A short time ago, I made a video to see if using a Zero Clearance Insert in a table saw would give cleaner cuts with less tear out than a non-zero clearance insert. The results that I came up with using double sided melamine doing this test, was clear that making and using zero clearance inserts made no difference to the quality of the cuts. That test used double sided melamine as the cutting medium and many people wondered if there would be a difference if I ran the same test, but this time using natural wood or even plywood. I was not sure if the results would be different, but I suspected they would be very similar to the melamine tests, but that was a guess and the only real way of knowing is to run the test.
Watch it on Youtube: https://youtu.be/38pU_LVtfb4
I decided to use three different kinds of wood for this test, Oak, Pine and a good, cabinet quality 3/4" plywood. I would to both a ripping and a cross-cutting test on all these wood with both zero clearance and non-zero clearance throat plates then compare the differences ...
As it turned out, this test was a LOT of work and a lot of blace changing and insert changing and to ensure I didn't get mixed up with what I was doing I marked every piece of wood with a red line on the top side of the wood .. that is the part that would be face up on the table saw, then I also wrote down what I would be doing on paper so that I could keep track of the process and as well, I marked each piece or wood right after it was cut, before moving on to the next piece.
I used the same blades that were used in the previous testing so that there would be some continuity. The ripping blades used were the Freud Glue Line Rip (GLR) the Freud 14 tooth thin kerf ripping blade, Freud 50 tooth combination blade and finally a no-name 40 tooth combination blade that came with my table saw. The Crosscutting blades were the Freud 90 thin kerf tooth, the Freud thin kerf 60 teeth with anti-kickback teeth, the same 50 tooth thin kerf as used in the ripping test, and the same 40 tooth no-name combination blade as used in the ripping test.
The process was to start off with a best quality ripping blade the work downward to the poorest quality ripping blade and make one cut each on Oak, Pine, and Plywood with non-zero clearance, mark the cuts then make the next cut with the same blade but this time with zero clearance insert.
The process for cross-cutting was the same, start off with the best quality blade and work down, making the first cut on non-zero clearance insert on each of the three pieces of wood, then make the second cut with a zero clearance insert with the same blade on the same three pieces of wood.
The pictures show clearly that just as with the double-sided melamine, using a zero clearance insert does NOT give a cleaner cut with reduced tear out. There is no perceptible difference on natural wood or plywood between a zero clearance and a non-zero clearance throat plate.
And for further proof, scroll down to the plywood crosscut picture which shows the most amount of tear out with the 40 tooth blade at in the bottom cuts, and compare that with the Freud 90 tooth blade at the top of the same picture.
If a zero clearance throat plate really worked, then the 40 tooth blade should have reduced tear out that should be at least similar to what the Freud 90 tooth performed, but it is not, it shows massive tear out even with a zero clearance insert.
Here are the pictures of the results.
Zero Clearance Table Saw Insert Test OAK
Zero Clearance Table Saw Insert Test OAK CROSSCUT
Zero Clearance Table Saw Insert Test PINE
Zero Clearance Table Saw Insert Test PINE CROSSCUT
Zero Clearance Table Saw Insert Test PLYWOOD
Zero Clearance Table Saw Insert Test PLYWOOD CROSSCUT
