I have stopped using or trusting the cc-2. I seemed to be going through chains really quickly and I checked a brand new chain. That chain showed nearly .5 on the tool so I checked a few at the shop and theirs read the same. Not sure why but the 3.2 seems to be much better even if it is a go, no-go style.
Problem with the C-2 is that if just once, you put more than super light pressure on the thumb lever it will bend the pin and you have ruined the measurement capability from then on. First person you lend it to who does not know how to use it will take care of that for you.
From Sheldon Brown (RIP):
Measuring Chain Wear The standard way to measure chain wear is with a ruler or steel tape measure. This can be done without removing the chain from the bicycle. The normal technique is to measure a one-foot length, placing an inch mark of the ruler at the side of one rivet, then looking at the corresponding rivet 12 complete links away. On a new, unworn chain, this rivet will also line up exactly with an inch mark. With a worn chain, the rivet will be past the inch mark.
This gives a direct measurement of the wear to the chain, and an indirect measurement of the wear to the sprockets. first, let’s look at how to do this with a ruler that measures in inches.
If the rivet is less than 1/16" past the mark, all is well.If the rivet is 1/16" past the mark, you should replace the chain, but the sprockets are probably undamaged.If the rivet is 1/8" past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.If the rivet is past the 1/8" mark, a new chain will almost certainly skip on the worn sprockets, especially the smaller ones.
In metric measurement, 10 links of a new chain are 25.4 cm, or 15 links, 38.1 cm.
If the rivet is up to 25.5 cm or halfway between 38.2 cm and 38.3 cm, all is well.If the rivet is a little bit past 25.5 cm, or approaching 38.3 cm, you should replace the chain, but the sprockets are probably undamaged.If the rivet is approaching 25.7 cm or 38.5 cm, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at this point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.More than that, and a new chain will almost certainly skip on the worn sprockets, especially the smaller ones.
There are also special tools made to measure chain wear; these are a bit more convenient, though by no means necessary, and most – except for the Shimano TL-CN40 and TL-CN41 – are inaccurate because they allow roller play to confound the measurement of rivet-pin wear.