Since I've started making things with the 3d printer, I've found the
need for measurement more accurate than a ruler or a tape measure can
provide, particularly of non-cuboid shapes.
The obvious answer is a micrometer or caliper of some sort. Most
calipers now seem to be electronic, but an old-fashioned vernier scale
is still available, no less accurate, and more pleasing to my way of
thinking. (Not to mention not needing batteries.)
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One reads the millimetre scale to the zero on the vernier, then
matches up the vernier divisions with the main scale divisions to get
the sub-millimetre measure if needed. (Here, allowing for parallax,
I'm measuring 43.72mm.)
This particular model will measure inside or outside distances up to
150mm, or the depth of a hole, to 0.02mm accuracy.
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