The circular saw is an excellent tool for fast, straight cutting of timber. It can be used to cut both man made boards (chipboards, MDF etc) and natural timber. Some circular saw models can also cut concrete and masonry if you change their blade first.  

Below is an explanation of how circular saws are sized and advice on what to consider when buying a new circular saw. We also give recommendations on how best to use the saw to ensure safe and effective cuts.  

Circular Saw Size

When you are choosing a circular saw, the first thing to consider is what size you'd require. Different sizes of circular saws are available. They are sized by the diameter of their blade. Many people still use imperial measurements to describe the saws, such as 7¼ or 7½, 8¼ and 9¼”. These are the most common and translate to metric measurements of 184mm, 190mm, 210mm and 235mm respectively. If you're wandering around a display of circular saws, these are what the descriptions will generally relate to. Most jobs around the home can be tackled with a saw holding a blade of 184mm diameter. 

The second issue to consider is the motor size, which has a significant bearing on the power of your saw. Generally speaking, the higher the wattage, the more power your saw will have. Usually the smaller saws (184mm) will have smaller, less powerful motors, while the larger ones (235mm) are fitted with the larger motors. In most cases, a 184mm saw will be fitted with a motor of between 1000 watts and 1500watts, and these are generally more than suitable for the DIY user and most home improvement jobs.

When you get into the more trade-oriented range of circular saws, the motor size can increase to 2000 watts or even more. This makes them pretty powerful and able to tackle an increased range of tasks. For example, you could fit more powerful saws with a masonry blade and cut large amounts of concrete or pavers.

Ease of Use

Bear in mind the weight of the saw. The smaller saws can be quite light (+/- 3kg) and easy to use while the larger models can get considerably heavier (getting up to 7kg) as the blade diameter and motor size increases. 

You can purchase cordless circular saws. These typically have a blade of between 140mm (5½”) and 165mm (6½“) and weigh only a couple of kilos and although they don’t typically have the power output available of their mains-powered cousins, they're fantastic for trimming and finishing work.

Different saws from different manufacturers have a range of handle layouts that can feel considerably different from each other. Most saws have a fairly standard grip at the rear of the saw where the trigger is located. At the front of the saw, the forward handle can range from one that is moulded into the body of the saw through to an adjustable handle that can be altered to suit individual users or circumstances. 

However, depending on where the handles are placed and just how the weight is distributed, the feel of the saw can be altered quite significantly. If a saw doesn't feel comfortable or well-balanced when you pick it up, its likely to feel a even more uncomfortable when youre using it!  

Circular saws are fitted with a spring-loaded guard that covers the blade below the sole plate and this guard retracts as the saw moves through into the piece of material its being used to cut at the time.  

The triggers on circular saws have a two-stage operation, requiring a safety lock-off switch or button to be depressed before the main trigger can be pulled back. Generally, the lock-off mechanism is thumb-operated, and it's designed to prevent the operator accidentally pulling the trigger and causing the saw to function unexpectedly, which could cause danger to the user or others nearby. 

For those of us who are right-handed, the grips, handles and lock-off switches should be fairly simple to operate but, if you're left-handed, take a bit more time to find a saw that's comfortable for you to use. If you want to ensure your cuts are accurate and exactly where you want to them to be, you need to make sure that you can clearly see the tip of the blade when using the tool.  

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Types of Blades
 

There are different types and patterns of circular saw blades available. Each type is to used for a specific purpose. Most saw blade teeth now are tipped with a hard, durable product called tungsten carbide that allows the blade to stay sharper for longer periods. 



Types of Circular Saw Blades for Cutting Timber:  

 
For safety reasons, always ensure the saw is unplugged when changing the blade. If you're looking to cut materials other than timber, check out the range of specialist blades available at your Mitre 10 store, and don't hesitate to ask a store representative if you need some help finding a blade that's suitable for the job you’re about to undertake.
 

The secret to a good power saw is a sharp blade!  This is normally not a job the average home handy person can do. It`s best to get your blades professionally sharpened.

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Advice on Cutting Timber

 
When making any type of cut, adjust the depth of the blade so it's about half a tooth deeper than the product you're cutting. This is important for safety as it reduces the chance of the blade binding and kicking back and it also gives the best cut finish possible. 

One of the most common cuts you can make is a "crosscut".  This is where the blade of the saw cuts at 90° to the grain of the timber, such as when cutting off a length of 100x50 framing timber. On crosscuts, give your saw the best base it has to work from by placing the largest part of the foot plate on the main part of the timber, rather than on the offcut.  

Depress the lock-out switch, pull the trigger and wait until the blade is rotating at maximum speed before attempting to make your cut. On most modern saws, this will only take a second. 

While sighting the blade, move the saw slowly into the timber until you can see the blade start to bite into the wood. If you're slightly off target, adjust the position of the saw until the blade is cutting just to the waste side of your mark or line. 

Once you're in the right position, push the saw through the cut with a gentle, but firm, motion. Do not force it through as you'll place the motor under an unnecessary load, which does nothing to extend the life of your saw as well as creating more possibility of the blade binding. If this does happen, the saw can kick back, so it's a good idea to stand to one side as you're making the cut. 

Many of these guidelines can be used when ripping timber as well. A "rip" cut is where the saw blade runs along the length of the timber grain. With rip cuts you often have to keep more of an eye on the alignment of the footplate in relation to the work surface as you make your cut. This is because many rip cuts are made with the footplate sitting on top of a narrower surface and it's easier to accidentally tilt the saw, making your cut inaccurate. 

Most saws come with a ripping fence as a standard fitting and this can be fixed in place to a desired width and used to guide the saw along the length of timber without the need to constantly keep an eye on the blade as it cuts. Once again, don't try and force the saw through the work - just let it work through the timber at a pace that doesn’t cause it to labour. 

When you've finished cutting, make sure the blade guard has returned to its position over the blade before putting the saw down. If it gets jammed in the "open" position and the saw is placed on the ground or a work surface with the blade still spinning, you'll be in for a nasty shock, so try and make it a habit to check the guard before putting your saw down.

When cutting panels, make sure the work is well-supported and that you're able to safely reach across the panel when making the cut. 

Cutting at Bevels and Angles

While saws are generally used to make square cuts (ie, cuts at 90° to the top face of the timber), cutting timber at an angle is also possible by using the saws bevel adjustment function. This allows the foot plate of the saw to be tilted to 45° (or more on some models), which is the typical angle used when cutting timber for a mitre joint. 

Your saw will have a guide that shows how far the foot plate has been tilted and will typically have marks at 45° and 22.5°. Although cutting an angle includes many of the same principles as square cuts and is done in much the same way, it can often be more difficult. Bevel cuts also reduce the depth of the cut so, if a saw is able to cut through a piece of timber when set at 90°, it may not make it all the way through that same piece of timber when set at 45°. 

To make it easier when cutting timber with the saw set to a bevel, it is possible to purchase an adjustable square designed for use with a circular saw. This can be held on the surface of the work, giving the saw a firm edge for the foot plate to slide along as the cut is made. These squares are useful for making standard (90°) cuts as well and can be adjusted to a range of angle settings for cutting at angles across the face of the timber. If you want to rip timber with the blade set at a bevel, you can also use the saws rip fence at the same time.
 
A circular saw is probably one of the most versatile and effective saws available, lending itself to a wide range of uses. Whether used on rough-sawn, treated timber or other materials outdoors or cutting finishing timber inside, a circular saw can "generally" do the job well if it's set-up and used appropriately. We hope that this guide can help you select the right circular saw to buy and give you advice on how to use your saw effectively.

Our thanks to Black and Decker for their assistance in compiling this guide. View a range of Black and Decker Circular Saws here.