How to choose a circular saw
First you have to ask yourself: “What am I supposed to do with a circular saw…?” Once you have asked yourself the question you can also think of the answers. The circular saw is a tool that only makes straight cuts, either freehand or with the help of guides available in manufacturers’ catalogues or self-made. The cuts you are going to make with the circular saw can be perpendicular to the piece to be cut or with an inclination up to 45° but always straight, so if you want to make curved cuts the circular saw is not for you but you will have to get a jigsaw. Including this aspect we see what are the basic characteristics of a good track saw.
What should we consider in a circular saw?
The diameter of the blade
I would say that the first parameter is the diameter of the blade, the greater the diameter and the greater the maximum depth of cut we will have. Hobby circular saws generally have blades from 140 mm to 190 mm with a respective cutting depth, depending on the model, from 40 mm to 70 mm. Needless to say, circular saws with a 140 mm blade are very limited tools as they are generally also of low power, very economical and of approximate construction, it is better to leave them alone and switch to a model that has at least a 160 mm blade that can cut boards up to 50 mm thick and will prove to be much more useful. The ideal would be to choose a circular saw with a 190 mm blade that is a size that satisfies both the hobbyist and the professional, can count on a wide availability of blades and has generally a power adequate for all processes, the circular saws of larger sizes are reserved for demanding uses in the professional field and not suitable for DIY while a circular saw 190 mm is an optimal choice because it can cut from thin panel to thick board. However, the depth of cut is not only influenced by the diameter of the blade but also by how the circular saw is built, so in your choice you will have to examine the technical characteristics of the various models and in particular the maximum depth of cut both at 90° and 45°, you will realize that even with the same blade diameter they can be different.
The power of the motor
The circular saw you choose will have to have a motor of adequate power for the work it has to do, so if you think that you will only use it to cut 15 mm plywood panels you will be fine with a circular saw with a motor of 800/900W, while if the wood you like to work are thick well seasoned boards you will need a machine with 1200/1500W under the hood. A motor with adequate power means faster, cleaner work with less wear on the mechanical parts and the blade, less overheating of the electrical parts and the blade and therefore also of the piece you are cutting. Contrary to what one might believe, a more powerful engine consumes even less electricity because the indicated power (e.g. 1500W) is intended as maximum power consumption, so a smaller engine that goes under stress will consume more than a more powerful one that does its work effortlessly.
The sole material
As an elegant person can be recognized by shoes, a quality circular saw can be recognized by the material of the sole (or shoe…) and there are essentially two types: made of pressed steel sheet or die-cast metal alloy, the first usually comes with a cheap circular saw while the second is mounted on medium-high class tools, what’s different? Due to the material and workmanship, the sheet steel sole is not accurately shaped, its edges are rounded and is quite rough as opposed to the die-cast one, which is much more precise because it is made from a mould. The pressed steel sole also tends to flex and can twist both with use and accidental impact and a circular saw with a not perfectly flat sole will produce cuts that are not straight and not perpendicular, while the cast sole is much more rigid and resistant and maintains its flatness even after many years of intense use, also these types of sole allows a better design of the anchorage points to the body of the circular saw ensuring a more solid whole. So when you go to choose a circular saw give preference to those with a die-cast sole, you will not regret it.
The quality and robustness of the adjustments
The circular saw has two adjustments: the cutting height adjustment and the lateral inclination adjustment, both must be able to be carried out without tools and must be able to be tightened with solidity and precision, once you have established an adjustment and fastened it, it must remain stationary at that point and must not move even after repeated cuts, otherwise you will get uneven cuts or worse if the fastening fails suddenly you may even risk an injury.
The presence of mechanical and electronic protections
Safety in the use of a circular saw is very important and for this reason a quality circular saw has the appropriate mechanical and electronic protections. The main mechanical protection is the protection of the blade which lifts automatically when it comes into contact with the workpiece and which covers the blade once the cut is finished. The blade protection prevents accidental contact with the user’s body or with other objects in the working area, it is controlled by a traction spring that can loosen over time, if you find that the spring is no longer able to quickly bring the blade protection back into position it is better to replace it. Another mechanical protection is the dividing knife that is located behind the blade, not all circular saws are equipped with it, the dividing knife prevents the cut wood from closing around the blade causing stitching or blockages, it is generally retractable and adapts to the depth of cut, in the choice of your circular saw, prefer one that has it. There are essentially three electronic guards: the safety button which must be pressed together with the start button and which prevents unwanted starts, the soft-start soft start and the electronic brake which prevents the blade from continuing to turn after the start button has been released. A good circular saw must be equipped with all these devices.
Two words about blades
As in any cutting tool, the circular saw is also a cutting blade, so even the best circular saw if it is not equipped with a quality blade and suitable for the type of cut you are going to make will give poor results. What are the rules for choosing a good blade? For long vein cuts a blade with few teeth, from 12 to 24, is suitable, this is because a blade with few teeth discharges the sawdust better and advances more easily in the wood while a blade with thicker teeth is more difficult, warms up more and would tend to get stuck, on the other hand the cut with a blade with few teeth is less clean. For cutting through vein or on panels and laminates it is better to use a blade with more teeth for greater precision and cleaning, we are talking about blades with 48 to 80 teeth. Always choose quality blades for your circular saw, generally if you buy a brand circular saw such as Bosch, Makita, Metabo or Festool, they are equipped with suitable blades, but if you have chosen a cheaper circular saw I recommend you to replace the blade with a Bosch, CMT, Freud, Festool suitable for the type of cut you need to make and always mount the right blade for better results and work safely. Saw blades with the teeth shown can be sharpened either by hand or at a sharpening centre.