Originally Posted by
KerryIrons
Stop confusing yourself and measure with a ruler. You can see if the ruler measurement is different when the quick link is in the measured segment. Chain should show no more than 1/16" elongation in 12" of original length. Chain checkers have a questionable reputation for accuracy, which should surprise no one since they are measuring over such a short section of chain.
Using a ruler is out of question. I don't care for the exact stretch. I prefer other means that quickly show you it is time for a chain to leave the floor. Chain checkers are pretty accurate. There is also a
nice test for the accuracy of some of them.
Just for the history, I eventually found out that you do not measure over the quick link. The pins of the quick link are grooved so that the interlock with the sockets in their plates. The total difference in length can be of 1mm or more and hence the discrepancy when using a chain checker over them.
As all others said, I shouldn't do this over the quick link.