Soft copper tubing?

[ALEX1952]

Another method to form a coil is to crimp and solder one end fill with cold water which is not compressible, then fold and tightly crimp the other this has been used up to 15mm Dia tube when making a still this is obviously done cold.
There have been a lot of comment regarding annealing copper unless I've missed it and I think it may be worth mentioning the method for the novice as it contradicts normal practice.
Heat to red heat, which can be a problem to recognize as when you take the heat away it cools quickly and loses colour. Next you quench in cold water (metal bucket) you can use air but is not as effective the faster you cool the softer the copper, it also gets rid of contaminants and oxide
After bending the coil it may be worth re- annealing if it is to be a stressed item thus reducing the chance of cracking.

 

[Jennifer Edwards]

Hi Shopgeezer,

I use a similar low melting point metal for bending copper tubing, it is called “Lens Alloy 136”.

In my telescope mirror grinding days I used it to mount my mirror blanks to a holder I had screwed to a tree stump that I used as my grinding pillar.

It is sometimes referred to as “Cerrolow”, and is very similar in alloy components to ”Cerrosafe” which is what I think several other posts in this thread have mentioned.

It melts 58 C, and boils off somewhere around 300 C.

When I am finished bending I melt it out then anneal the tubing to remove any brittleness that the bending process has caused.

The heat from annealing removes almost all of the metal as a vapour which I should point out is probably bad to inhale, so should be done under ventilation.

Cerrosafe is:

42.5% Bismuth
37.7% Lead
11.3% Indium
8.5% Tin

Melting point is 74 C

Cerrolow is:

44.7% Bismuth
22.6% Lead
19.1% Indium
5.3% Cadmium
8.3% Tin

Melting point is 58 C

I imagine you could just use Bismuth which I think is what is used in fire sprinklers and melts even lower. However I am not certain of its malleability for this application.

Just my two cents,
Jenny

 

[Jennifer Edwards]

I just found this link to Belmont Metals, they market a bending alloy:

https://www.belmontmetals.com/product-category/low-melting-fusible-alloys/

 

[John Antliff]

Finding enough space on my bench to do that would be a major problem!!!!

 

[Shopgeezer]

Interesting description of these low melting alloys on the Belmont Metals web page. I looked up the term “eutectic”. It relates to a mixture that melts at a lower temperature than any of the components. Belmont also describes non-eutectic alloys. I assume that these melt at the actual melting point of the major components of the alloy.

 

[Shopgeezer]

Hi Shopgeezer,


In my telescope mirror grinding days I used it to mount my mirror blanks to a holder I had screwed to a tree stump that I used as my grinding pillar.

Jenny

Another mirror grinder. I stem from the old grind it fast and mount it on a stick held up by pipe fitttings days. Its a long ways from there to the slick computer controlled scopes we use today. Also a long time since I could stay up all night. At my age I need my sleep.

 

[Jennifer Edwards]

Interesting description of these low melting alloys on the Belmont Metals web page. I looked up the term “eutectic”. It relates to a mixture that melts at a lower temperature than any of the components. Belmont also describes non-eutectic alloys. I assume that these melt at the actual melting point of the major components of the alloy.

Hi there,

I believe that the difference between eutectic and noneutevtic is that eutectic metals go from solid directly to a liquid whilst the others will soften first.

Jenny

 

[Jennifer Edwards]

Another mirror grinder. I stem from the old grind it fast and mount it on a stick held up by pipe fitttings days. Its a long ways from there to the slick computer controlled scopes we use today. Also a long time since I could stay up all night. At my age I need my sleep.

Since moving to the north east of England I find that clear nights for stargazing are quite rare. So many times I have set my alarm to view a meteor shower or some other phenomena only to awaken to an overcast sky!

 

[John Antliff]

That's one of the reasons I emmigrated to NZ, however when I got here there were so many more interesting things to do that star gazing took a back seat and has never recovered!

 

[cox24711]

I have heard that you can harden copper tubing by sandblasting it or brushing it with a wire wheel if you are concerned with pressure.

 

[John Antliff]

Shot peening maybe but I doubt sandblasting is either effective or desirable! The wire wheel also sounds a bit far fetched to me - can anyone confirm this info?

 

[WOB]

There is a difference between the various low temp alloys when used for bending. Cerrosafe shrinks slightly upon cooling and then gradually expands back to original cast size in about 30 min. This is not what you want for a bending medium. The problem is that the solid rod of metal inside the tube will break and slide away from the bend allowing the tube to collapse in the gap. The only way around this problem is to allow the Cerrosafe casting to age for 24 hrs. It expands gradually over this period and will eventually grip the tube wall well enough to allow safe bending.

Cerrobend expands slightly immediately upon cooling, gripping the tube wall tightly and staying that way. There is no breakage or slippage of the rod and bending can done easily and safely right away.

So, if you have Cerrosafe, it can be used if you wait a day after filling the tube. If you need to purchase bending metal, buy Cerrobend and bending can proceed immediately. I learned this stuff the hard way years ago.

WOB

 

[Rocket Man]

How to upload pictures directly to this forum?

 

[Cogsy]

How to upload pictures directly to this forum?

You can drag and drop pictures directly into your post as you are typing it and they will appear at the end of your post if you do nothing else. However, as you're typing your message, if you want to insert one just click on the button next to it and it will be inserted at that position. Then you can keep typing and add another, etc.

 

[Wizard69]

There is not much I can add to this thread other than I spent some time with a guy from Germany that bent some really complex hydraulic tubing with the dry sand trick. If I remember correctly the tubing was 50 mm diameter with a heavy wall. Heat was from a large Rosebud torch. Being young at the time i was really impressed with the precision the guy achieved.

Since this was like 35 years ago I think the sand fill trick is a well practiced method.

 

[Charles Lamont]

Couple of points: With most types of copper it is not necessary to quench when annealing. I am told the arsenical copper used in full size locomotive firebox plates does, but in model work we are unlikely to encounter it. Quenching does fetch scale off the copper though. Working in a heritage railway loco workshop, we re-anneal all the copper pipework at every major overhaul. Work hardened copper is more brittle and more prone to cracking.