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?

 

[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.

 

[stevehuckss396]

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.

 

[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.. )

 

[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

 

[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

 

[itowbig]

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

 

[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

 

[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

 

[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 !

 

[abby]

oops crossed posts lol!

 

[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

 

[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

 

[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.

 

[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

 

[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

 

[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

 

[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

 

[stevehuckss396]

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.

 

[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