Problems bending 3/16″ dia copper pipe without kinking

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Problems bending 3/16″ dia copper pipe without kinking

This topic has 27 replies, 15 voices, and was last updated 14 June 2020 at 11:05 by Martin Connelly.

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30 May 2020 at 12:23 #476076
Greensands
Participant
@greensands
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&quot 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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30 May 2020 at 12:23 #1937
Greensands
Participant
@greensands
30 May 2020 at 12:25 #476077
Greensands
Participant
@greensands
The emoji was unintential!
30 May 2020 at 12:28 #476079
Hopper
Participant
@hopper
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?
30 May 2020 at 12:33 #476080
Greensands
Participant
@greensands
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.
30 May 2020 at 12:33 #476081
Grindstone Cowboy
Participant
@grindstonecowboy
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
30 May 2020 at 12:54 #476086
Brian H
Participant
@brianh50089
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
30 May 2020 at 12:57 #476088
Hopper
Participant
@hopper
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.
30 May 2020 at 13:01 #476091
Greensands
Participant
@greensands
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.
30 May 2020 at 13:03 #476092
Greensands
Participant
@greensands
The 'S' bend being sought would have typically 3/4" centres to achieve the desired result
30 May 2020 at 13:05 #476093
Martin Connelly
Participant
@martinconnelly55370
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
30 May 2020 at 13:06 #476094
not done it yet
Participant
@notdoneityet
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.
30 May 2020 at 13:11 #476096
Greensands
Participant
@greensands
Photo of current pipe bender
30 May 2020 at 13:20 #476099
Martin Connelly
Participant
@martinconnelly55370
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
30 May 2020 at 14:05 #476111
Greensands
Participant
@greensands
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.
30 May 2020 at 14:19 #476113
Donald Williamson
Participant
@donaldwilliamson36047
Go to Breckland Scientific they sell Fields metal which is the same as Wood`s metal
30 May 2020 at 15:54 #476133
Martin Connelly
Participant
@martinconnelly55370
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
30 May 2020 at 16:23 #476136
AdrianR
Participant
@adrianr18614
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
30 May 2020 at 18:01 #476156
Grenville Hunt
Participant
@grenvillehunt47315
You could try salt instead of sand, do the bending and flush out with hot water after.

Gren.
13 June 2020 at 23:05 #479698
Howard Snowden
Participant
@howardsnowden92695
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.
13 June 2020 at 23:06 #479699
Howard Snowden
Participant
@howardsnowden92695
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.
13 June 2020 at 23:43 #479703
Emgee
Participant
@emgee
Greensands

Do you keep the moving roller down tight to the fixed former when bending ?
Do the grooves make a complete circular shape equal to the pipe OD ?

If the above lines are true then with annealed tube you should get good bends at the radius required.

Emgee
14 June 2020 at 02:02 #479711
Simon Collier
Participant
@simoncollier74340
Make deep grooves with parting tool into which your tube is a very close fit. Anneal tube and bend tube by hand, with jig in the vice. This one is for 1/4 and 5/32 copper tube. The tube sides are constrained so cannot flatten.
14 June 2020 at 06:59 #479717
Alan Charleston
Participant
@alancharleston78882
Hi,

I've had success bending 1/8" copper tube by inserting a length of nylon strimmer line into the tube before bending. 1.65mm line is a snug fit. The line is removed after bending the tube using a metal plate with a 2mm hole drilled in it. The line is threaded through the hole and the end of the tube butts up against the plate. The line is grasped with a pair of pliers and levered out by pivoting the pliers against the plate. I can get tight bends with no kinking.

It's important that the line is removed after each bend is made as the resistance to being pulled out increases with each bend until it snaps off instead of coming out. Then you are up for heating the tube and applying compressed air until molten plastic is squirted across the workshop.

I'm not sure strimmer line is available in the diameter needed for 3/16" tube, but if it is, it might be worth a go.

Regards,

Alan
14 June 2020 at 07:21 #479724
pgk pgk
Participant
@pgkpgk17461
I made myself a wire bending tool a while back .while looking at ideas I came across one chap who made himself some bending buttons for tube with his blank in a vertical rotary table and the profile cut with the side of an appropriate endmill. He claimed this was easier than using a form tool on the lathe.

pgk
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