Bending brass angle into a circle.

[Raygers]

I have some 1/2" x 1/2" x 1/8" brass angle I need to bend into a 6" circle, it will be silver soldered at the join. I have tried bending it around a form without much success It twists and the worst part is that the 90 degree angle decreases by several degrees, this is not good for what I need.
Does anyone have tips or ideas for me? Even if I could anneal it, I don't have a suitable amount of heat to do that, I think that the 90 degree angle will change.
I don't have the resources to build a roller which may or may not work.

Any ideas would be very appreciated.
Ray

 

[Jasonb]

Faced with needing similar shapes in the past I have resorted to fabrication, cut an oversize disc, roll or bend flat stock into a circle. Lay circle onto disc and silver solder the two together. Then tidy up the disc to size

At that diameter with 1/2" leg even rolling will be difficult as there is a lot of metal that needs shrinking and extruded angle usually comes in one of the harder brasses that don't bend well

 

[Raygers]

Faced with needing similar shapes in the past I have resorted to fabrication, cut an oversize disc, roll or bend flat stock into a circle. Lay circle onto disc and silver solder the two together. Then tidy up the disc to size

At that diameter with 1/2" leg even rolling will be difficult as there is a lot of metal that needs shrinking and extruded angle usually comes in one of the harder brasses that don't bend well

Thanks Jasonb: that's what I was thinking.

 

[larryg]

Have you considered taking a solid circle ~8" in dia and sandwiching it between two 6" dia plates and hammer forming the lip around the plates? or roll forming it if you have a lathe. What properties of the finished product are important; size, thickness, material, structural, or cosmetic?

lg
no neat sig line

 

[kiwi2]

Hi Ray,
Not sure if this would work but might be worth a try.
Step 1. Put a saw cut through one side of the angle until it reaches the flat of the other side. Repeat this 20X? (might need more) at regular intervals along the length which will give a diameter of 6".
Step 2. Bend alternate tabs up by say 15 degrees. Bend the other tabs down by the same amount.
Step 3. Anneal the brass by heating to a red heat and let cool.
Step 4. Prepare a wooden former of the correct inside diameter (6"?)
Step 5. Bend the uncut part of the angle around the former by hand and silver solder the ends to produce a 6" cylinder.
Step 6. Bend the tabs towards each other until they are touching.
Step 7. Using a very fine blade (jewellers piercing saw?) cut through the tabs and discard the overlaps.
Step 8. Hammer the flange onto the former until the tabs all line up.
Step 9. Solder the cut edges of the tabs together.
Step 10. Put in the lathe and tidy up the face of the flange.

Then, if your lucky, Bob's your Aunty.

Regards,
Alan C.

 

[Raygers]

Thanks, everyone some good ideas here. Just to clarify, the vertical lip will be on the inside. I'm putting this on the back burner for the Christmas period, I'll get back to it in the new year.
Merry Christmas.

Ray

 

[djc]

If the vertical leg is on the inside, it is much easier to do what you want.

Anneal the piece and go around it with a cross pein hammer, concentrating more on the outside of the bend.

This will reduce the 1/8" thickness a little and cause the piece to curve. I think you can work out that a thickness reduction of 0.013" at the outside of the curve will give a 3 1/2" radius to the curve.

Like this, but by hand:



More generally, look at shrinking and stretching in the context of automobile body work. Shrinking is used much more in this area because the metal is already very thin (and will tear when stretched), but stretching is not unknown. You are starting with much thicker material, so stretching is a much less traumatic process.

Edit: see below for a simple tool that can be made. Make a mock up of the finished item in cardboard to determine the spacing of the two slotted bars of the tool that hold the vertical leg of the angle. In addition, make the two washers that are either side of the bearings much larger diameter and much thicker. Then they will guide the vertical leg of the angle being bent and prevent its natural tendency to move sideways (bend out of plane).

 

[Steamchick]

Anneal, - bend -Anneal - bend repeat... Many times!
K2

 

[Jasonb]

How important is the 1/8" thickness of the flat leg? at 6" diameter you are going to have to stretch the outer part of the leg a lot which will reduce it's thickness to about 80% or 0.0100" from 0.0125" and leave the leg tapered.

Don't think I would want to try and spin it in the lathe. I have spun items before but at 1/8" think it will not be easy even with a soft grade of brass.

Not the best photo but the two pieces of angle arrowed were formed as I suggested earlier, just the one heat to solder and both legs are a constant thickness and a true 90deg.

 

[Jasonb]

These Tee section rings are really no different to an angle section, just solder the "washer" to one end of the "tube" not in the middle. These are 6" dia x 1/8" again uniform thickness and all at right angles.

 

[Steamchick]

I was thinking a fabrication would be easier than bending angle if that size, without a proper industrial bender with appropriate tools/rolls.
Whereas making a ring of flat brass, and "washer" and joining with silver solder should be easier...
K2

 

[djc]

These are more questions than statements.

If this is for a model of a full size item, the full size item would have been rolled rather than fabricated, so any reduction in thickness of the horizontal leg is closer to reality. What is the balance between ease-of-manufacture and fidelity?

Also, the 1/2" x 1/2" x 1/8" dimensions of the angle seem a bit strange - the 1/8" thickness is 25% of the overall width. You cannot buy 2" x 2" x 1/2" angle iron. Do these proportionality issues cancel out at smaller scales?

 

[Jasonb]

Could be he is trying to replicate a cast part, I do it all the time where you use sheet, plate or bar to build up what would have originally been a casting.

 

[abby]

If I was making this part the obvious way would be to cast it , I did this for my Burrell traction engine front wheel rims of a very similar size , but then not everyone has foundry facilities.
Next best then would be to roll it , the" Angle Ring Co Ltd" in Tipton UK bend any section into circles and even spirals no job too small , but if you are not in the UK that's not much help.
I think many of us have made small tube benders , a small mill to roll this section shouldn't be too difficult to make and could be fun.
As the web is internal you could saw pieces out and simply bend around a 6" round bar end then silver braze the cuts, but it wouldn't give a perfect inner circle without a skim in the lathe.
If non of the above appeal then fabrication seems the only alternative.
Dan.