That's correct!
I forgot about adding the notch though in my earlier post. What I done for this
was where the bend started and stopped, generally where two bend lines meet, is
drill a 1/8" dia hole at the intersection before cutting out the notch. You'll
notice this on a bunch of chassis however it's been punched. Some corner
notcher punch/dies have this built in. For 1/16" thick material, about 14 gage,
you use a 1/8" radius bend or X 2 the material thickness as he said. Sharp 90
deg bends are best done on soft, thin material, and steel holds up better than
aluminum doing this. However in steel, you would use about 20 gage.
Best,
Will
*********** REPLY SEPARATOR ***********
On 8/5/05 at 3:48 AM N7KA@comcast.net wrote:
>Forming of a metal such as aluminum depend on the temper and thickness of
>the material. There is also the issue (for very tight bends) whether the
>bend is across or a parallel to the grain of gthe material (across the
>grain is best). This can not be controlled to a large degree when making
>a box from a single piece of metal. The ASTM and previous mil specs
>stated a minimum radius of a bend for the different tempers and thickness
>of the material. It varies , however, a safe "rule-of-thumb" is 2 times
>the material thickness. I have seen material fracture explosively when
>bent to tight for the temper and thickness. Our worse case was material
>purchased during a strike at an aluminum manufacturer and replacement
>workers (from the office ranks) lost the recipe and the material was not
>of correct composition or temper.
>
>A very loud BANG could be heard in nearby offices and there was a rush of
>folks to see if any one was injured (fortunately not). Many of us
>recognized the bang as a major safety problem and use of the material was
>halted immediately. Took several months to get replacement material. The
>mfr was removed from source of supply for extended time and a lot of
>qualification efforts followed prior to re-instatement.
>
>Bud chassis were made from a soft aluminum (think 5052 temper or softer).
>Anything above 6061 is quite brittle.
>
>A radius (notch) at the point of bend and edge of the material helps to
>reduce cracking at the edge. Many programs for punching out a flat
>pattern (calculated size for material to make a finished part) include a
>round notch at point of the bend and edge of material (especially at a box
>corner bend.
>
>Hope this helps.
>
>73 de Arne N7KA
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