Bending Box Section

[Gasman]

I might have to do a job lot of bending of box section
I'm hoping that some of you may be able to suggest the best or quickest technique without having to source expensive kit.

It's for 25mm x 3mm box section and just a single neat 45 degree bend at one end of a 1.2m length. Simple enough but I don't want to distrort the material and there will be quite a few to make.

I thought of the hilmore type unit (used for conduit etc) but with square dies??

Thanks in anticipation.

 

[Hitch]

I recently did 45s in a cheapy clarke bender, using the standard tube dies

I will have a look for it...

Edit- pic added, it wasnt quite 45 looking at the pic, but hadnt started to distort at that angle.

Whats it for??

 

[busa]

I've also bent box section (40 x 40 ) using a staffa pipe bender although if I remember correctly it was only to about 30 degrees. I made a simple former using two cheek plates and a curved back plate out of 10mm with a short length of tube to slip over the bender ram. The set up worked well.
.

 

[scott0031]

Hi,

Its pretty easy to make something up if you have access to a lathe, the rest of the parts for a simple bender can be pretty rough and ready. The only important bit really get constancy is a decent fitting and size pin in the former and a decent end stop that you can adjust to suit, so you can form the bend where you want it repeatably. Formers for box are very easy to make in comparison to rigging up to do round tube.


In essence as 'busa' mentioned you can use a bit of round bar with a hole in the middle(where the location pin goes) and then add cheek plates to encapsulate the walls of the box. This will, as with all formers help eliminate the distorting associated with trying to compress and stretch a material at the same time. The bigger the bend rad the better, as this gives more space for the material to shrink and stretch. the tighter the rad gets the more tricky it gets. So lets say you have 1' sq box and you want say 4 inch inside rad (that's not centre line, for ease of explaining) you will need a 4' inch diam bar and 2 off 6' cheek plates,(that give you the depth you need ie 6-4 = 2 but that 2 is then divided 2 again as its a diameter and that's 1' per side.) they can be fully round plates or you can make only1 plate and split off the section you need to cover the angle you are trying to achieve. It sometimes best to make the cheek plates a bit deeper than required so lets say an instead of 1' deep you could make it so its 1 1/8 deep this gives u more scope to stop deformation of the tube as its deeper than required and stops material trying to squeeze out of the former area.

Its best to try to make a rotary draw type bender this means the tube is drawn around the former rather than being compressed around it as with a typical plumbers bender that has an external former as well as the internal former. So the tube is actually held in the former by a retaining mechanism of some kind, then the actual former is rotated, So when you rotate the former the tube goes with it. This method also requires a bit less force and produces a lot better results than the 2 former type typical bender used for plumbing etc.

If you have a lot of these to do and likely to be repeated its wort spending a few days knocking something up half decent. It will make life a lot faster and give repeatability to very good accuracy if the tooling is right.


Hope this is of some help.


Kind regards,

Scott (Ward eng)