Circular saw blade
A circular saw can be used to reliably cut wood, metal, plastic and even building materials such as concrete or natural stone. The cutting work is carried out by the circular saw blade. As there are different types of circular saw blades, a certain amount of basic knowledge is helpful. This guide tells you everything you need to know about the right circular saw blade.
What is a circular saw blade
A circular saw blade is a rotating cutting tool that is used in fretsaws or hand-held circular saws. Regardless of their specialization, all circular saw blades have some properties in common:
- Round shape
- Cutting teeth on the circumference
- Suitable for cutting various materials
However the base material, the number of saw teeth and the intended use can vary.
Generally speaking, there are two types of circular saw blades that differ in terms of their manufacture and design:
- One-piece saw blades: punched out of a base material and fitted with the desired tooth shape
- Composite circular saw blades: made from a metal core onto which cutting edges (teeth) made from other materials are soldered
Short rip and crosscuts in hardwood and high cutting quality in softwood are easily possible with one-piece circular saw blades. Composite circular saw blades, on the other hand, are better suited to hardwood and harder composite materials. This is due to their interlocked (alternately arranged) row of teeth, which is wider than the metal core of the blade and runs through hard materials with less friction.
There are a total of three tooth positions for circular saw blades:
- Negative
- Neutral
- Postive
It all depends on the position of the teeth
In the negative position, the cutting angle in the material is very flat, which is why a lot of force is required. This type is primarily intended for cutting hard metal such as stainless steel.
With a neutral tooth position, there is no rake angle to the centre axis and the entire tooth edge takes the burden. This also requires a high feed force, but the tooth edge is very robust when it hits the material. Circular saw blades with a neutral position are suitable for various metals and light metals.
The positive tooth position is typical for sawing wood. The teeth bite into the material and thus already perform feed work independently. The tips in particular are subjected to heavy loads, which is why foreign objects such as nails or screws quickly damage the teeth.
Finding the right circular saw blade
Four characteristics play a key role in selecting the right circular saw blade. The number and type of teeth, the cutting width and the speed of the blade are also important.
Number of teeth
The more teeth a saw blade has, the finer the quality of the cut. Depending on the material to be cut, however, a high number of teeth is not generally recommended. Like the tooth position, there are also three categories here:
- Low: up to 36 teeth, large chip gap, cutting performance is the focus, cutting quality is coarse and rough, cuts best along the grain
- High: between 36 and 48 teeth, crosscuts achieve clean results, saw blades clog up quickly with longitudinal cuts
- Very high: 60 or more teeth, very fine cutting quality, used for thin materials such as plywood, with slow cutting speed and higher feed rate
In principle, at least three teeth should be in the material at all times when cutting to enable clean work. The blade diameter should therefore be selected depending on the workpiece and its size.
Finding the right circular saw blade
Four characteristics play a key role in selecting the right circular saw blade. The number and type of teeth, the cutting width and the speed of the blade are also important.
The type of teeth is decisive for the cutting quality and durability of the circular saw blade. The most common tooth shape is the rectangular flat tooth, which is ideal for longitudinal cuts in softwood and hardwood.
Alternate teeth have an angled back. They are often used as universal saw blades because they are suitable for both longitudinal and crosscuts.
Trapezoidal flat teeth are very robust and suitable for hard materials because they are particularly resistant to foreign bodies.
Cutting width
The cutting width depends on the thickness of the saw blade and its teeth. The thinner the circular saw blade, the lower the speed should be set. There is an increased risk of accidents if the speed is too high and overheating occurs.
Speed
The cutting speed - i.e. the speed at which the saw blade moves back and forth - should not exceed 100 metres per second. The larger the circular saw blade, the lower the speed should be set. The material being processed also determines how high the speed should be set: Non-ferrous metal (NF metal) and plastic can be cut at up to 5,000 revolutions per minute and wood can be cut at up to 9,000 revolutions per minute.
How do you change a circular saw blade?
Basically, the saw blade must be fixed in place, the power supply disconnected and the fixing screw loosened. Then replace the blade and tighten the screw again. Special instructions can be found in the operating instructions for the respective device.
What to do if the hole in the blade is too large?
The standard size has a diameter of 30mm. If a blade of this size does not fit on the saw, reduction rings can be used. These reduce the size of the hole and make the circular saw blade compatible with the power tool.
How do you recognize blunt circular saw blades?
Signs of bluntness are slower sawing speed, discolouration due to overheating of cutting edges, increased noise and vibrations. You should react immediately to vibrations, as they are signs of an imbalance that can cause the circular saw blade to shatter. However, blunt saw blades do not have to be replaced immediately; they can be resharpened up to 10 times.
