Originally Posted by
RandomTroll
I have a good-quality metal ruler. I have a hard time measuring chain stretch with the necessary precision (I discard at .5% stretch.) when mounted. And I have no chance of measuring it to ,03mm precision. The extra precision of the digital caliper makes it superior. Plus it applies stretch itself as well as anchors itself between the points it measures. But, obviously, I have been careless about placing its jaws in the same place on the pins.
Interesting that you work with
percent of length as a measure of stretch, or did you mean .5 mm?
Most people use inches, and discard a chain when it stretches beyond 1/16 inch over a 12" span.
So you use the "inside" caliper jaws to pull the rollers apart? Good thought, but with the right pedal at 3 o'clock and a sneaker hanging off it, you have a straight-enough chain.
I prefer the ruler because it measures a larger sample of the chain and shows stretch as a percentage of 12 inches rather than of just a few links. Your method seems to be drawing you into issues, like pin diameter, which are irrelevant if you measure a larger number of links.