Spring index
Category: Dimensions & geometry
The ratio of the mean diameter to the wire diameter (C = Dm / d), indicating how “tight” or “open” the spring is.
Values between 4.5 and 12 are ideal for manufacturing. Very low indices create high stresses and coiling difficulty; very high indices make the spring fragile and prone to tangling. Outside 4.5–25 the spring is usually not manufacturable.
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