5 Things to Know Before Buying countersunk machine screw

Machine screws are everywhere; manufacturers use them in everyday applications and also in more complex assemblies. Manufacturers also produce them in imperial sizes, but this blog post will focus on metric machine screws. We will talk about their uses, common head types, common drives and the materials they are usually available in. Additionally, this will also act as a starting point for more specialised posts on the various types available.

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What Are Machine Screws?

Or what is a machine screw? A machine screw is a type of precision fastener that holds two components together. As standard, these screws are typically fully threaded and can be screwed into a tapped hole with a driver. Alternatively, you can be insert them into an unthreaded hole and tightened with a nut, or a nut and washers from the other end.

Manufacturers produce these precision-made screws to strict tolerances, adhering to the exacting standards of both DIN and ISO specifications, with many variations available.

Manufacturers usually produce them in the standard metric coarse pitch and typically make them in smaller sizes than other types of bolts. Furthermore the most common machine screw sizes range between M1.6 – M6 but they can also less commonly be available in larger diameters.

These screws are virtually always fully threaded from just under the head to the end of the screw. The tip of the screw is always flat and not pointed.

What Are Machine Screws Used For?

All sorts of industries widely use machine screws. Common uses are to attach various materials like boards and panels in many materials like plastics and metals etc.

They are an essential component in manufacturing, automotive, electronics, assembly and construction, to name a few of the more common industries.

Machinery Manufacturers commonly use them in the assembly of their machines, hence the name machine screws.

What Are The Different Types Of Machine Screws?

There are many common machine screw types and some not so common. I will focus on the main everyday readily available ones.

Clicking on any of the links below will take you to a more in-depth post on each type of machine screw. You can learn more about each one and their unique characteristics.

How Do I Decide What Machine Screw To Use?

When deciding what machine screw to use for your application, you should take the following into consideration.

• Head type: Will the head obstruct anything? Should a countersunk machine screw be used so that the head sits is flush with the material? Or is a raised type head like a pozi pan head machine screw ok?
• Drive type: Does a lot of torque need to be applied, are there any special considerations that should be taken into account?
• Material: Are these going to be used outdoors or in an environment where they could rust?
• Sizing: Ensuring you have the correct size of screw is important, thread diameter needs to be spot on if screwing into a threaded hole. Length can also be critical if screwing into a hole with limited clearance or if a nut needs to be screwed onto the other end of the machine screw

What Sizes Do They Come In?

Everyday production primarily uses the following machine screw sizes.

Machine Screws M1.6

Machine Screws M2

Machine Screws M2.5

Machine Screws M3

Machine Screws M4

Machine Screws M5

Machine Screws M6

As for, what length are machine screws. They come in varying lengths from different manufacturers and can vary depending on the drive type and material.

How Do You Measure A Machine Screw?

This can be a cause for confusion to many people, I will explain below how to go about measuring a machine screw.

To measure a countersunk machine screw, you measure the entire length from the top of the head to the end of the thread. However, you measure machine screws with a raised type head, like a pan head machine screw, differently. Unlike countersunk screws, you measure them excluding the head, starting from under the machine screw head to the tip of the thread.

On smaller diameter screws it can be near impossible to measure the thread diameter with a ruler. It is advisable to measure the outer diameter of the threads with a digital caliper. To give you an accurate measurement use one that measures in hundredths of a millimeter.

Example of how to work out a machine screw size:

The “m” size represents the outer thread diameter measurement. If the thread diameter measures 5mm, then the screw is an M5.

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Depending on if you were measuring a countersunk or a raised type head screw. You would use the rule mentioned above to get the length of the screw. Let’s say the length is 20mm.

In conclusion then , if you had a screw at 5mm diameter and 20mm length then it would be an M5x20

Where Can I Find A Machine Screws Size Chart?

On all of our machine screws product pages, on the right hand side near the top there is a tab called Product Dimensions, you will find the dimensions for each type of screw on there.

If you click the links next to the images above, you will find a dimensions chart on each of the related blog posts for each type of machine screw.

What Are Machine Screws Made Of?

Machine screws come as standard in many different materials for various applications. You should give consideration to environmental factors and strength requirements when deciding what material to use.

Some of the most common materials that a machine screw is made of include bright zinc-plated steel, as well as yellow zinc-plated and black zinc-plated. A2 stainless steel & A4 stainless steel, brass and nylon.

Do Machine Screws Need Nuts?

This all depends on what you are working with and will vary from application to application. Often, a machine screw will be screwed into a pre-threaded hole with or without a washer and tightened using a screwdriver.

Alternatively, they can also be inserted through aligning pre-drilled holes and fastened together with a nut and washer if required.

Will Machine Screws Rust?

If you consider the environment that machine screws will be exposed to and make an informed decision on the material used then they will not rust.

Just a couple of examples. If you are using machine screws outdoors then A2 stainless steel would be a good choice. If however you use them in or near salt water then A4 stainless steel would be a better option.

Conclusion

Machine screws are fundamental to many aspects of modern assembly and manufacturing. With a better understanding of their types, materials, and applications, along with proper selection and installation, you can tackle any project with confidence.

More detailed specific information on the various types available is provided on the related blogs posts for each type of screw. You can click any of the links above to read more about them. You will also find some useful machine screw size charts there as well.

Hope this post was helpful.

What is a countersinking screw? The countersunk head screw is also known as a flat-head screw. It has a smooth head and a tapered bottom, allowing it to blend naturally into the surface of the object it secures. Without looking carefully, it can be difficult to spot. Now, let’s discuss its types, standards, and uses in detail.

Types of countersunk screw  

Categorize by Thread

There are many varieties of countersunk head screws(flat head screws), and they are divided into two types according to the shape of the tail. One is countersunk head pointed tail screws, which all have pointed self-tapping threads. For example, wood screws, self-tapping screws, deck screws, and Drywall screws are all pointed countersunk head screws.

The other is countersunk head flat tail screws, also known as machine screws, which are usually made with fine threads.

Categorize by Driver Type

There are also many driving methods for countersunk(flat) head screws, such as Philips slotted, flat slotted, trox slotted, pentagonal slotted, inner hexagonal slotted, triangular slotted, etc. These screws can also be made into self-tapping threads or machine threads.

The standard for countersunk screws

Machine screw type standard

The international standards for countersunk head machine screws include DIN799/ISO/JISB hex socket screws, DIN965/ISO flat head cross slotted screws, DIN963/DIN964/ISO/JISBF flat slotted machine screws, ISO/trox counter sunk head machine screws, etc.

The standard for tapping thread flat head screw

ISO/JISBF cross self-tapping screw, DIN/ISO flat slotted self-tapping screw, ISO Hexalobular socket countersunk head tapping screws, DIN Chipboard Screw, DINP cross Self-drilling, etc.

Countersunk screw dimensions   

The common sizes of countersunk head screws range from M2 to M30, M2, M3, M4, M5, M6, M8, M10, M12, M14, M16, M20, M22, M24, etc. The length ranges from 10mm to 100mm. Of course, if you want to buy larger specifications, you can contact us to customize.

What is the angle of a countersunk screw?

The conventional screw countersink angle is 90 degrees 110 120 degrees, but the countersunk head screw angle for aviation is 100 and 130 degrees. You can also customize the screw angle according to your needs.

What is a Counter sunk screw used for?

Countersunk head screws can be divided into the following categories according to application scenarios

1. The furniture industry, such as sofas, beds, tables, and benches are all assembled with this kind of screw. The countersunk head can be embedded in wood, and there will be no protruding parts that will affect the beauty.
2. In the construction industry, stairs, doors and windows, railings, and many other places are fixed with countersunk head screws.
3. In the appliance industry, it can be used to fix the shell and internal parts of TVs, air conditioners, refrigerators, and other household appliances.
4. Machinery industry, assembly of some precision machinery such as CNC lathes, connection and fixation of parts.
5. In the automobile industry, countersunk head screws are also used from automobile body to engine group, including internal electronic components.
6. Corrosion-resistant countersunk head screws such as titanium alloy or stainless steel are used in the aviation industry, wings and fuselages, landing gear, engine parts, and interior of passenger aircraft.

What are the advantages of countersinking screws? 

Countersunk head screws have many advantages such as beautiful and diverse shapes, low cost, simple installation method, space-saving, good fastening effect, low maintenance cost, easy disassembly, and wide range of adaptability.

Installation and disassembly of countersunk screws

Before installation, the position of the screw should be marked first, and the hole should be reamed with an electric drill according to its head angle. The hole should be slightly larger than the conical head of the screw. After reaming, choose a screwdriver or tool corresponding to the groove type to tighten it.

The disassembly method is also very simple. Unscrew it in the opposite direction with a screwdriver. The rusty screw can be soaked with some lubricating oil for a while before unscrewing it. When the screw is broken or difficult to take out, a special tool must be used to remove it.

Summary