Problems bending 3/16" dia copper pipe without kinking

Hi - I am having problems forming a smooth 'S' bend in 3/16" dia copper pipe (ex EKP supplies) for my boiler top feed arrangements. I want to put a bend in at one end of a relatively long pipe run, (24" in order to keep the number of intervening joints to a minimum but am having the usual problems of flattening on the inside of the bends despite using a conventonal pipe bender. With short lengths I would usually use a low melting point alloy which overcomes the flattening problem but this is not so practical on longer lengths of pipe. Any suggestions that might be improve my chances of success?

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Have you annealed the tubing?

Can you get those wound steel coils that go over the outside of the tube and hold it in shape as you bend it with the next size up bender?

Yes, the tubing is being annealed before bending takes place. Have not considered using an external 'wrap' but the this might not be that easy on this size of tubbing.

No idea if it would work on tubing that small, but a plumber friend told me they used to pack dry sand into pipes and block off the ends with wooden plugs prior to bending. Might work, probably worth a try - if you do, and it does, please let us know

Rob

There is a material called woods metal that melts in hot water. This can be poured into a plugged tube, allowed to set followed by tube bending and then immersed in hot water to reclaim the woods metal.

If the tube is to be re-annealed or silver soldered then the woods metal must be completely removed.

Brian

What radius are you trying to bend?

Can you make a better pipe bender? There have been a few good ones in MEW over the years.

I do use Woods Metal on short lengths of pipe and it is very effective in avoiding any unsightly flattening of pipe. My current problem is wth longer pipe runs where Woods Metal would be more difficult to use but this may be the only recourse.

The 'S' bend being sought would have typically 3/4" centres to achieve the desired result

Rob, I worked with pipe fitters who used the sand and wooden plug method on steel pipes up to 3" NB that were also bent hot. They had to have a couple of people to bend it before it cooled. The wooden plugs were burnt out afterwards. For small copper tube have you tried filling with water and freezing before bending? Cool the tools as well and wear gloves to avoid heating the parts. Cool from one end to avoid bursting the tube with ice. Do a test piece before the real thing.

Martin C

Forgot to ask, what is the wall thickness? 

Bend tooling calculator

Edited By Martin Connelly on 30/05/2020 13:15:19

I’ve used one like THIS over the last 50 years. Mine cost about 17s 6d (maybe less?) and my example was likely less than that.... Never had a problem with car brake pipes.

Photo of current pipe bender

I think at least you need a former on the back of the tube as used on plumber's 15/22mm bending tools.

Martin C

Update - Have decided I might be pushing my luck with 26g tubing ((ex EKP) and have ordered up some 22g (ex maccmodels) as an alternative.

Go to Breckland Scientific they sell Fields metal which is the same as Wood`s metal

The tube you have has a wall thickness factor of 10 and the bend is 4 x diameter (4D). Using a bending machine with tooling shown on the Addison cardboard calculator in the link shows no need for a mandrel or wiper die. This means you should be able to bend it satisfactorily with a follower die to hold the correct shape on the outside of the bend. I think increasing the wall thickness will not improve the bends. I spent over 30 years as support engineer for a pipe shop so have a lot of experience sorting out problems with bending pipe and tube with hand benders, press benders and draw benders (manual and cnc).

Martin C

I wonder if you could fill it with water, freeze it and then bend. Or possibly a sugar or alcohol solution which would freeze to slush.

Adrian

Edited By AdrianR on 30/05/2020 16:25:52

You could try salt instead of sand, do the bending and flush out with hot water after.

Gren.

I am told that at Swindon Works they poured hot bitumen into the copper pipes, let it set, do the bending the burn it out. I assume thats how they bent the S bends on the inlet pipes to the Kings and Castles. I have packed dry sand into pipes, crimped the ends up, then bend it to shape, cut the pipe and remove the sand. Obviously the pipe needs to be longer than required to accommodate the crimped ends.

I am told that at Swindon Works they poured hot bitumen into the copper pipes, let it set, do the bending the burn it out. I assume thats how they bent the S bends on the inlet pipes to the Kings and Castles. I have packed dry sand into pipes, crimped the ends up, then bend it to shape, cut the pipe and remove the sand. Obviously the pipe needs to be longer than required to accommodate the crimped ends.