How to use a micrometer

You need to know how to use a micrometer if you want to measure things properly and accurately.

Why use a micrometer?

A micrometer is just about the most accurate measuring device for objects and distances of less then around 12mm. I mention 12mm because mine is a typical micrometer and that can measure up to 12.7mm. Some can measure larger than this but around an inch is a typical size.

You can measure to within .01 or a hundredth of a millimeter with a micrometer.

You can’t do that with ruler. Even if you use a magnifying glass.

The digital micrometer’s are also easy to use.

How does a micrometer work?

A micrometer looks a little like a clamp. It has a body similar to a clamp and a screw thread similar to a clamp. In fact it is the screw thread that enables the micrometer to measure so accurately or at least to see how accurately it is measuring.

Using a gauge marked around the outside sleeve as you twist the micrometer you can read extra divisions of an inch or millimeter.

A micrometer also has a ratchet device that will slip when you have tightened it enough. Without this you could crush what ever it was you were measuring. I did mention that a micrometer was a bit like a clamp!

Microcomputers were originally made of steel however a lot of the newer, cheaper digital ones are made of carbon fiber.

The digital ones also don’t have to be tightened by revolving them. You just put your thumb on a lever that is sprung return. As you release the pressure off your thumb the measuring faces of the digital micrometer close on the object. The digital display then show the measurement.

This is a lot easier that trying to read the increments from the sleeve and this was one of the reasons beginners made errors which were caused by misreading the micrometer.

Looking after a micrometer

Try to keep your micrometer in a box when it’s not in use so as not to get it damaged. Its a precision device and the better ones will come in a protective case. Whatever you do be careful of the measuring faces as if these get damaged or scratched its going to cause you a headache!

Measuring things with a micrometer

A micrometer can measure many things. In fact just about anything that is less than 12mm or so. They are used commonly to measure the thickness of some thing. I worked at a printers for a while and a micrometer was essential to measure the thickness or paper or cardboard. How else could you measure something that was .37mm thick. Not with a ruler that’s for sure.

They are also excellent at measuring things that don’t have square edges. Something like a sphere for instance. Because the objects being measured fit between parallel measuring faces you can easily measure something like a ball bearing of something with a circular end like the thickness of wire for instance.

Micrometers and CNC machines

I bought mine specifically for my hobby CNC machine. It can move to less than .1mm and can make objects and cut and drill to within that resolution. To be able to do that you need to be able measure stuff accurately. Things like the diameter of a cutting tool and also the thickness of aluminum and perspex sheets. It’s no use trying to cut something to within a tenth of a millimeter if you’ve got a cutting tool that is .2mm too large. Can you tell if something is .2mm too big? I know I can’t.

CNC machine calibration

Calibration for instance was really hard to do accurately. After I had just got my CNC machine working I tried to use a ruler to calibrate it. I laugh about it now but at the time I didn’t have anything else.

I got both a digital micrometer and a digital caliper at the same time as I realised I was going to need both of these measuring tools. If you are unsure whether you need a micrometer or a caliper or both check out my post Micrometer vs caliper to help show you the differences between them.

CNC machines are so precise I think you will agree with me that its practically impossible to use one without a caliper and micrometer.

If you are unfamiliar with what a CNC machine is, so was I a couple of years ago. Basically mine is a router that can be moved around left and right, backwards and forwards and up and down. It uses stepper motors and linear guides.

These move the router around using a computer to .1mm steps.

Using the right software you can get it to cut out shapes of all sizes. I use mine to make complex interlocking project boxes from acrylic sheet and aluminum. If you want to know more about what CNC machines can do read my article here.

Using the digital micrometer

A digital micrometer is a lot easier to use than an analogue one. Most of them have three buttons. Turn it on with the power button and select metric or imperial with the second button. The third button is used to set zero.

When you first turn on your digital micrometer, open the measuring faces with the thumb lever and wipe with a soft cloth to make sure there is nothing on the faces to get in the way of the measurement. Obviously don’t be too vigorous and don’t use anything abrasive. This is a precision measuring tool!

Measuring objects with a digital micrometer

When you measure with a micrometer make sure the item is square with the measuring faces and not at an angle. If its not flat or properly located between the measuring faces you won’t get an accurate measurement.

Sometimes it’s not easy to see if an object is properly seated so I usually measure twice to make sure the readings are the same.