Dimensions of a Micrometer


There are numerous inside micrometer sizes available. The measuring range of some units is 1-1/2 to 8”, but others have a greater range. The graduation of each unit varies, but 0.0001 inch is not uncommon. 

Inside Micrometer Definition 

This is a measuring tool designed specifically to gauge the sizes of interior diameters. The typical micrometer is utilized for outer diameter measurements (i.e., those of a bolt). By contrast, the inside micrometer is used to measure the inner dimensions (i.e., of a nut). 

Design of the Inside Micrometer 

Inside micrometers are designed in different ways, but their function is the same. While the physical dimensions vary, all have a maximum and minimum diameter that can be measured. The most widely used designs are the caliper and tubular micrometers. 

The tubular inside micrometer has a cylindrical tube. This can be inserted into a hole to get the diameter. Depending on the micrometer sizes, thiis tube may also be set between parallel surfaces. After the tube has been placed, the tube will expand until it touches the inner diameter walls. 

The caliper micrometers have a movable caliper set onto a tube. Another tube will be stationary. The movable tube can be modified by the tube length. This will simplify the measuring process. 

Standard and Digital Inside Micrometers 

While there are differences between the two, both depend on a screwing mechanism to show the measurements. In standard inside micrometers, the results can be determined by the markings at the thimble and barrel. 

In terms of operation, the digital micrometers are similar to the standard versions. The difference is they use a digital display to show the readout. Since the results are on the barrel, it will not be necessary to evaluate the thimble. 


In spite of the name, the inside micrometer is not limited to measuring small objects. The tool can also gauge large diameter dimensions accurately. That is one of the reasons why micrometers are available in varying sizes. 

Some sets come with one measurement head and numerous tubes that can be connected to the head. The tubes are of varying lengths, making it easy to measure various inside diameters. These tools can also be used to measure assorted parallel surfaces. 

The importance of the micrometer sizes cannot be overstated. Simply put, the minimum and maximum ranges will determine what kind of objects you can measure. Fortunately, these figures will be included in the product specifications.

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