There are many things in woodworking that I have experimented with or tried out, some worked and some did not. I always enjoy the challenges of learning new things and maybe even coming up with new processes and ways of working, but there is one thing that I have little interest in spending my time on and that is attempting to sharpen my own table saw or miter saw blades. 

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I purchase good quality saw blades for a reason, and that is to get good quality cuts in wood because when I do this so I don't have to spend my time fixing, repairing, and sanding out imperfections that lesser quality saw blades can create ...  

Sure I use inexpensive, or what I call "disposable" saw blades from time to time, but only for cutting through wood that may have nails, screws or gravel embedded in it, particularly like pallet wood, or some forms of recycled woods. I do not want to risk damaging one of my expensive saw blades in case there is a nail or screw that my metal detector did not pick up.

How To Tell When a Blade is Dull
Saw blades that are purchased new, are all very sharp, but in the coarse of cutting wood the carbide tips wear down, and more so on their edges. 
Carbide has the consistency that is similar to concrete. The wear that happens is minute chips of carbide that flake off and the more that flake off the duller the blade gets. 
As can be expected a blade that is used more and more will become more and more dull, so there are varying degrees of sharpness.
Some of the indicators of a dull blade might be.
 - It is harder to push the wood through the table saw than when the blade was new
 - the wood tends to "burn" more readily
 - there is a tendency for woods to "smoke" as they are being pushed through the blade
 - The saw cuts are "rougher" than when the saw blades were new

The best way to test how sharp a blade is to gently pinch the carbide tips between your thumb and forefinger and drawback. A new blade will tend to want to "grab" the skin on your fingers. A blade that is becoming dull, will slide more easily and not want to grab the skin, and the duller and duller it gets, it will slide more and more easily.

How is Carbide Sharpened
Carbide can only be sharpened with a diamond-encrusted abrasive tool such as a tiny router bit or some sort of a diamond blade. 
As a rule, a quality sharpening shop who can sharpen your saw blades to what the original factory specifications for that blade were would be using something like a 5,000 grit grinding bit that would fit in a specialized CNC - digital sharpening machine that also has a coolant running over the grinding process as it is sharpening. 

In a home-made DIY shop environment, the alternative for a diamond grinding wheel is a diamond-encrusted tile cutting blade that can be purchased a most hardware stores for around $25  and that will have a grit rating of between 180 to 220 grit - which makes sense because these blades are used for cutting through tile, not sharpening saw blades. 

This what a diamond blade on a tlle saw looks like

What Parts of each Carbide Tooth are Sharpened
In a quality sharpening shop, again, using a CNC - Digital sharpening machine, all the coordinates of a tooth are typed into the built-in computer of the sharpening machine. These coordinates are identical to the factory sharpening settings so that each tooth can be sharpened to the exact specifications as what was done at the factory.

With these readings fed into the sharpening machine, as a rule, all sides of each tooth are "polished" by the sharpening bit, including the face of the tooth, the "cheeks" of the tooth and top of the tooth. Like many things, there can be exceptions to what parts are sharpened depending on specs and what needs to be done.

In a home-based DIY shop, using a shop-made jig, as a rule the only part of the carbide that can be sharpened is the face, and the accuracy of how much "polishing" or grinding needs to be taken off each tooth is dependent on the operator and how much time and pressure is applied to the grinding process of each tooth. It is common that each tooth will have a varying degree of "grind" applied to it. This variation can result in differences in tooth length because only the face of the carbide is ground. In extreme cases, it can be shown that some blades will have one or a small number of teeth that are longer than the other teeth so the shorter teeth will not even be cutting wood because the longer teeth will be doing all the work. 

Sharpen Table Saw Blades

Sharpen Table Saw Blades
Tooth angles can be very complex and in many cases, all sides need to be ground or "polished"

Is It Even Worth Sharpening Blades
That's an excellent question and not an easy one to answer. 
Saw blades come in many different forms .. Thin Kerf and Full Kerf, they come as few as 24 teeth and as many as 120  ( + / - )
Some more expensive blades are designed for special jobs and are designed specifically for what they do ... other blades as cheaply as possible and only to fill a place in the market place for people who want cheap saw blades. 
The inexpensive and often no-name blades, I call these disposable blades because they are seldom worth sharpening ... but a good quality sharpening shop will be able to tell you very quickly if a blade is worth sharpening or not.

Very often, a Full Kerf, commercial saw blade, like those used by commercial woodworking and cabinet shops, or by serious woodworkers who are producing quality products, will see the value in having their blades sharpened. What many of them do, is have a small suite of blades, some that are in being sharpened, while others are being used in the shop ... that way they are never out of production. 

If you have spent good money or good quality blades and you want to save a few dollars and bring them back to what they were like new, then a good quality sharpening shop can do that ... and by the way, they can also sharpen the blades for your jointer, planer, router bits and probably even your oscillating tool, but do yourself a favor and check a local sharpening firm to see if they can do the work you need done ... and if you are inclined, and you just want to see how the process works, go ahead and make your own sharpening set-up and one of your disposable blades and have some fun working on your own blades ...

Table Saw Blades

Copyright Colin Knecht

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