All About Chain Types
In North America, five types of chain make up the bulk of all chain types used for anchoring. Here are the differences between them:
| G30 - Proof Coil | A general purpose chain of normal commercial quality. Constructed from low carbon steel. Proof coil chain doesn't have a uniform pitch and does not work with windlasses. It is hallmarked approximately every foot with the manufacturer's symbol and grade marking: 3, 30 or 300 |
| BBB Anchor/Windlass Chain | A short link chain of normal commercial quality. Constructed from low carbon steel. It has a uniform pitch short link and works well with gypsies. It used to be the standard for windlasses but it has largely been replaced by G4 Chain. It is hallmarked approximately every foot with the manufacturer's symbol and grade marking: 3B |
| G4, G40, G43 -High Test | This is the standard for most windlasses today. Made from high carbon steel, it has twice the working load of BBB chain which allows a smaller chain size to be used. It is marked approximately every foot with the manufacturer's symbol and grade marking: G4, G40, G43 or G400. |
| G70 - Transport | This chain is commonly called G7 or transport chain. It has a very high strength-to-weight ratio and it has about 25% more strength than high test chains. It works with very few windlasses however. It is hallmarked approximately every foot with the manufacturer's symbol and grade marking: 7, 70, 700. |
Other points to consider:
If you're using a windlass, choose your anchor chain according to the manufacturer's specifications
Generally the higher the grade, the higher the holding power, and the heavier the chain
If you're using a chain and rope setup with your windlass, the chain will need to be spliced to the rope
Stainless steel chain is less prone to rusting (and looks a lot better!) but it has a lower breaking point than galvanized chain
What the chain grades mean?
This is irrelevant to almost all, but for the bookworm, chain grade numbers are actually expressed in 1/10ths of the actual grade. For example, grade 40 is actually grade 400. The grade represents the tensile strength of the chain. To calculate the tensile strength you multiply the grade times the area of the two cross sections of a link (which involves a particularly nasty math formula).