Metal Bending

[dirtyhanfri]

Hi

I just bought this sheet bender for a few €'s

It's a DIY model made by someone, quite heavy and sturdy, If I sell it just by iron weight value I'll be making money on this...

I'm going to use it to bend 1,5 stainless steel to make enclosures.

I'm going to start with 500 modules enclosures and a little enclosure for a module tester, but I'm able to do even rack enclosures with this (blade is almost 580mm wide).

I have a pair of designs to start playing with it just to check final measurements after bending and such, but I have no experience on manual bending.

I think the trick here is the tooling, I'm thinking in get some steel blocks of different sizes and put them between the blade and the piece to be bent, that way I could get sharp 90º corners and clearance between the blade and previously bent lips (not sure if I'm explaining well here, my english is not so good)

Any experience on this? Any tip is apreciated...

Some pics of the machine:

The blade looks pretty good:

This looks well done:

It's hard to see here, but you can move the whole piece holding the blade some mm and adjust it with the allen screws, I think it's for different sheet depths (BTW the red in the allen screws is not rust, just red paint) Also you can see here the structure is a bit weird, looks like made from scraps, anyway it's functional:

 

[JohnRoberts]

We called this a "brake"... my advice is watch out for your fingers.

JR

 

[dirtyhanfri]

my advice is watch out for your fingers.

Nice tip!, Actually I love my hands with 5 full fingers each so I'll try to keep them that way. 

 

[JohnRoberts]

Welcome to the world of bend allowances. Metal doesn't bend perfectly with right angles, but there will generally be a small radius for even the sharp bends. So a sheet of metal with multiple bends will exhibit slight length variation.

Not a huge error for simple projects but indeed make a prototype first to get the fit perfect, or as close as you can.

JR 

 

[dirtyhanfri]

Yes, that's my main concern with it.

I've been reading about it, the main problem is I'm not sure how to measure corner radius accurately, all the calculations about how to get precise sheet length are based on that radius.

So I'll get some sheets and see how it works...

About tooling I think I will search for the solutions after seeing the problem.

 

[Gene Pink]

I've been reading about it, the main problem is I'm not sure how to measure corner radius accurately, all the calculations about how to get precise sheet length are based on that radius.

It has been decades, but I seem to remember a "one third" rule of thumb.

If you visualize a plane that is one third the depth into the sheet metal and calculate from that, it gets you fairly accurate.

I believe the idea is that when metal is bent, the inner third on the inside of the bend compresses, and the outer two-thirds stretch. And bend radius didn't really matter.

Just something from the cobwebs, so take this with a 50 Lb bag of rocksalt.

Gene

 

[JohnRoberts]

Life is short, we can bend up a prototype and figure out empirically what we need...

JR

 

[dirtyhanfri]

It has been decades, but I seem to remember a "one third" rule of thumb.

If you visualize a plane that is one third the depth into the sheet metal and calculate from that, it gets you fairly accurate.

I believe the idea is that when metal is bent, the inner third on the inside of the bend compresses, and the outer two-thirds stretch. And bend radius didn't really matter.

Just something from the cobwebs, so take this with a 50 Lb bag of rocksalt.

Gene

Thanks for the explanation. Afriend of mine said me something similar a few days ago, he was a bit more cryptic, just said "with two bends at 90° in a 1,5mm add 1mm to the length where the bents are and you'll be fine"

Life is short, we can bend up a prototype and figure out empirically what we need...

JR

Nice advice, time to get some aluminum sheets and start bending.  ;D

Thanks

 

[JTraverse]

Search for "bend allowance" calculations. It changes with thickness, angle and material. The radius is dependant on the dies used. At our shop we use Amada brakes with a selection of dies and punch attachments. For a DIY job like this, experimentation will probably be the best way.