[metalmayhem]

I have read that IP67 means that it is resistant to being 1m deep underwater for 30 minutes.

Does it mean that the measuring performance is not affected by liquids? Because I would have thought that it would corrode if it was submerged in any liquid, especially coolant containing chlorine and sulfur.

If that was the case then the machines would be locked up with corrosion , theres not enough of those additives to cause severe damage if any damage at all . Stainless verniers are pretty durable measuring tools and they are something that a guy should only need to buy once or twice throughout a lifetime career . Because of price and longevity I have vernier for 18" and up , otherwise I find them a pita to read on a regular basis so I stick with dial for the most part and I also have a couple pairs of digital mitutoyo's .

as far as coolant proof digital go , mitutoyo , starrett , brown&sharp/tesa are good and they will stand up to shop challenges , there are also other quality brands . Everything else is pretty much junk especially any caliper coming out of china , I have yet to see a single pair come out of that country that can handle a few drops of coolant , or not be screwed within a couple months for other reasons . I bought a few pairs of igaging and thought they were pretty good until shortly after when they all stopped working in one way or another (mostly coolant related) . My digital mit's have never faltered and they look beat to snot after years of heavy use

The whole point of coolant proof calipers isn't to measure while submerged . It's so a machinist can measure in the machine and not have to worry about getting a drop of coolant on the scale . Our hands can become so saturated with coolant that the dampness and wet is enough to throw out normal calipers , even the quality calipers if they aren't coolant proof .
All of this is why I still lean towards dial calipers . As long as the gears are kept clean of fine chips then they last for years without issue