Minimum bending radius

[Peter Simpson 3Participant @petersimpson3]

Hi does anybody know what the minimum bending radius for 6 mm OD x 1mm wall thickness Stainless steel tube ?

[Peter Simpson 3Participant @petersimpson3]

[Jan BParticipant @janb]

My RIDGID tube bender for 6mm tubes has a bending radius of 16 mm. The radius is measured to center of tube. When I make my own tube bender, I use a radius of 3x tube diameter and that works fine.

Jan

[Peter Simpson 3Participant @petersimpson3]

Cheers Jan. I was hoping for a a bit tighter radius. I will have to do some silver soldering.

[peak4Participant @peak4]

Just out of curiosity, as I didn't know the answer myself, I highlighted the relevant part of your question, and right clicked-search.
"minimum bending radius for 6 mm OD x 1mm wall thickness Stainless steel tube"

It took me straight here, to a pdf download which suggests 2x tube diameter.
https://www.listertube.com/links/tube-bending-design-guide/

Interesting document, overall, but see P14 to start

Bill

[Peter Simpson 3Participant @petersimpson3]

Hi Bill I eventually found that page myself. So minimum "U" bend would be 30 mm OD. Still too wide for superheat tubes as the Super heater flue tube is just less than 25mm diameter.

[DMBParticipant @dmb]

Peter, are you talking about the firebox end of the superheater? My commercially supplied stainless one has a large ish rad on both tubes which appear to have been welded to a spear point.

John

[Peter Simpson 3Participant @petersimpson3]

Hi John,

Thanks for the reply, My 5" gauge Don Young BR Standard 2 has 1" OD Super heater flue tubes. The super heater tubes are 7/32 OD. Looking at min radius of the tubes I will have to go for silver soldered copper or stainless steel spear head super heaters.. I have never silver soldered Stainless steel but using the correct flux should not be a problem. I have a Mig welder but would not be confident welding them.

[Martin ConnellyParticipant @martinconnelly55370]

The bend radius you can achieve depends on how you bend it, supported or unsupported internally, as well as wall thickness, outside diameter and material.

This was the cardboard computer I used at work to decide what tooling needed buying if a new part was designed outside of the existing product designs.

I can't find it at the moment but you can figure out from the pictures what would be possible for an unsupported bore. Beyond that there are a number of ways to support the internal bore to avoid wrinkling that have been covered in a number of threads.

Martin C

[Steve NeighbourParticipant @steveneighbour43428]

You can also use this formulae

Outer² – Ø / wall thickness = min bend radius

[duncan webster 1Participant @duncanwebster1]

Posted by Steve Neighbour on 26/12/2021 11:04:34:

…….

Outer² – Ø / wall thickness = min bend radius

Ø =?????

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Duncan, I take Outer² – Ø to mean outside diameter squared.

Regards Nick.

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