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Bending small bore copper tube

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The Merry Miller21/03/2011 14:39:07
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Does anybody have info to hand in respect of the recommended minimum bend radii for small bore copper tube starting at 1/16" through to 1/4"
 
I appreciate that it will be different for annealed tube as opposed to "as drawn" and also will depend on the wall thickness.
 
I need to collect this data before I launch into designing and making my own set of bending equipment.
mgj21/03/2011 17:21:27
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Well the minimum bend radii are all specifed in the Hemming way kit, but are are by no means the minimum that can be achieved.
 
As for bending kit - the Hemmingway one is very good Has all the bends and a slipper and hook. Even better is an annealing torch and a few grooves of the right width and depth in a length of bar.
 
If I'm not telling my Granny, but all I do is bend a "template" out of soft garden type wire. I then copy that. I have now 4 different bars with the grooves in. I was going to build a little holder etc with a stop etc but up to 1/4" it isn't IMO worth the hassle. Fingers round the bar and annealed tube does a very professional job.
 
Obviously one doesn't bend tube as drawn? Surely?. One anneals first?
 
I have to bend some 3/8 tube for Metre Maid, but I don't see myself doing any more than putting a groove in another bar with a ball nosed slot drill!
 
Are you sure you are not in danger of making a very simple thing overly complicated?
 

Edited By mgj on 21/03/2011 17:22:51

Edited By mgj on 21/03/2011 17:24:30

Chris21/03/2011 19:00:57
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If it is of any help in me 4345 John Barrett had a design for a super little bender which was my first project. It has been used to make all the pipes for Northumbrian as well as several relacement brake pipes for the car.
Formers are easy to make to suit the size or profile of the material to be bent.
As my first project it took me a week of evenings to make but someone experienced could probably knock it out in a couple of hours.
The Merry Miller21/03/2011 19:55:08
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I must admit 'mgj' that the larger sizes of tube I have used in the past i.e 15mm & 22mm were always table X (half hard).
 
I've yet to find out what hardness grades are available in the copper tubes for model engineers.
 
I also want to make sure that my design is extremely simple.
JasonB21/03/2011 20:02:23
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There were some very simple benders in ME 4393, you can buy them on ebay Says they can bend a radius of twice the pipe dia
 
Jason
The Merry Miller21/03/2011 20:33:36
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Saw those Jason, good idea but with a fixed bend radius not quite what I had in mind, I could adapt the design though.
mgj21/03/2011 20:37:20
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How hard - doesn't matter does it? We usually want tight bends so we are going to anneal.
 
By all means make something, but truthfully, in sizes up to 1/4 inch thin wall tube, it's quite unnecessary.
 
I built the Hemmingway one, which is a miniature proper pender. You have a former for that dia of pipe, a slipper goes over the tube and hook holds the tube. A lever pulls the slipper round. Lovely thing, but it remains unused, after the first couple of bends. The only reason why I haven't offered it you you free gratis and for nothing, (so useful is it) is that I'm going in for a 4" TE which will need a bender for the exhaust pipe, since it is something like 3/4" dia and has a distinct back to back joggle.
 
Which begs the next question - how neat is my pipework on hte 3" engine. Well a number of people have commented on how tidy it is. - nice bends, neat straight runs etc. And the only tools - a few lengths of bar with some grooves in them, and a torch with which to anneal, and below 1/4" dia I personlly wouldn't waste time on anything more elaborate.
 
Or you can look at it another way - it is a bender, and about as simple and effective as they come.
 
Your choice, and good luck to you. I hope you enjoy making it, but before spending any effort on such an important and eminently useful item, try the other way. You might well end up saving a few evenings and end up putting them into something beneficial, like a model.
 

 
 
 

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