In this post we’re going to have a look at saw blades in a little bit more detail. This information will help you know what to look for when buying your next blade.
What makes a circular saw blade? The main parts are the Body, which is the piece of steel that is the blade itself, and the Teeth which are the small tips which cut through the material.
In order for the teeth to cut they need to be sharp, and in order for them to cut effectively and safely they need to be angled. This blog post is going to look into both of these aspects and help you know what to look for when you’re buying a new circular saw blade.
Almost all circular saw blades nowadays are classed as TCT Blades, with TCT standing for Tungsten Carbide Tipped. This means that brazed onto each steel tooth is a small tip made of carbide, and this is what performs the actual cutting.
In order for the carbide tip to cut it needs to be sharpened, and this is done by the process of grinding. The tips are ground differently for different materials, with the most common types of grind being:
ATB (Alternate Tooth Bevel) – This is used for cutting wood and features a bevel across the top of the tooth which is angled from the outside in. Each tooth’s bevel alternates between the left and right side. ATB grind is most popular for wood as it allows the user to Rip (cut along the grain) as well as Cross Cut (cut across the grain).
Triple Chip Grind – This grind is used for cutting soft metals such as aluminium, as well as plastics and laminate. It features two different grinds in alternating teeth, one tooth is ground flat, and the next tooth is ground as a trapeze. The Trapeze tooth cuts a groove into the material, and the flat tooth then comes and removes the sides left by the groove.
Special Bevel Sharpening – Specifically designed for cutting into hard metals such as steel this grind offers a mix of a Flat Top and an Alternate Beveled edge. This is not as aggressive as ATB grind so, coupled with a negative hook angle (which is explained further down), it allows you to cut into steel slowly without knocking the carbide tip off the blade.
If you are cutting wood then you want a blade with ATB grind, if you’re cutting aluminium or plastic you need Triple Chip Grind and if you are cutting steel then you need the Special Bevel Sharpening on your blade.
The Hook Angle (also known as Rake) is how far forward or backward the carbide tip is leaning. If it is angled forward this is known as a positive hook and backwards is a negative hook.
A positive hook is used for cutting wood, it gives an aggressive cut which pulls the material into the saw blade. The result of this is a fast cut but the finish isn’t as smooth as with a negative hook (however this can be counteracted by the number of teeth on the blade, with more teeth giving a smoother finish).
A negative hook is less aggressive which means it cuts slower, this is used for cutting tougher materials such as metals and plastics.
0° Hooks are applied to blades intended for use on Chop or Mitre Saws. With these machines you are bringing the blade down onto the wood and a positive hook can cause them to ‘self feed’ by pulling the wood up towards them, this is how fingers are lost!
0° or Negative Hook acts in the opposite way by pushing the wood down and against the machine’s fence, which adds a margin of safety.
If you’re cutting through wood with a hand held circular saw then look for a positive hook with an ATB grind, if you are using a chop or mitre saw then you will want a 0° hook, and if you’re cutting metal then you need to have a negative hook with either Triple Chip Grind or a Special Bevel Grind.
The Walker Tools range of circular saw blades includes blades for use in all different machines and for cutting through different materials. The Walker printing on the front of the blade will clearly tell you the machine it is intended for, the hook, the grind and the material it is designed to cut, making it easier for you to select the correct blade and get the best results.