How to read the digital micrometer

Step1: The digital micrometer can provide high precision reading with the LCD display. So you can get the reading directly from the large LCD display. For example, the reading is 14.054 mm in the picture.

You can also get the reading by reading the marks on the sleeve and the thimble. Usually, we mainly get the reading from the large LCD display for the digital micrometer because the digital reading is more accurate. The reading on the sleeve and the thimble is just for reference. Step2: Read the markings on the sleeve and the thimble, firstly, read the point which the thimble stops at it on the right of the sleeve (It is 14mm here, because each line above the centre long line represents 1mm while each line below the centre long line represents 0.5mm).

Secondly, read the markings on the thimble, it is between 5 and 6. So you need to estimate the reading. (It is 0.054mm for each line here represents 0.001mm). At last, add all the reading up: 14mm + 0.054mm=14.054mm. So the total reading is 14.054mm.

Types of Digital Micrometers

Let's look more into the various types of Digital Micrometers. As I mentioned before there are basically Digital Micrometers measured for external dimensions and internal dimensions. Digital Micrometers is Micrometers with a Digital scale to enhance the ability of a Micrometer to measure precise dimensions. In today's market Micrometers with dial and digital read out are commonly available. Based on this let's list out the various types of Digital Micrometers available.

Outside micrometers

Outside micrometers are used for measuring outer dimensions, like the thickness of sheet stock or outside diameters of round stock. The screw thread micrometer is a type of outside micrometer used to measure not only the diameter of screws, but also the pitch of their threads. The object to be measured is placed between the stationary end of the micrometer, called the anvil, and the moving end, called the spindle. A knob, called a ratchet, is turned, pushing the spindle against the object. The thickness may be indicated by a mark on a vernier scale or by digital display.

Inside micrometers

Inside micrometers are used for measuring the inside dimensions of an object: the inner diameter of a tube, bushing, cylinder, etc. They consist of a micrometer head, a set of extension rods, and in some cases a handle. The length of the head itself is what is measured, since it is placed within the diameter being measured; the smallest heads available are one-quarter-inch. The extension rods are used when the maximum length of the head is too small for the opening. The handle is used for inaccessible places, and the diameter is read from a vernier scale or a digital display.

Depth micrometers

Depth micrometers are used for measuring the depths of blind voids, grooves, recesses, etc. A flat surface at the top of the hole is required for the micrometer base to sit on, and the micrometer should be held firmly in place for an accurate reading. The ratchet is turned until the spindle touches the bottom of the hole, and the depth is read from the vernier scale or digital display.

Bore and Tube Micrometers

Bore is essentially the inner diameter and shape of a cylinder. Bore micrometers, also called bore gauges, are similar in use to inside micrometers, but function in a different way. They read a value relative to the known vale of a "master" bore, such as a preset micrometer, and their precision also allows measurements of ovality or deviations in shape.

Tube Micrometers are essentially outside micrometers that have been modified for measuring the thickness of the walls of tubes and other cylindrical objects.

Picture of Digital Micrometers

Digital Micrometers comes in different shapes and sizes from different manufacturers. Here is a picture of a simple Digital Micrometers with fine adjustment which is most widely used in metal working industry.

History of the Micrometers

The First Micrometers

James Watt invented the first micrometer in 1772 as a way to improve the production of large equipment during the Industrial Revolution. Manufacturing companies were having trouble assembling consistent products because there was no suitable way to precisely measure small distances. Watt's micrometer consisted of two jaws that could be moved up and down by turning a threaded spindle. The piece to be measured is placed between the jaws, and the micrometer is adjusted until the jaws touch the item. The dial displays the distance between the jaws.

The Lord Chancellor

In 1805, Henry Maudslay developed his "Lord Chancellor" micrometer. The design was similar to Watt's, with two plates connected by a threaded screw. The screw contained 100 threads per inch and included an index wheel with 100 marks around the outside. This gave Maudslay's micrometer amazing accuracy for the time, allowing it to measure down to one ten-thousandth of an inch.

Joseph Whitworth

A former employee of Maudslay, Joseph Whitworth improved upon the Lord Chancellor's design, introducing a micrometer that could measure to within one millionth of an inch. The design was so innovative at the time that it was displayed at the Great Exhibition of the Works of Industry of All Nations in London in 1851.

Jean Palmer

The first portable micrometer was built in France by Jean Palmer. It was small enough to be operated with one hand, making it possible to measure metal sheets or other parts at any point on the assembly line. While the design has been refined over the years, Palmer's portable micrometer was very similar to the models in use today. Known as the Systeme Palmer, this micrometer design was shown at the 1867 Paris Exposition.

Brown and Sharpe
American engineers J.R. Brown and Lucian Sharpe saw the Systeme Palmer in Paris and realized it was the solution to a problem that had been plaguing them. At the time, there was no good way to measure sheet metal, leading to customers returning shipments because they were not the correct thickness. They modified Palmer's design and received a patent in the United States in 1899, leading to the first mass-produced micrometer

Accuracy of Digital Micrometers

Digital micrometers provide 10 times more precision and accuracy: 0.00005 inches or 0.001mm resolution, with 0.0001 inches or 0.002mm accuracy. The main disadvantage is that they cannot measure lengths or widths more than 1 inch in size.

Micrometers

Micrometers are the simplest tools used for measuring. When since and technology started its development the need for measuring equipments aslo araised. Micrometers are one of the oldest form of measuring tools. Lots of developmenst have come since then and todays Micrometers are equipped with vernier scales to digital scales.

Digital Micrometers

Digital Micrometers are device for accurately measuring very small distances : modern micrometers are accurate down to one ten-thousandth of an inch. The four basic types are the outside, inside, bore, and tube micrometers. Depending on the application, they may be table top instrumens or small hand-held tools. We will discuss more about digital micrometers in the comming posts