The value proposition for dial calipers isn't fantastic, because they're more susceptible to miscalibration and damage than digital or vernier models.
With a vernier, there's nothing to adjust; hopefully it's correct (you get good precision, but no control over accuracy). With a digital, if you screw up by touching the zero button, it's usually obvious that you need to recalibrate it (except with very thin features). However, you do need to be careful about where your zero is in the first place. But with dial calipers, if the dial shifts by half a degree, will you notice? (Note that this is independent of feature size.) You still have to be careful about your zero.
Besides, if you drop them, the dial sticks out and is relatively easy to break on a set of dial calipers. The LCDs on digital calipers don't like direct application of force, but are usually recessed and reasonably durable. Also, the racks and pinions inside of dial calipers are not particularly tolerant of grime (such as abrasive dust from grinding stones). This can lead to backlash problems, which make switching from inside to outside measurements a bit unintuitive. Vernier and digital calipers aren't immune, but their sliding ways are inherently smooth, and there's no backlash.
The nice thing about dial calipers is that you get a readout in thousandths of an inch, with some idea of ten-thousandths due to the position of the needle between the gradations. Of course, those ten-thousandths are pretty much meaningless unless you've got a top-quality instrument under controlled conditions. (In other words, not relevant to the typical FRC application.)
Ordinary digital calipers enforce the inherent uncertainty of the measurement by refusing to allow you to believe in any measurement more granular than 5 ten-thousandths of an inch. That could be good or bad depending on your perspective, but it's probably moot either way, for the same reasons that dial calipers aren't much use past thousandths.
In any event, if you do need ten-thousandths of an inch, a micrometer (and perhaps a set of expanding gauges) makes more sense, because of its inherent rigidity and (typically) finer scale.
Quote:
Originally Posted by DonRotolo
Using a good vernier caliper is a skill that will help you elsewhere in life.
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Other than facility with mental addition, what skill, useful elsewhere in life, do you learn by using vernier calipers, that you wouldn't also learn using dial or digital calipers?
Quote:
Originally Posted by squirrel
And they give good practice in your math skilz
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Doesn't that imply that if their math skills aren't up to par, they're more likely to introduce error into the measurement? (Not a problem with digital calipers.) In this regard, there's probably a (weak) correlation between good mental math skills, and a higher rate of parts that don't fit.