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Selecting the right screw for the job can be a tricky proposition, particularly when you are buying them online, as we are tending to do more and more these days. Screws, of all the fixings, seem to be the most complicated largely because there is so much choice out there.

Selection of screws and nuts and bolts

How to get the right screws for the job?

In light of this and the many times that we, at DIY Doctor, are asked which type you should use we have put together out three step guide to choosing the right screw for the project you are working on. Here it is:

Choose the Right Type of Screw

Select the right type, such as a wood screw for wood, masonry screw for concrete and masonry, etc. It sounds obvious when said like this but when you start to get to lesser used materials ( even MDF and Chipboard) then it can become confusing, particularly when different types should be used on the same material internally and externally. If you have a project and you want to find out which type of screw to use have a look at our table for selecting the right screws.

Get this right step and you are halfway there. Thankfully most online searches will come up with the appropriate results is you search for ‘the material’ and the ‘screws’, eg. “Decking Screws”. (Try this by searching in our own store – the search box is in the top of every page)If you do this, make sure that you read the description to make sure that they are appropriate for the use you intend.

DIY Doctor Superstore

The DIY Doctor online superstore

Often the results you get from your search are for “General Purpose” or Multi-Purpose screws. The problem is that you don’t really know which of these the right ones for your project are, and they are quite a few variations within these broad categories. At this point you need to know a little more about screw to make the right choice.

Different types of screws

A selection of different types of screws

Pick the Right Screw Features

The thread, tip, and head of screws all vary for different applications, which makes them more or less suited to particular jobs. If you understand what these variations mean then you’ll pick the right one.

In summary, the thread will determine the speed that it can be driven in and how it will hold. The head will hold the drive and transfer the force from the driver into the screw, but it will also stop on the material being fixed to hold it. These features determine the overall effectiveness. Read all about the screw features in our project here.

Different threads and screw points

Several diffenert types of thread and screw point type

Select the Right Screw Size

Again this can be confusing if you are not holding the screw in your hand, as will be the case when buying online.

There are no rules to govern which one you should use, and most if it is common sense; It should not be too large so as to go right through the material you’re fixing, and it should not be too thick so as to split it. If the force is a pulling force, then it should be longer (with wider/more thread), but is the forces that the fix is going to experience is lateral, then a thicker one should be used.

The areas where there is greatest confusion is how the sizes are actually described, particularly when both metric and imperial sizes are used. The length is generally relatively easy to work out but the gauge is a different matter! Have a look at this table to understand the different screw sizes.

Dimensions of a screw

The different dimensions of a screw and how they are measured

If you follow these three simple steps you will be able to ensure that you get the right screw for the project that you’re working on. Hopefully we have taken some of the mystery out of selecting the right screws!


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