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Rolling Thin Wall Brass Tube

jwhartley

Plastic
Joined
Oct 20, 2004
Location
Minnesota, USA
As has been mentioned, musical instrument have many bends that are similar, conceptually, to what the OP is trying do do.

The best example I can think of is the bell-tail on a trumpet. The tubing is ~0.6" in diameter and the 180deg. bend has a diameter of ~4-5". The wall is something like 0.030".

You can see an example of making the bend here: YouTube
See time: 5:10
This is the Yamaha procedure. You can see that they are using Cerrobend or some similar low-temp alloy to make the bend. I have seen other manufacturers use water, then freezing to support the tubing for the bend. They add a little detergent to the water to make the ice weaker and less brittle. The water is a lot easier to clean up than the Cerrobend.

My experience with instrument tubing suggest that annealing the tubing beforehand would be a good path to success.

When making the bends, you still can get some wrinkling. These are then hammered out to smooth up the bend.

-Jess
 

dsergison

Diamond
Joined
Oct 23, 2003
Location
East Peoria, IL, USA
As has been mentioned, musical instrument have many bends that are similar, conceptually, to what the OP is trying do do.

The best example I can think of is the bell-tail on a trumpet. The tubing is ~0.6" in diameter and the 180deg. bend has a diameter of ~4-5". The wall is something like 0.030".

You can see an example of making the bend here: YouTube
See time: 5:10
This is the Yamaha procedure. You can see that they are using Cerrobend or some similar low-temp alloy to make the bend. I have seen other manufacturers use water, then freezing to support the tubing for the bend. They add a little detergent to the water to make the ice weaker and less brittle. The water is a lot easier to clean up than the Cerrobend.

My experience with instrument tubing suggest that annealing the tubing beforehand would be a good path to success.

When making the bends, you still can get some wrinkling. These are then hammered out to smooth up the bend.

-Jess

what a fantastic factory tour!
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
I watched plenty of tube bending videos on youtube. Not the garage shop kind but the ones with automated machines rolling stainless tubing.
Never was there one mention of using sand or frozen water. I was impressed and contacted a professional business that wanted to get a drawing
with dimensions, etc. Probably would have cost several hundred but I'm not sure. The tightest radius they could do was something like a couple
of inches with 7/8" OD copper.

Using ice the bend has to be worked quickly as the ice melts. The water turns to ice and expands so a small air gap should
be allowed for before sealing the ends. Cannot do anything too large unless there is a walk-in freezer. Burrr.
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
You can see an example of making the bend here: YouTube
See time: 5:10
This is the Yamaha procedure. You can see that they are using Cerrobend or some similar low-temp alloy to make the bend. I have seen other manufacturers use water, then freezing to support the tubing for the bend. They add a little detergent to the water to make the ice weaker and less brittle. The water is a lot easier to clean up than the Cerrobend.

Cool video. I picked up a fact or myth about adding a little soap. The soap is used as a lubricant inside the tube as it moves in the bend process.
 

Newman109

Diamond
Joined
Sep 4, 2006
Location
Sacramento County, California, USA California
I watched plenty of tube bending videos on youtube. Not the garage shop kind but the ones with automated machines rolling stainless tubing.
Never was there one mention of using sand or frozen water. I was impressed and contacted a professional business that wanted to get a drawing
with dimensions, etc. Probably would have cost several hundred but I'm not sure. The tightest radius they could do was something like a couple
of inches with 7/8" OD copper.

Using ice the bend has to be worked quickly as the ice melts. The water turns to ice and expands so a small air gap should
be allowed for before sealing the ends. Cannot do anything too large unless there is a walk-in freezer. Burrr.

Use key words "using sand to bend tubing".

YouTube

Use key words "using ice to bend tubing".

YouTube
 

kenton

Hot Rolled
Joined
Dec 15, 2015
Using ice the bend has to be worked quickly as the ice melts. The water turns to ice and expands so a small air gap should
be allowed for before sealing the ends. Cannot do anything too large unless there is a walk-in freezer. Burrr.

Move north and do your bends outdoors between November and February.
 
Joined
Jan 22, 2019
As has been mentioned, musical instrument have many bends that are similar, conceptually, to what the OP is trying do do.

The best example I can think of is the bell-tail on a trumpet. The tubing is ~0.6" in diameter and the 180deg. bend has a diameter of ~4-5". The wall is something like 0.030".

You can see an example of making the bend here: YouTube
See time: 5:10
This is the Yamaha procedure. You can see that they are using Cerrobend or some similar low-temp alloy to make the bend. I have seen other manufacturers use water, then freezing to support the tubing for the bend. They add a little detergent to the water to make the ice weaker and less brittle. The water is a lot easier to clean up than the Cerrobend.

My experience with instrument tubing suggest that annealing the tubing beforehand would be a good path to success.

When making the bends, you still can get some wrinkling. These are then hammered out to smooth up the bend.

-Jess

Thanks Jess. The soap and frozen water sounds like a promising lead, as I don't have nearly enough cerrobend (or Wood's metal) to fill the tube.

Thanks all for the input.
 

Onepass

Hot Rolled
Joined
Jun 2, 2014
Location
Kansas City
I used to work at a shop that had several regular jobs bending stainless steel thin wall tube in different configurations and diameters, the largest diameter was about 1 1/4”, I think. We used a pressed in aluminum mandrel or a UHMW mandrel that was several thousandths over size and frozen in dry ice for awhile to shrink. After bending in very close fitting dies in a press, the aluminum and UHMW was melted out. Freezing water in the tube with a washer welded on the ends to contain the water, only worked on the easiest bends- I don’t have much hope that the tight bend you are talking about will work

If you were to put some kind of a stopper it the tube that is downstream from where your bend is - that way you wouldn’t need as much low temperature metal and you could melt it back out. Or use the UHMW ( I don’t remember how much the size difference is, but you could freeze a piece and see how much it shrinks- and just leave it in. Same with the aluminum, although it might be a little heavier.
 

Whetstone

Cast Iron
Joined
Mar 27, 2011
Location
Providence RI
I have a fair about of experience with bending brass and you definitely need to anneal the tubing. Checking this mandrel chart you definitely need a mandrel bender and wiper to make your bend without failure. Can you up the wall thickness to 1/4"? Im local and can help you mandrel bend 1.5" tubing, but not 2".
 

memphisjed

Stainless
Joined
Jan 21, 2019
Location
Memphis
Your pressure/counter die does not have required pressure (to much gap) on tangent edge. Not sure where the adjustment is on the JD, sorry. Also, high pressure grease the counter die beyond necessary, the brass is will want to guall if it catches an edge on the infeed edge.
If brass is sticking at all to counter die it is stretching, reducing pressure at tangent.
I open bend a fair amount of pipe, and you are pushing the limits of wall thickness without going to a mandrel or crazy linear railed counter die - but doable. Your radius after bending should be 3 5/8 on pipe if all tooling is dialed in to right (1.03 (magic bend constant) x 3.5 (die radius)).
 








 
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