal Dia, for your tube

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXR791&P=7

Tony


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## Bluechip

Tony

They look like the ones I have. Work well up to a point but .... too b****y short, and the wire is circular cross-section. I have a pair of 1960's UK made bending springs for 3/4" & 1" conduit. These are made from 'rectangular' cross section steel but the edges are concave on one and convex on the other. They have to be bent thro' about 30 deg. until the coils separate. Otherwise they seem to slide around each other. I surmise that the others, if not very close to the tube bore, allow a slight kink in the tube, the round section spring then binds up, et voila, I'm stuffed.
I've never found a source of better/longer ones.
I have used them with a bit of string to retreive 'em.
Miserable business if it lets go !! . 

Happened two nights ago. 

But then, I'm not the worlds most competent tube strangler 

Dave


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## SignalFailure

How about bending it hot using an inverse version of this simple gadget? Never tried it on tube but it might work....

http://sites.google.com/site/collec...gineering/tips---techniques/bending-round-bar


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## cobra428

Try this site. I always quench in water and it worked for me to sofrten the brass

http://www.vac-u-boat.com/bending_stiff_brass_tubing.htm

 works for copper too

Here's an article from a metallurgist

http://www.evergreengardenworks.com/copperwi.htm

Tony


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## stevehuckss396

cobra428  said:
			
		

> See if you can find a tension spring with the right internal Dia, for your tube




That is part of the problem. The tubing i am bending is .281. I chose the size to keep a 1/4 inch ID. This is a very odd size.

I just spoke to another fellow that enjoys this hobby and his bender has 1 inch OD rollers. I might make bigger rollers and try try again.


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## 4156df

I've had good luck with something like this:







Turn the groove to the depth and width of your tube OD. The bottom of the groove is the diameter of the bend. Make it a snug fit. As you bend, the sides of the groove keep the tube from spreading and collapsing. In the photo, the tubing is 0.125" OD and the bend diameter is 0.500".

Dennis


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## gilessim

Dennis, thats exactly the method I was trying to describe, only your photo says it all! unfortunately my camera is still being fixed, anyway that worked very well for me too!

Giles


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## stevehuckss396

I tried something like that with no luck. It did work on some 1/16 I bent for the overflow tube on the radiator.


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## 4156df

Giles,
You described the method very well. I should have referenced your post with my photo, and would have, but I completely missed it. Sorry.
Regards,
Dennis


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## stevehuckss396

Tried again today, failed!

The tubing was annealed and filled with salt. The tubing bent way better than the metal filled tubing. I think the problem may be that i am just trying to bend to tight. With a bit of math, i found that the inside bending radius is smaller than the diameter of the tubing.

I am going to try to build another bender with larger rollers and get the bend radius bigger than the tube diameter.

I almost had it!!


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## steamer

Steve,

Yes I would stay above 1 tube diameter for the ID Radius....definitely.


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## stevehuckss396

From what i have been reading, industry standard is 2-1/2 times the diameter of the tube, to the centerline radius. With the right bender type you can go alot less than that.

My dies were .75 in diameter. That would be .375 to the centerline. that is only 1.3 times.

The plan is to go to a 1.125 roller and that would put me at about 2X to the centerline.

I did make a bend on a 5/16 bender. The bend was very smooth but the tubing did "egg" being the shoe was to wide. That is why i think the increase in radius would help out.


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## steamer

The standard for Boiler tubes is a radius of 4X diameter....MIN.

Other wise you get too much wall thickness reduction....


Dave

PS just sent you an email...amazing what you can find.

Dave


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## pete

I'm not 100% sure this will work but try making a partial bend then anneal, bend some more,anneal, repeate as required. Brass and copper work harden far faster than you would expect so what may??? be happening with such thin walled tube is it is work hardening part way thru the bend

Pete


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## onetimeguy

This is a bit late but I just stumbled across this thread. It may not help your situation since it seems like you have tried other things, but bismuth causes embrittles copper horribly. That's why the tubing cracks off when you fill it with the bismuth. The same thing happens with any copper alloy (brass, bronze, etc). 

Here's a tidbit from an abstract of a paper, although there's lots of information on this.
http://adsabs.harvard.edu/abs/2004APS..MARP32001C


Hope this helps someone in the future!


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## Engine maker

I finished up a Morton M-5 last year and had to bend 3/16 bass tube with 3/16 radi for the intake pipes with good success. First I annealed the tubes. I was lucky because I had a fire in the fire place the night before and had a whole bucket of ashes. There were still even some burning embers left. I just put the tubing in the bucket of ashes and completely covered the tubing. I let it sit till it was completely cool. About 2 days in my case. When the tubing came out it was no stronger then 16Ga. copper wire. I then filled the tubes with a product called cerrobend (you can also use cerrosafe one melts at about 125 degrees and the other at about 145 degrees.) You can get small bars on e-bay. After that just take your time and bend away. I would suggest you bend around something just to get things uniform. When done you can either drop the part in hot water or just hold a torch on it for a few seconds and out it comes ready to be used again. Here's a a pic of some of the bends.

Jim


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## kustomkb

Wow Jim! nice engine, paint looks pretty sharp too!

Why not post a few more pics in the gallery section.

-Kevin.


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## cobra428

Very Nice Engine Maker. I already told you about my dads M-5. 
Tony


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## ChooChooMike

> I finished up a Morton m-5 last year


Jim - how dare you taunt us like that with just a few pictures of that beautiful engine !!

We NEED some pictures of it - especially a video of it running :bow: :bow:

 

Mike


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## Engine maker

I"ll probably never run it again. Built it to original 1940's drawings and a lot of the original parts are too weak. Broke push rods on the first run. Not real proud of it for that reason, if it can't be run what good is it. May built another someday with updated parts.

Jim


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## zeeprogrammer

Engine Maker  said:
			
		

> if it doesn't run what good is it.



To admire.
To inspire.
To learn from.
To...I don't know...experience in many ways.

It's a beautiful engine. Whether it runs or not...there's a lot of good about.
I'm glad I saw it. I was impressed...if that means anything.


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## steamer

Jim,

Beef them up! ;D.......Persistence my friend....it will be fine.


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## vlmarshall

No kidding! Fix what breaks and run that beastie! :bow:


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## Engine maker

Well talking to people in the know, you beef up the push rods to 3/32, then the rocker arms fail. Beef up the rocker arms and the connecting pin between the front and rear crankshaft fail. See where this is headed. Easier to start over and build in all the updates.
Some day?


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## vlmarshall

Ah, that's awful.
However, real-world engine building is the same way...at least when you start adding performance goodies.

 What's wrong with the rocker arm geometry? Springs too stiff? Ratio too high? Cam profile too severe? Something must be wrong or the rockers wouldn't be in an "Us-or-Them" battle with the pushrods.

Fixing it sounds like it'd be fun, and that's where I'd head before replacing the engine.


Edit: Besides, I want to see it running! ;D


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## Gatman44

For bending thin wall brass tubing try anealing it and filling it with Bismuth. Works for me.


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## vlmarshall

Gatman44  said:
			
		

> For bending thin wall brass tubing try anealing it and filling it with Bismuth. Works for me.


I really HAVE to try that, I have a lot of low-temp alloy left over from some miniatures casting I used to do.


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## VirginiaGuy

You have to heat it to barely glowing red hot in dim light.


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## Tin Falcon

IIRC  k & S sells spring benders as well. 








Only a couple dollars

http://hardwareonlinestore.com/

Wow that was an old thread that was dug up !

VirginiaGuy please post an introduction in the welcome area.  and tell us a bit about yourself.

Tin


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## beazld

I bend 1/8" brass tubing by first annealing it then putting a piece of plastic weed eater string thru it, that keeps it from collapsing when bending,. Then pull it out when done.


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## stevehuckss396

Hello Fellows!!

I saw this post brought back to life and I sort of had to laugh. I posted this over 5 years ago. I'm happy to report that bending tubing is not a problem anymore. I typically make a shoe for the tubing size. I also switched to stainless tubing because it looks great after a good polish and bends easily.


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## davidyat

I haven't used it but I hear Cerrobend could work in bending tubing. It's a low melting metal. It melts into liquid form at 158 degrees Fahrenheit. If you can find a stick of it that will fit into your tubing, stick it in and with one end capped somehow, put it into a pot of boiling water. After it solidifies, bend your tubing and stick it into boiling water again to get the Cerrobend out.

https://www.ebay.com/itm/Cerrobend-...IoAAOxyc2pTaiqe:sc:USPSFirstClass!46123!US!-1


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## deverett

I've heard that it is a good idea to 'line' the pipe with olive oil or similar to ensure that there is no residual CerroBend left afterwards.  Or was that when using other types of filler?!

Dave
The Emerald Isle


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## bobden72

I have used Cerrobend quite a few time and can say without a doubt its great.  Don't forget you still have to anneal the tubing before.


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## Cogsy

deverett said:


> I've heard that it is a good idea to 'line' the pipe with olive oil or similar to ensure that there is no residual CerroBend left afterwards.  Or was that when using other types of filler?!
> 
> Dave
> The Emerald Isle


I use the olive oil and it was my understanding that it's to prevent the cerrobend sticking to the wall of the pipe while you bend it. If the cerro is stuck firmly to the pipe it can fracture as you bend the pipe and leave 'steps' in your bend. With it's low melting temp I wouldn't expect the cerro would be a problem to get out of the tube even without the oil layer.


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## bluejets

stevehuckss396 said:


> Hello Fellows!!
> 
> I saw this post brought back to life and I sort of had to laugh. I posted this over 5 years ago. I'm happy to report that bending tubing is not a problem anymore. I typically make a shoe for the tubing size. I also switched to stainless tubing because it looks great after a good polish and bends easily.



Hi Steve,
                   Do you have any detail on the tubing sizes and where you manage to get it from?
Down under these things are hard to come by normally.
Maybe a tooling tip on how you make your mandrels if you get a chance one day.
Cheers Jorgo


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## WOB

Cerrobend is intended to "stick" to the wall of the tubing.  It does this by expanding as it cools.   If the rod of Cerrobend is allowed to slip as the tube is bent, it will break( it is relatively brittle) and slide, opening up a gap and allowing the tube to distort at the gap which is usually at the apex of the bend.  I learned this the hard way by trying to bend 5/16" soft aluminum tube with Cerrosafe that I had on hand.  Cerrosafe  does not expand on cooling until some time has passed and then not very much long term.  I found that if I aged my Cerrosafe filled tube for 24 hours  I then could bend them safely.   Cerrobend allowed immediate bending on cooling and I could get on with the job.   Well worth the additional small expense. 

WOB


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## Ken I

Here's a link to a bender I posted some time back....

https://www.homemodelenginemachinist.com/threads/wire-tube-bender.16140/

Regards,  Ken


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## stevehuckss396

George britnell also posted some plans for a super nice tubing bender. Do a search but I think they are in the files archives.


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## stackerjack

deverett said:


> I've heard that it is a good idea to 'line' the pipe with olive oil or similar to ensure that there is no residual CerroBend left afterwards.  Or was that when using other types of filler?!
> 
> Dave
> The Emerald Isle


Another idea is to use electrical flex. Remove the outer sheath from a suitable piece of electrical flex then cram as many strands as possible inside the tube, as tight as possible. Bend the tube, then withdraw the flex one strand at a time.
Jack


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## bluejets

stevehuckss396 said:


> George britnell also posted some plans for a super nice tubing bender. Do a search but I think they are in the files archives.



So do you have any detail on the tubing sizes and where you manage to get it from?


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## bobden72

deverett said:


> I've heard that it is a good idea to 'line' the pipe with olive oil or similar to ensure that there is no residual CerroBend left afterwards.  Or was that when using other types of filler?!
> 
> Dave
> The Emerald Isle


Dave never had a problem getting the CerroBend out of the tube.  Instructions don't mention a release agent.


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## kquiggle

Here are some "official" instructions for using cerrobend:

http://www.csalloys.com/how-its-made.html​
Here's an excerpt, but check the link for additional details and useful information:

*Directions for bending thin walled tubing with CS Alloys*

Make sure that tubing is fully annealed.
Clean interior of tube with pull-through to remove any scale or foreign matter.
Tightly plug one end of tube with wood or rubber plug.
Fill tube with a light grade oil, preferably S.A.E. 10.
Pour oil from tubing leaving a small amount in the bottom of the tube. Careful attention to oiling is necessary to prevent the CS Alloys “tinning” the tube.
Fill tube with CS Alloys from an iron ladle or a welded stainless steel container suspended in boiling water or hot water jacketed stainless steel tank, allowing the alloy to run down the side of the tube in order to avoid air pockets. Small tubes (1/4” dia. or less) should be placed in boiling water while being filled.
Lower loaded tube immediately into a cold circulating water quenching tank and leave for sufficient time for tube and filler to attain room temperature throughout (About 15 minutes for 1” diameter tubing, 20 minutes for 1-1/2” diameter tubing, etc.).
After proper quenching, re-warm loaded tubes to about body temperature.
Remove plug from tube.
Bend loaded tube with a slow uniform pressure over a forming block or in a regular bending machine.
Immerse bent tube in boiling water tank (stainless steel preferred) and allow CS Alloys to run out (Do not use torch). Tilt and shake tube as necessary to remove alloy as completely as possible.
Plunge unloaded tube, while still hot, in cold water for two minutes to solidify and small drops of CS Alloys retained in the oil film.
Flush tube with a cold grease solvent to remove oil film and any solid particles of CS Alloys. Additional cleaning may be done with a tight fitting pull-through.
Important: Satisfactory results depend entirely on rapid quenching and thorough cooling, re-warming before bending, and using a slow uniform pressure during the forming operation.​


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## WOB

These instructions are overkill for the small tubing used by modelers.   Aluminum and stainless tube will not "tin",  so do not oil them.   I have not used Cerrobend on copper or brass tube, but at the low temps. involved, I do not see how tinning could occur.   Also don't need the elaborate cooling procedure.   Simply cool to room temp. and bend them.  After bending and immersion in boiling water, simply push a pipe cleaner through the tube and any residual metal will push out.  Most of the time here will not be any left in the tube.

WOB


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## stevehuckss396

bluejets said:


> So do you have any detail on the tubing sizes and where you manage to get it from?




https://www.homemodelenginemachinist.com/threads/tube-bending-radius.7810/#post-86271


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## kquiggle

WOB - you make some very good points.  

My starting assumption is that the guys who make and sell Cerrobend must know something about how to use it, but it's also good to bear in mind that their target audience is not the hobby machinist. I think this is true in many cases, where advice or instructions developed for production environments have to be adapted or modified to fit the home workshop. However, I do think it is useful to have a solid and well informed starting point, and then adapt as necessary.

Now that I have read the Cerrobend instructions, I better understand why oiling is necessary in some cases (and as you rightly point out, not always needed). It is in any case an interesting alloy and I had fun learning more about it.


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## doc1955

Here is a vid on my bending brass tube for the first pipes I made for the Little Demon engines. I used a corn meal packing too keep them from collapsing while bending plus annealed before bending.


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## goldstar31

One of the most informative U Tube things is the How it's made one on making French horns.  They use a form of pitch( pun not intended) instead of an alloy which melts at 70C from Fry's Metals. It's in one of my late wife's huge library on music.
However, the video which I clear ly like is how to remove dents and kinks in tubing by forcing a number of correct diameter ball bearings  into the damaged tube.


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## Badhippie

Back in the day we used to cap one end of the tube then fill it with water making sure to leave enough room for expansion. Then put the tube in the deep freezer and let freeze. Then using a tubing bender or a Mandel bend the tubing how ever you need it. This works great on thin wall tubing if you have the time


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## john_reese

Sometimes it is necessary to start with a longer tube.  You need enough length on the back end to get a firm hold and enough to establish the tangent at the end of the bend.  The excess can be trimmed off after the bend.


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