Sawdust on the Floor

It must be very frustrating being a tool manufacturer.  As woodworkers, we demand that our tools perform flawlessly each and every time we use them. We also demand that in all but some very rare cases that the tool be capable of doing more than one task.  You wouldn’t be very happy with your tablesaw or miter saw if it were only capable of making cuts at a pure 90° angle. Nope, we expect that these tools not only make these cuts, but in the case of the miter saw, we demand that it also makes beveled and compound miter cuts, our tablesaws are expected to not only perform rip cuts, but cross cuts and beveled cuts. At the same time, we also demand that the cuts made by these tools be smooth and have no tear out. And in a weird way, it’s this demand that the tools in our shop do more than one task that has helped to create problems like tear out. But not totally. Tear out is really a two part problem.

Here is the first part of the problem.  Wood is basically a series of fibers stuck together.  These fibers run in the direction of the grain of the wood.   When you rip a piece of wood, you are slicing these fibers along their length and tear out is not a problem. However when you cross cut a piece of stock, you are cutting the ends of these fibers. These fibers have very little strength on their own, they rely on the next set fibers for support. For example imagine cross cutting a 2″ wide piece of 4/4 oak. As the blade cuts the first fiber, it is held in place by the next fiber.  This mutual support continues until you have cut almost through the stock.  As the last fibers are cut, there is nothing to support them.  These fibers will normally tear rather than be cut.  This produces tear out.  The sad part is that there is very little we can do about this, wood is simply wood.  And we can’t change the makeup of it no matter how hard we try.

The second part of the issue involves some good old trigonometry. At all points of the blade other than when it’s at true 90°, the height and angle of the blade will form a triangle, the base of this triangle is the top of the tablesaw or miter saw.  The length of this base changes, depending on the height and angle of the blade.  To accommodate this fact, the manufacturers of our tablesaw saw and miter saws have shipped the saws with inserts wide enough to allow the blade to be tilted to its limits and the blade at full height.  This wide open insert is the second part of the tear out issue. This wide opening in stock inserts does not provide adequate support for the end fibers, creating a breeding ground for tear out.

Rather than complain to the manufacturers of our tablesaws and miters saws, a better solution would be to simply replace the stock insert with a zero clearance insert.  These Phenolic Resin inserts are offered for many different brands of tablesaws.  The idea is to remove the stock insert, don’t discard it, you will need it when you do any work not at 90°, and replace it with an insert that is sized for the blade you are using.  If you typically use blades with different kerfs, then it is recommended that you have inserts for each blade. 

To install, first raise the blade to its highest position.  Verify that the blade is really at 90°.  I would recommend that you use a good digital protractor for this task.  If the blade is not at 90°, refer to your tablesaw manual to adjust the zero stops of your particular saw.  Once you are satisfied that you are really at 90°. then completely lower the blade. Now remove and store away the original insert, and replace it with the Zero Clearance insert.  When you get the Zero Clearance insert, it will not have any opening for your blade. We take care of that next. 

The next step is for you to SLOWLY raise the spinning blade, so that it cuts a clearance channel in the Zero Clearance insert.   I have found that using the rip fence to hold one edge of the insert, and push sticks for the other edge works quite well.  Just be patient, don’t rush to get the blade to its final height.   Some woodworkers, who feel that the Zero Clearance insert is important enough, and that they cannot tolerate any tear out, will have inserts for not only different kerfs but for difference ranges of blade height.

It’s important that you only use this insert for work at 90°, as soon as you try to use it for a beveled cut, you will either bind the blade or deform the Zero Clearance insert.  Use the stock insert for all of these cases.

If your tablesaw is one of the major brands, or you like to do it yourself, there is a Zero Clearance insert  kit available that contains parts and tools needed to make your own inserts.  Simply use your original insert as the template for the outer shape of the insert. Use a 2 flute flush trim bit in your router or shaper to create a perfectly matched insert.  

The same problem occurs on our compound miter saws. The wide mouthed insert on most compound miter saws, just doesn’t provide the needed support for those wood fibers as we cut through the stock.  I haven’t located any aftermarket inserts for the compound miter saw yet.  But trust that I am looking.  In the mean time, when I absolutely have to prevent tear out, I will normally place a sacrificial piece beneath the stock piece I want to cut. 

So to the manufacturers, thanks for all of the options that your tools provide.  I just wished you could read the minds of all of the woodworkers, craftsperson’s and trades people who use your tools and provide us with that perfect tool that meets ALL of our needs at the same time.  Oh yeah, keep the price down at the same time.  Is that too much to ask for?

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