# Understanding Metric Countersunk Hole Sizes

Metric countersunk hole sizes are used in a variety of industries and applications. They are used to create precise holes in different materials to accommodate fasteners, such as screws and bolts. As the name suggests, a countersunk hole is one which has a flat bottom and angled sides that angles upward towards the top of the hole. This creates a flush surface when the fastener is inserted into the hole. In order to create the perfect hole every time, it is important to understand the various metric countersunk hole sizes and which are best suited for your application. In this article, we will discuss the different metric countersunk hole sizes and how to measure them.

## Metric Countersunk Hole Sizes

Metric countersunk hole sizes are typically measured in millimeters (mm). The most common metric countersunk hole sizes range from 2.5 mm to 8 mm. The size of the hole is determined by the diameter of the bolt or screw that is being inserted. For example, a 4 mm countersunk hole is typically used to accommodate a 4 mm bolt or screw. The smaller the hole size, the smaller the bolt or screw that can be used.

## Measuring Metric Countersunk Hole Sizes

Measuring the metric countersunk hole size is fairly simple. The first step is to measure the outside diameter of the bolt or screw that will be inserted into the hole. This measurement will determine the size of the hole that needs to be created. The next step is to measure the depth of the hole. This should be measured from the surface of the material to the bottom of the hole. This measurement will determine the angle of the sides of the hole. The final step is to measure the angle of the sides. This is typically done with a protractor. Once all of these measurements are taken, the metric countersunk hole size can be determined.

## Types of Metric Countersunk Hole Sizes

There are several types of metric countersunk hole sizes. The most common types are standard, fine, and extra-fine. Standard metric countersunk hole sizes have an angle of 82 degrees and a depth of 3.2mm. Fine metric countersunk hole sizes have an angle of 90 degrees and a depth of 2.9mm. Extra-fine metric countersunk hole sizes have an angle of 100 degrees and a depth of 2.5mm. The angle and depth of the hole will determine which type of metric countersunk hole size is best suited for your application.

## Tips for Choosing the Right Metric Countersunk Hole Size

When selecting the right metric countersunk hole size for your application, there are a few tips to keep in mind. First, make sure to select a size that is larger than the diameter of the bolt or screw that will be inserted. This will ensure that the hole is large enough to accommodate the fastener. Secondly, make sure to select a hole size that corresponds to the angle that is required. This will ensure that the hole is created at the correct angle. Finally, make sure to select a hole size that is deep enough to accommodate the fastener. This will ensure that the fastener is properly seated in the hole.

## Metric Countersunk Hole Sizes Chart

To help make selecting the right metric countersunk hole size easier, here is a chart that lists the most common sizes and their corresponding angles and depths:

Size (mm) Angle (degrees) Depth (mm)
2.5 100 2.5
3.2 82 3.2
4.0 82 4.0
4.8 82 4.8
5.6 82 5.6
6.4 82 6.4
7.2 82 7.2
8.0 82 8.0

## Conclusion

Understanding metric countersunk hole sizes and how to measure them is essential for any application that involves fasteners. Knowing the right size to use will ensure that the hole is correctly sized and angled for the fastener that will be inserted. It is important to keep in mind that the size of the hole should be larger than the diameter of the bolt or screw, and the angle and depth of the hole should correspond to the size of the bolt or screw. Understanding these basic principles will help to ensure that the correct metric countersunk hole size is selected for your application.