The Home Machinist!

I've read here a number of times how expanded in-place copper tubes in a steel boiler move over time. What are people's opinions on slightly flaring the protruding tube ends after expanding to stop or slow the movement?
Edit: This is my second boiler build, my first was welded copper with silver soldered tubes. Expansion and contraction of the tubes wasn't a concern.
Denny

My understanding is that, when the tubes are properly rolled with a tube roller, they are slightly expanded on both the inside and outside of the tube sheet thereby locking them in place.

I don't think it's worth it. In fact, I don't see how flaring the end will keep the tube from growing. I have tried several ways of fastening tubes - silver soldering, swedging, urethane expanders. I now use a commercial roller with lubricant and leave them as rolled. I roll them as lightly as I can to get them to seal. I do not anneal the tube beforehand. I'd rather go back and re-roll a weeping tube rather than over-roll.
The growth I've noticed doesn't seem to hurt anything.

No....flaring will not have any effect on this.

At best, flaring will improve the flow

just learning how to roll tubes - you don't anneal first? Just got a tube roller

Some do, some do not.

As soon as you start to roll, the annealing is out the window anyway

Some say that it helps to keep from cracking tubes

Bill Shields wrote: ↑Sat Feb 11, 2023 4:42 pm Some do, some do not.

As soon as you start to roll, the annealing is out the window anyway

Some say that it helps to keep from cracking tubes

I found it easier to roll after annealing.

But I also know I reduced the coppers strength by 10x (apparently 600psi crush pressure vs 6k) if data material sheets are to be believed.

There shouldn’t be problems with cracking, unless the tubes are over-rolled, which reduces their thickness. I followed Marty’s recommendation of making the holes in the rear tube sheet the same size as the o.d. of the copper tubes, and the front sheet 0.005” oversize. Tubes were not annealed before rolling. After rolling, none leaked.
Incidentally, I have seen tubes that began to leak “heal themselves” without needing to be re-rolled. Evidently, the leak between the copper tube and the steel tube sheet became filled with rust after a few months.

Absolutely true on what fender said - been there done that.

FWIW:

a seriously under rolled tube will leak like a geyser and generally require rework.

after rolling, I generally put a couple of psi air in the unit and soap it with a brush.

Not to hijack this thread but what manufacturer tube roller is best to roll copper in a steel boiler. I am going to need one and request recommendations.

Lest cost

I use Wilson and / or Elliott -> but hang on to $$

There are many manufacturers, but if you are in the boiler or hex business, there are the GOTO companies, and have been for decades.

You first need to know tube dimensions as well as clearance to closest obstruction.

What is the center distance from any tube to the closest anything that can get in the way of inserting the roller.

Generally the smokebox end is not as much trouble as the firebox end

Something to consider if space is tight.
Pictured below is my commercial roller and my homemade roller, both fit 1/2" K copper tubing.
The home built roller doesn't have many clearance problems. They seem to work equally well.