Arcs for bending on edge

[mkr5000]

Let's see if I can explain this --

I'm doing a drawing for an aluminum chassis and I want a 90 degree
bend exactly on the edge of the material. (062 aluminum)

Now, the way it's supposed to be done is that you cut/punch a couple
of arcs on each side of the bend, right?

Here's my question:

What are the guidelines for sizing these arcs? For example, should
the arc radius be 3-4 times the size of the material thickness?
(more? less?)

Say, the "O" is actually an arc (half circle) and the bend is between
the 2 "O's"

--------------O----------------------O---------------

 

[JeffM]

(Posted to rec.crafts.metalworking, sci.electronics.cad)

I'm doing a drawing for an aluminum chassis

Which Electronics CAD program are you using to do this?

http://groups.google.com/groups/search?q=ingroup:cad+-electronics

 

[Jim Wilkins]

I'm doing a drawing for an aluminum chassis and I want a 90 degree
bend exactly on the edge of the material. (062 aluminum)

Now, the way it's supposed to be done is that you cut/punch a couple
of arcs on each side of the bend, right?

Here's my question:

What are the guidelines for sizing these arcs? For example, should
the arc radius be 3-4 times the size of the material thickness?
(more? less?)

Say, the "O" is actually an arc (half circle) and the bend is between
the 2 "O's"

--------------O----------------------O---------------

1/8" works. Try it on some scrap first. If it's 6061 T6 you may need
to pad the inside edge with flashing etc to increase the bend radius
to keep the outside from cracking.

Or ask the shop that's going to fabricate it.

 

[mkr5000]

So just think in terms of .125 (radius) for all material or do you
mean .125 for .062 aluminum?

I can't imagine ever using anything thicker than 062 so I'll make
mine .125 as you suggest.

That's good because the smaller, the better.

Thanks for the feedback.