Plastic “Vernier Calipers” are extremely cheap and while not the most accurate or durable of measuring devices are perfectly fine for many uses such as quickly measuring stuff up for your 3D printed designs.
But of course, you do have to know how to use one. This will take you about the next 30 or so seconds to learn.
The caliper pictured below is measuring roughly 12.5mm +/ 0.1mm
You can see that the first line on the lower scale is just after 12mm, so you know it’s more than 12mm, but how much more?
Each numbered line on the bottom scale is 0.1mm extra, each unnumbered line is 0.05mm extra.
The closest matching line is the amount to add.
Look along the scale until you find the first place where a numbered line on the bottom scale aligns to a line on the top scale.
Since the first (closest) matching line (to my eye) is numbered 5, the measurement is 12mm + 0.5mm, tada 12.5mm.
Of course, lines 4 and 6 are also pretty close, so let’s say it’s about 12.4mm to 12.6mm.
In theory you could look closer and see one of the unmarked lines either side of that 5 line is aligned better, for example you might decide the line between 4 and 5 is the best aligned, so call it 12.45mm, but that’s pretty optimistic precision for a cheap plastic screen-printed caliper!
