Flanging Boiler Ends

alan2525 · 07-02-2008

I need to flange the ends for a small copper boiler, approx 40mm diameter from 1.5mm copper sheet. External Fired copper horizontal loco pot boiler with no internal flue.

I was thinking that it'd be a dismal failure clamping the copper to a small steel disk and trying to hammer the edges to form the flange. I can see that swiftly ending in a nasty creased ugly piece of mangled copper fit for the bin. And my temper soon going down the pan too.

I also have access to a hydraulic press which seems to be a far nicer prospect. Give it a little press, remove and then anneal, press a bit more, anneal rinse and repeat! Remove finished flanged end and file the edges for a nice neat job.

The press is one of those 10 ton machine mart jobs with a hydraulic ram.

How best to make the press tools for the job? How would you keep the two parts of the tool in alignment as you use them, steel pins in the corners? I'd have thought a chunk of steel with a hole machined in it to the outside diameter and then a disk with slightly radiused edge of the internal diameter. What sort of clearance would I need to prevent the two from wedging up with the 1.5mm copper as it's formed?

Alan

**Bunkerbarge** · 08-02-2008

Never having done such a thing I can't be of much help but just thinking out loud I might generate some ideas for you.

I would make a male and female die, as you suggest, but think about what has to happen when you deform the metal. As you cannot create nor destroy matter it has to go somewhere so the basic principle is that the die must have enough clearance to allow for the volume of material in the plate.

Obviously the clearance at the sides must be at least the thickness of the plate but you are actually going to deform a much wider circle of plate into the flange so that excess material has to go somewhere. Basically I think you need a lot more clearance than the thickness of the plate!!

I would also make sure that you don't introduce any sharp corners so good radii on the plug and the female piece and obviously a dished shape would be strongest.

Just a few thoughts.

**GEEDUBBYA** · 08-02-2008

Howdy Alan,

Ok, now I am a machinist by trade, and I am sure there are several of us in the forum, that being said, what I have gotten out of your description you have an approx 1 1/2" dia. tube you need to flange on one or both ends.
I can see in my mind several different ways of achieveing (sp) this.

1. the method you mentioned with a press whereby you create a die and punch for the press.

2. creating a die and punch which can be used in conjuction with a hammer.

*3. cutting a flange and "silver soldering" it into place on the tubing.

**4. single piece construction using 2" dia copper rod in a lathe.

*In number 3 above, you would need to cut a flange the size required from a sheet of copper of the appropriate thickness using a lathe, "milling machine/flycutter combination" or even a vertical bandsaw (if precision is not really important) and then using silver solder (not lead) and brazing the flange in place on the end (or around the outer edge) of the tubing.
Silver solder is very strong and in my former occupation as a machinist building power distribution transformers, I often used it and have seen that the copper itself will fail before the silver solder joint fails provided it was brazed properly.
Now I will say that single piece construction would be "optimal", but failing that, the silver solder method would be the way to go. There is alot less "manufacturing" involved in the brazing method and depending on whether it was a butt joint or the flange was slipped over the outside edge of the tubing would really make no difference....again, the silver solder joint, if brazed properly will be stronger than the copper.
One other aspect of the silver solder brazing method i should have mentioned above is that the solder will fill any void you may have between the two pieces of metal and being silver, it will have a much higher heat tolerance than ordinary tin or lead core solder (upwards of something along the lines of approx 1200° F).
The only drawback I might see in this method would be the availibilty or lack thereof.....of an Oxy-acetlyene torch. You will need this in order to use the silver solder.

**In number 4 above, would be the construction of the tube with flanging on the ends as needed by constructing the entire one piece unit on a lathe using 2" dia. round copper stock.
You would turn down the external dimensions as required including both flange thicknesses, seperating the piece from any excess stock, "re-chucking" the entire piece then "boring" the internal dia. as needed, allowing you to create as thick or thin a wall as you want.

Now lets say you dont have a lathe or an acetylene torch, I am sure that a local machine shop would build this boiler, flanges and all, to your specifications, for a few dollars plus the cost of the small piece of copper rod (which would only have to be a piece of scrap that you can pick up at a salvage yard).

Like bunker said, these are just a few thoughts, there is always the method of "rolling" the flange onto the tubing using a lathe, but that is way to hard for me to describe much less instruct someone on how to achieve the desired results. And not knowing your machining abilities, I wouldnt even begin to try to explain it.

I hope this has provided you with some usable options, let us know what you finally decide as well as the outcome.

Have a good day,

Greg aka GW

bogstandard · 08-02-2008

Alan,
With regards to your 'dismal failure' scenario.
Rest assured, this is the way to go for just a couple of end flanges. Many thousands have been made that way, a few of them by myself.
All you have to remember is keep the metal soft, if you find it is starting to harden in any way at all, it needs annealing again. Four or five times is about the norm. It should bend and form just like lead sheet, with no 'Nora Batty' wrinkles.
The bit you have been forming will not be seen as it will be inside the boiler, so a few hammer marks won't matter.
If you want the flanged ends on the outside (like 'toy' boilers) then yes, you need to press or spin them to give you the nice edges.
If you are using standard plumbing pipe for your small boiler, then plumbers merchants should have pipe cappings pre-made, but I think they only mount on the outside and will need a bit of the flange removing as they are rather long. But I may be wrong on that score, you would need to check if they do internal ones as well.

As for pressing, speed and pressure is the order of the day. You have to get it done as fast as possible before the metal has time to work harden, otherwise you might find you will get half way thru the pressing and have to disassemble it to get the part out again to reanneal.

I hope that this hasn't put more confusion into the pot.

John

dipstick · 08-02-2008

i flanged the plates for my traction engine boiler by hand, so all i can say is just give it a go.

**Bunkerbarge** · 08-02-2008

Greg,

Just a point about silver soldering. I have done all my pipe fittings with silver solder and I always use a hand held blow torch for it. I think the key to success is a good hearth of a couple of bricks to maintain the heat in the area and whereas I agree an oxy-acetylene set would give you the required temperature in a much more controlled, smaller area, you can get by with cheaper, more readily available stuff.

alan2525 · 08-02-2008

I've got access to Oxy-Acetylene gear and also a Brazing Hearth at work.

I was going to silver solder the boiler ends and threaded bushes using the arcosa gas air torch at work. The Acetylene is at home, I've only used it to braze and weld mild steel.

I would have thought there was just too much heat and the heat was too localized that it would distort and even melt holes in the copper.

bogstandard · 09-02-2008

Alan,
A standard propane burner is all that is required.
Oxy/acet is just too harsh for silver soldering, it is ok for brazing with a carburising flame, but not for what you want.
Also remember that the flame should not go anywhere near the silver solder, heat up somewhere nearby and the solder will flow towards the heat. A good flux like Tenacity 4A will give you a good margin on heat range and ensure that you get good penetration.
When soldering in your bushes use either a graphite pencil or tipex (if you can find any) to draw a barrier line around the bushes, this will stop the silver solder from flooding over your boiler.

John

**GEEDUBBYA** · 09-02-2008

Howdy Alan,

Well, when i was building transformer parts, using alot of 1/2" dia. copper tubing for hook up leads, all we used was an acetylene torch and silver soldering rods.
I believe that everyone else may be thinking of a solder that is "pliable" and probably comes on a roll, what I was talking about and i apologize for not being more specific was silver brazing rods.....no flux (not even in the rods). And these rods do require an acetylene torch to melt them.
As for the issue of melting, like i said above, we used alot of 1/2" O.D. copper tubing and copper strapping and I can say I never unitntentionally melted any of them in the 20 yrs i worked there.
You can have the copper glowing cherry red long before it melts.

anyway, just wanted to clear up my earlier statements

have a good day,

Greg

alan2525 · 09-02-2008

I flanged the ends for the boiler, worked really nicely too! I was quite suprised! In the end I just turned a former to the inside diameter, allowing for the thickness of the copper sheet, and formed it in a vice with a ball pein hammer, using a propane torch to anneal a couple of times. Worked a treat! I skimmed a couple of thou off to get a nice fit in the boiler tube.