A car engine (of the traditional internal combustion variety) contains about 200 discrete parts
, and all 200 live right next door to each other inside the engine block as they perform their functions. These neighbors get along because they’ve been carefully zoned—each part is just the right size for its area.
Let’s say that we’re building an engine from scratch. We’d have to be sure that our 200 parts will all fit snugly in their engine block, which means a whole lot of measuring.
Enter our precision tools: the micrometer and the caliper. Here are some of the key similarities and differences between the two.
Micrometer and caliper: patron saints of the tiny
When you need to take measurements in the thousands of an inch, you’ll be reaching for your caliper or your micrometer. These tools are both handheld, made of mostly metal, and use tightening mechanisms to hold the things you want to be measured in place.
To find the diameter of a quarter, for example, you could use either device, employing essentially the exact same order of operations.
With either one, you place the quarter between two prongs (for a micrometer, these are called the anvil and the spindle; for the caliper, these are called the jaws), and then press the prongs together to keep the quarter still. The diameter is then provided by the device.
Extreme accuracy vs. pretty darn good accuracy
Though both are great for tiny measurements, micrometers and calipers have subtle differences between them.
Micrometers take the trophy for accuracy, boasting ten times the accuracy of calipers. In part, this is because, reports Machinist Guides
, micrometers have safeguards against user-induced extraneous force that could change a measurement. Their “ratchet stops” ensure that what is applied is even and replicable so that measurements are accurate.
But this boost in accuracy comes at the price of convenience and mastery: they have more complex machinery, are harder to read, and sometimes need more than two hands to correctly manipulate. Plus, they only do one kind of measurement.
Calipers, by contrast, are easy to use, cheaper, and versatile in their use cases. They’re a bit like pliers—you just grab (using one hand) the thing you want to measure between the jaws of the caliper and press down until it’s framed and you can see what the ruler says.
And that’s just the beginning of its capabilities. If you want to measure inside an object or get its depth, the hidden compartments and rods of a caliper can do that for you too. Calipers: tiny, not perfectly accurate, but mighty.
Why not both?
So which is better for your engine build, the micrometer or the caliper? The answer, you might have guessed, is both.
For parts that don’t require accuracy to the ten-thousandth of an inch, use the caliper. For anything that needs obsessive attention to detail, use the micrometer.
And if you really want to feel secure, you could always use the micrometer to get your fine-grained analysis, and then turn to the caliper to make sure nothing crazy happened. You know what they say…measure twice, cut once.
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