COPPER, which is one of the softest metals, is used to make tubing for many applications, such as refrigeration, laboratory, and processing. Soft metals are easier to bend than hard medals, but softness is a disadvantage when making a tight-radius bend. A soft metal can be especially troublesome when bending tubing smaller than 3/4 inch in diameter A tight-radius bend for copper is any bend with a radius equal to or less than approximately 2.5 times the tube's OD (that's 2.5D in tube fabricating jargon). The D of bend is the result of dividing the bend's centerline radius (CLR) by the tube's OD. For example, a bend with a 1.25-in. CLR on 1/2-in.-OD tubing equates to 2.5D of bend. A small CLR uses less material than a large CLR, and therefore is a big advantage concerning the cost of goods. So, when can you use a bend radius of 2D and when should you consider a larger radius? The answer lies, in part, in a tube characteristic known as the wall factor.
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