Measuring the chain link size of a marine anchor chain is vital for ensuring proper compatibility with anchor windlasses and our anchor chain markers, as well as for assessing the chain's overall strength and durability.
It's important when determining what chain size you need to replace existing chain for your boat, especially if you use a windlass to launch and retrieve your anchor.
Here's a step-by-step guide to accurately measure the chain link size:
Use a suitable tool for measuring: For accurate measurements make sure you use a set of callipers or vernier. These tools allow you to measure the diameter of the chain link accurately. You can use a ruler or tape measure but the end result will be less accurate.
Refer to Standard Units: Chain link sizes are typically measured in millimeters throughout the majority of the world or inches typically in the US. Ensure your measurements are recorded in the appropriate unit of measurement for consistency and compatibility with industry standards when talking to manufacturers, although most will be able to convert across quite easily.
Take Multiple Measurements: To account for any slight variations, measure multiple links and take an average to obtain the most accurate result.
Now on to the actual measuring...
Wire diameter (wd) - The wire diameter is the diameter of the metal which forms the chain link. This is the measurement used when referring to your chain size, so it is an important measurement to know. A 12mm anchor chain will have a wire diameter of 12mm.
Position the calliper or gauge around a part of the chain link on the side which does not have the welded join. Take care to ensure that the tool is perpendicular to the link to obtain an accurate reading.
Pitch (il) - this is the internal length (marked as "il" ) of the chain link and is important for correct alignment with your Gypsy / Wildcat when using a windlass. If the pitch of your chain does not match your gypsy / windlass properly the chain will jump or jam in the windlass.
Backup method: If you do not have callipers there is a more complicated backup method for getting an accurate measurement below, but use this as a last resort.
- Select a suitable short length: Choose a typical length from the anchor chain for measurement. Ensure it's none of the links are deformed or damaged and the chain is relatively clean, as this could affect the accuracy of the measurement.
- Measure 10 full links when the chain is pulled tight - record this down (L)
- Measure the chain wire diameter as above (wd) and multiply this by 9
- Add the two together
- Divide this number by 10
- Subtract the wire diameter (wd)
Pitch = ((L+(9 x wd))/10)-wd
Inner width (iw) - This is important for us manufacturing the anchor chain markers as it determines how wide the markers need to be to fir in the link comfortably and not fall back out.
Inner width joint (iwj) - Due to the metal diameter at the joint being slightly wider we make an allowance for this, but it is important to know that measuring the chain here will give a different measurement of the chain link. Measuring here will not give an accurate measurement of the wire diameter, ie the chain size.
Regular inspections and keeping a record of these measurements are essential for maintaining the reliability and effectiveness of your anchoring gear, contributing to your overall safety and security. If you can keep a record of these measurements and check them on an annual basis you will be able to see if you chain has stretched over time, in which case it should be replaced as the links will have weakened and deformed slightly.
A last note about ISO / DIN standards
DIN and ISO standards dictate the maximum and minimum measurements of the chain link dimensions and for this reason not all "standard" chain is necessarily the same. For example DIN766 14mm chain can vary up to 4mm in link width meaning different Anchoright anchor chain markers may be required. If you are measuring up for a new chain it is good practice to double-check with the manufacturer what their ACTUAL chain link dimensions are to ensure the chain will fit in your machinery.