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.
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.
Pozi Pan Head Machine Screws
Phillips Pan Head Machine Screws
Slotted Pan Head Machine Screws
Torx Pan Head Machine Screws
Pozi Countersunk Machine Screws
Phillips Countersunk Machine Screws
Slotted Countersunk Machine Screws
Torx Countersunk Machine Screws
Pozi Raised Countersunk Machine Screw
Slotted Raised Countersunk Machine Screw
Slotted Cheese Head Machine Screws
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.
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.
Do you need help or advice on anything you are not quite sure about? Email us on sales@boltbase.co.uk or call us on 01259 218830. We are always happy to answer any questions you might have.
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