Ever gone to purchase a sawblade and wondered just what all the codes are engraved on the side (or printed on the packaging)?
There are a surprising number of variables that are possible with saw blades, so many versions that can be considered. Some are irrelevant when choosing between one blade and another – they distinguish between a blade suitable for wood vs plastic (for example). Some blades do cross over – the Flai Mustang for example, which will have variables that suit both materials.
For example: ATB D250, K3.0 B30, Z40, H10
ATB = alternating top bevel – this blade has its teeth set so it is like a chisel, with one tooth cutting to the left, and the next to the right of the kerf.
You could have 4+1 (4 ATB teeth, plus one FT (flat tooth) as a raker tooth, flattening the bottom of the cut). An ATB blade leaves a V groove in the bottom of a partial-depth cut, and the 4+1 is a way to resolve this, leaving a flat-bottomed kerf.
Other options include HATB (or HiATB), where the teeth are even more angled which is good for melamine, and timbers prone to tearout, TCG (triple chip grind, also known as triple cut, FT (Flat Top), HG (hollow ground)
D stands for diameter – size of the blade in mm. A 250 blade (or to be exact, a D254) blade is 10″
This is the kerf of the blade, measuring across the teeth. This does not mean the blade will actually cut a 3.0mm wide kerf however. Blades have runout (just how flat is the blade, and during use just how flat it remains as the temperature of the blade changes). Saws (tablesaws or circular saws) also have runout, and it is a combination of both that will dictate exactly how wide a kerf you will get. If you want to know it exactly each time, you have to measure it whenever you change blades. The next time you mount the same blade, it could be different depending on at what point of rotation that the saw is vs the blade. It is much easier just to do a test cut and remeasure if it is that important. This concept is greatly (and deliberately exasperated) for a wobble dado blade, which is designed with a large amount of runout which can be dialed in, creating a dado (or wide trench).
This is the size of the bore – the hole through the middle of the blade. Depending on your saw you can either get a blade that specifically matches your saw, or one that is larger and get some saw blade bushes (or reducers) to match both the blade and you particular saw. They are not as convenient (but are still easy to use), and they allow you to purchase blades that are suited to your needs without necessarily being made for the size bore you require. Of course, if the hole is smaller than your arbor, you have a problem! Getting back to dado blades for a sec, when using stacked dados, I would strongly recommend getting one where the bore is correct for your saw – there are enough things to juggle without also having to try and manage a bunch of bushes as well.
Z stands for the number of teeth. A ripping blade can have around at little as 24 teeth, a crosscut blade as many as 100.
H is the hook angle (or rake angle). Large hook angles are an aggressive blade, particularly for ripping soft timbers. Small, zero or even slightly negative for crosscutting hard timbers.
These are just some of the variables and codes that can be written (engraved) onto the blade. They may not all be listed, and some blades may list a whole bunch more. If you know these at least, you are well on your way of being able to distinguish between one blade and the next.
Some other variables include top clearance angle, top bevel angle, gullet size, gullet plug, expansion joints, noise reduction slots, max operation RPM, carbide type, base blade material, blade coating, body thickness and so on. We’ll stick with the most common concerns at this stage!