How to Read a Digital Caliper

A digital caliper is a precision tool that can be used for the accurate determination of the dimensions of a lot of objects which may be difficult or practically impossible to use a meter rule.

Just like any other precision instrument, it is essential that it is used properly and taken care of the right way. There are some important precautions you should take in order to end up with accurate results.

One of these precautions is that you shouldn’t operate a digital caliper near a strong magnetic field. Also, there should never be an application of voltage via any source at all in order to protect the circuit.

Similarly, before you use the caliper, unlock the top thumbscrew and clean the jaws. Move your finger over both jaw surfaces gently but firmly. The jaw tips should be specially cleaned thoroughly. That’s because of the chance of an accumulation of grease, small particles, and dirt.

Cleaning of the jaw tips guarantees that the setting of the zero position is not affected. After you finish the cleaning, close the jaws together and press the zero button to set the caliper’s zero points.

Digital caliper lying on a surface

In order to preserve the flatness of the jaw surfaces, you shouldn’t apply pressure while rotating the piece in the jaws. Especially when you are measuring round stock. Instead, simply open the jaws, rotate the bar and then close the jaws to take the measurement.

Furthermore, in addition, you can use the thickest part of the jaws to take measurements. If you use the thin knife-edged jaw tips repeatedly, this could lead to excessive wear.

Making use of the thick part also helps to get rid of any tilt present between the workpiece and jaws. Or it can actually lead to the measurement including an error.

How to Measure Using Digital Caliper?

Now to the actual reading of a caliper, there are five entirely different and unique ways to measure using a digital caliper:

  • Outside Measurement (by using the large jaws).
  • Inside Measurement (by using the small jaws).
  • Depth Measurement (by using the depth gauge).
  • Step Measurement (by using the head of the calipers).
  • Difference Measurement (by using any jaw and a reset of the zero position).

The first and last step before taking any measurement is to make sure that your calipers are at zero. Missing this particular step could lead to inaccuracies in your subsequent measurements.

If your caliper displays an inaccurate value as its zero value and you will have to set it back to actual zero, all you have to do is press the zero button and then close the jaws to see if it would remain at zero. If it does, then, you are good to go.

Some calipers are programmed to always have an accurate zero position, however, it is still essential to check. For each of the different measurements mentioned above, here are the processes detailing each measurement:

Mechanic measures with digital caliper

1. Outside Measurement

For taking outside measurements, use the lathe jaws on the digital calipers. They are useful for the measurement of the outside dimensions of various objects irrespective of size or shape.

You could measure a metal rod, machine parts, a bolt head, a lumber section, and a range of other objects. To begin taking measurements, start by measuring the outside dimensions, it’s your first closing the calipers.

Then press the zero button to recalibrate the calipers, especially if it has been used for previous measurements. This is useful to ensure that you get the correct results.

After doing this, open up the caliper and place the large jaws of the caliper around the object to be measured. Manipulate the thumbscrew present on the caliper until to close the jaws around the object until the jaws come in firm contact with the object.

As a precaution, do not pull it to tight to avoid damaging the jaws. And do not set it too loose either to avoid getting inaccurate results. This is why it is better to tighten the thumbscrew gradually so as to make only the appropriate amount of contact with the object.

After this is done, then, read the measurement that would be present on the indicator.

Mechanic makes inner measurements

2. Inside Measurement

Use the smaller jaws on digital calipers for inside measurement. The inside dimensions of objects request a smaller size of jaws. That’s why you can’t use the larger jaws for outside measurements.

With reference to inside dimensions, some of these include the space between the keys on the keyboard on your computer system, the distance between radiator fins.

The inside hole of a washer and even the determination of the diameter of an already present hole to guarantee an accurate selection of the correct size of bolt diameter or drill bit to make use of is done using the digital caliper’s smaller jaws.

In order to carry out the measurement, you’d need to close your calipers. It’s just like you did when taking the outside measurement. Since it is a new measurement, press the zero button to recalibrate the calipers in order to guarantee an accurate measurement.

Next, insert the digital caliper’s small jaws into the hole while still leaving it closed. Afterward, grip the thumbscrew and begin to open the calipers slowly until the two jaws make contact with the object firmly.

As always, make sure it isn’t too loose so as to get an accurate measurement nor too tight and not damage the jaws. Then read the measurement that you can see on the digital indicator.

3. Depth Measurement

You shouldn’t do the determination of depth using the jaws on the caliper unlike inside and outside measurements. Every typical pair of digital calipers usually comes with a depth gauge which is usually found at the base.

You can usually find this depth gauge in most digital calipers except in very rare cases. This depth gauge which is also known as a depth probe would be inserted into objects and be used to determine just how deep a cutout or a hole present in an object is.

The process of taking this measurement is very similar to the others above although it may vary just a little bit.

For depth measurement, you would need to close the calipers and press the zero button in order to guarantee that you are getting accurate results. Next, position the base of the digital caliper over the hole or cut out. Then use the thumbscrew to lower the probe into the object very slowly until it comes in contact with the bottom.

When you are certain that you set the caliper the right way and position it perfectly, read the measurement that already displays on the screen. However, while carrying out this process, recall the precautions that are necessary in order to avoid errors.

Inner measurement with a caliper

4. Step Measurement

Unlike taking the inside measurement and outside measurement, not all calipers come along with the features required for taking step measurement. For most standard calipers, however, you would find the features for step measurement.

In case your caliper is not suitable for taking step measurements, you can make use of the depth gauge present in a pinch to substitute for this particular function in a pinch. This implies that you are not a newcomer here and you know how to go about it.

Step measurement usually makes use of the caliper head to determine the step difference between two material sections. Just like measuring a typical staircase with steps, the caliper’s bottom jaw would typically rest on the lower step while the top jaw would make contact with the subsequent step.

This way you can easily determine the measurement by looking at your digital screen just like every other measurement. This measurement feature is highly essential especially in designing a building scale for larger items as well as working with small objects.

5. Difference Measurement

You can do the different measurement in combination with any of the measuring choices already mentioned. Difference measurement simply provides you with the difference between the dimensions of various objects.

In order to carry out a difference measurement, the first step is to close the calipers and press the zero button. It’s just like the other measurement processes. Next, using any of the measurement methods already mentioned in this post, take your first measurement.

Next, press the zero button without closing or moving the calipers at all. Then measure the second object using any of the methods already discussed.

A measurement would show on the display screen. The value displayed by the digital caliper indicates the dimensional difference between the two objects. Some better advanced digital calipers come with a button called “reading hold”. It provides an alternative to having to adjust the calipers back to zero.

To apply the reading hold feature, take your first measurement, press down the reading hold button. Then proceed to take your second measurement. The caliper would then automatically determine the difference between both and display the accurate result.


Bottomline

Precision instruments are called that because they are known for taking precise measurements. It is therefore essential to ensure that they continue to carry out this function. This can only be done by ensuring that they remain in prime condition. It implies that you would need to be very careful with your digital caliper.

Carry out all the necessary maintenance processes and observe the necessary precautions in order to guarantee that you continue getting accurate results. This combined with your already gained knowledge of using your digital calipers the right way would easily make this a reality.

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