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Old 01-13-2012, 11:35 PM
Bricktopp Bricktopp is offline
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Default Against the grain or with it?

I know we make all types of shapes with metal but in the case of say a simple radius bend is it better to go with the grain or against the sheets grain? Any pros or cons? Or indifferent. Ive made hundreds of bends and never gave it any thought till today.

D
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Old 01-14-2012, 11:03 AM
cameron cameron is offline
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You can make a bend with a tighter inside radius without cracking if the bend line is across the grain, rather than parallel. For ordinary work, it's usually good practise to use an inside radius large enough that you don't need to be unduly concerned about grain direction.

Dave Cameron
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Old 01-14-2012, 11:06 AM
Johnny C. Johnny C. is offline
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Hey Guys, What do you think happens when you mix grain directions in a panel made of several peices?
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Old 01-14-2012, 05:43 PM
cameron cameron is offline
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Common sense might suggest that some of the bends will be along the grain, and some across. Hence my suggestion of using a large enough radius that you don't have to be concerned about grain.

What do you think happens ?
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Old 01-14-2012, 07:56 PM
peter d peter d is offline
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Default grain

Hi I have never heard of a grain in metal and certainly have never seen one. how do you see it or work out which way it is flowing for want of a better word.
thanks peter
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Old 01-14-2012, 08:32 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by Bricktopp View Post
I know we make all types of shapes with metal but in the case of say a simple radius bend is it better to go with the grain or against the sheets grain? Any pros or cons? Or indifferent. Ive made hundreds of bends and never gave it any thought till today.

D
When you bend with the grain the bend is easier to make and the resultant part is fairly strong. When you bend across the grain the bend is more difficult to make, but the resultant part is stronger. Bending with the grain has a risk, however, as bending too tightly can cause the grain to open into cracks on the back side of the bend. This is why, in aircraft work, the hard aluminum alloys have prescribed bend radii, making for gradual bends that do not stress the grain to the point of causing fracture over time.
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Old 01-15-2012, 10:43 AM
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rlile rlile is offline
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Typically the grain runs the direction of the long side on a sheet (mill rolling direction)
Sometimes its easy to pick up.... Its goes with the "scratches" in a fresh sheet.
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Old 01-15-2012, 01:17 PM
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Originally Posted by rlile View Post
Typically the grain runs the direction of the long side on a sheet (mill rolling direction)
Sometimes its easy to pick up.... Its goes with the "scratches" in a fresh sheet.
Yes, since the rolling mill makes the grain directionally parallel to the run of the product. Seeing it on a 2B finish can be difficult, for instance. And - if you are unlucky enough to only have a pre-cut sheet that is 4'X4' or such, finding the grain can be difficult if the surface has already been polished (2B) out. In that case sometimes it is best to magnify the edge for the factory cut, in order to find the grain direction, again.
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Old 01-15-2012, 08:48 PM
Bricktopp Bricktopp is offline
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Thankyou for your replies. Another question. Does it matter more with say the higher alloys used for planes over say a 3000 series aluminum where its application is less critical?
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Old 01-15-2012, 08:59 PM
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Joe Hartson Joe Hartson is offline
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There are several thing that have to be know to answer the original question. The bend radius is alloy specific and thickness related. 1100 and 3000 series are the most forgiving and can accept a tight radius.

You can tell the rolling direction on all aluminum sheet except bright sheet that is rolled with mirror finished rolls. The scratch pattern on the rolls will imprint on the sheet as it is rolled. Look for the long line pattern on the sheet and that is the rolling direction. Look at the bottom of an aluminum drink can and you will see a pattern and can tell the direction of rolling. People that are really familiar with can stock can you what plant rolled can stock based on the scratch pattern on the aluminum sheet. The edges of the sheet are cut with rotating slitter knives and the ends of the sheet are cut with a shear most of the time, there are exceptions on the end cuts. Material that is sold in a roll form has not been flattened and therefore has some stresses built into the sheet that the flattened product don't have. Knowing the complete designation of the alloy will help in understanding what you can do with the sheet.

Here is a link that will help with the number designation on the sheet products.
http://www.alcotec.com/us/en/solutio...ion-System.cfm
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