The not-so-secret way to make sure your projects work out well is by taking accurate measurements. They say, “measure twice, cut once”, but if you can’t take precise measurements in the first place, you might as well not bother! Digital calipers are tremendous bits of kit, you can use them to take all sorts of readings if you know how to use them.
Probably the most used function on a digital caliper is to take outside measurements. This is the distance from one end to the other of an object. Just like using a basic ruler, you’re measuring from end to end using the big jaws that hang underneath the display.
If you need to work out the distance between two objects, you need to take an inside measurement. Think about measuring the inside of a piper, for instance. You can’t easily replicate this task with a basic ruler, you need to use the smaller set of jaws found on the top of the tool. The jaws face outwards, allowing you to fit them between two surfaces get an accurate measurement.
The best digital calipers will include a long probe that slides out for checking depths. It’s usually stored inside the ruler section of the caliper and is thin enough to get into the tightest spots.
Taking measurements with the inside or outside jaws isn’t always ideal. If you want to get a precise measurement of the inside of a container, you can use the step function. The flat end of the moving jaw can be used to take measurements. You move it into place, and then use the offset part of the blade to measure the distance between there and the flat end of the caliper.
Sometimes you need to move the jaws or depth probe by just a fraction of a millimetre. It can be difficult with big, clumsy hands, so make use of the fine adjustment wheel. Usually sited on the opposite side of the display to the jaws. You can roll it either way for the highest level of precision.
Metric or Imperial Measurements
It doesn’t matter what side of the unit debate you’re on. You can switch between codes with the press of a button. Whether you’re a metric fanatic or Imperial stickler, it’s seriously useful to have both.
Decimal and Fractional Imperial Measurements
When you’re measuring objects using Imperial inches, things can get complicated. Measurements less than one inch can be shown in two different ways. Decimal inches use numbers behind a decimal place, and fractional inches use fractions. For example, half an inch can be displayed as either ½ or 0.500. The best digital calipers can switch between these two modes.
This is one of the key features found on only the best digital calipers. Making reference measurements is easy and will improve your calculations without having to do any mental maths. If you want to compare, say, the thickness of several parts you’ve machined, this is the way to do it. Measure the first one, then zero the measurement. You can then measure the rest, and instead of showing the overall measurement, you can see just the deviation.
For example, if I machine four blocks of steel I can compare them for relative size without needing to remember four different numbers. The first block is 10.000 mm. I zero the calliper and then measure the second. It now shows 0.014 mm. The third shows -0.001 mm and the fourth 0.008 mm. I now know the difference in measurements and can decide if they’re within design tolerances.
The best, and most expensive, digital callipers come with a certificate of calibration. The Mitutoyo 500-196-30, for example, comes with a stamped and signed document that guarantees calibration from the factory. You know that it will read correctly and will repeat the measurements you make.
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