How much wire is needed to form larger loops?

Estimate wire length for larger loops

If the wire is wrapped tight around a circular mandrel shaped tool to make the loop, the best wire length estimate should be one revolution around the tool (d+t)𝝅, where d is the tool diameter and t is the wire thickness. However, often the wire tends to spring back and uncoil slightly which could affect the wire length needed. This experiment attempts to measure that tendency and identify how to compensate for it by adding padding p to the wire length estimate (d+t+p)𝝅. The wire length used for tight and loose loops with different wire gauge and large looper sizes are compared. Padding p = 0.1 mm was found to be sufficient for tight loops or loops with diameter 10 mm or less.

Wrap a piece of wire completely around a circular mandrel or looper tool and use a pen to mark across both wires while the wire is wrapped tight.

Release your grip and let the wire spring back if it wants to. You can see this happen as the two pen marks that were aligned before spring apart a short distance.

Make a new mark that is aligned. When you straighten the wire, measure the distance between marks as wire length used for tight and loose loops.

The (d+t)𝝅 estimate will be quite sensitive to tool diameter so you need to carefully measure the tools with a caliper. I found that I couldn't get a consistent measurement with some of the tools because they were slightly oval shaped rather than perfectly circular. So I rotated the caliper around the circle, measured the smallest and largest diameter, and averaged them to get d. Subtract the (d+t)𝝅 estimate from each wire measurement to get a wire length error. Divide wire length error by 𝝅 to get loop diameter error shown in the chart below.

Notice how the loop diameter error for tight loops is consistently small (but still positive) across varying wire gauges and tools. So even if you are making tight loops and keeping them secured somehow, adding a small amount (p = 0.1 mm) of padding with (d+t+p)𝝅 is not a bad idea. Not only is there more error with loose loops as expected, but the error tends to increase with increasing tool diameter and wire gauge.

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