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- Feb 1, 2015
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The formula used in the three wire method is E = M-3W +.88803/n while the one used in the single wire method is E =2M2-M1 -3W +.86603/n.
If you can make a measurement within +/- .0001 of the true measurement and you assume a worst case erroro stacking the three wire method would give a maximum error of +/- .0004" while the single wire method would give a maximum error of +/- .0006". For most practical purposes they are equivalent. I have a set of PeeDee wires and FWIW, i miked them and found that they can vary from the nominal size by +/- .0001.
Weighing the slight decrease in potential accuracy against trying to balance three wires while making an accurate mike measurement, I believe that I will use the single wire method going forward.
I bought my set of wires from Enco just before they left the scene and they were quite reasonable. However, if a person didn't want to spring for a set of thread wires, I would suggest getting a set of 010" - .060" pin gages. They run about the same price as the thread wires but they have other uses in the machine shop
If you can make a measurement within +/- .0001 of the true measurement and you assume a worst case erroro stacking the three wire method would give a maximum error of +/- .0004" while the single wire method would give a maximum error of +/- .0006". For most practical purposes they are equivalent. I have a set of PeeDee wires and FWIW, i miked them and found that they can vary from the nominal size by +/- .0001.
Weighing the slight decrease in potential accuracy against trying to balance three wires while making an accurate mike measurement, I believe that I will use the single wire method going forward.
I bought my set of wires from Enco just before they left the scene and they were quite reasonable. However, if a person didn't want to spring for a set of thread wires, I would suggest getting a set of 010" - .060" pin gages. They run about the same price as the thread wires but they have other uses in the machine shop