i think pretty much everyone agrees that a table saw must be adjusted from time to time to ensure the blade is cutting straight most people know that but few i think really understand why you may think you do but based upon some of the debates that i see online a lot of people don't know what they don't know for example some say that your blade should be aligned with your fence but the truth is you should never use your table saw fence as a reference for aligning your table saw blade likewise some folks think that making a cross cut when your blade is angled to the side will produce a miter on the end of your board equal to that angle it's not true either so while you may know you should align your table saw you may not fully understand why it must be done and the effects that happen when you don't do it properly knowing the why can be both surprisingly interesting and it can help you identify and solve problems that you may have with your cuts later on here's a diagram of a saw where everything's properly aligned note how the blade and the fence are parallel to each other if a rip cut were made under these circumstances the kerf would be nice and straight and of equal width to the thickness of the blade but note what happens when you angle the back of the blade away from the rip fence it obviously can no longer follow that same straight narrow curve the front of the blade is still cutting in the same place but the back of the blade ends up in a different spot entirely the result will be a kerf that's wider than the blade is thick the front of the blade begins the cut then the sides of the teeth along the rest of the blade continue to shave away more material widening the kerf all the way to the back you may think that this won't matter much because all the material on the left side in this case is waste so who cares if we eat up a little more of it but you're making your saw work a lot harder you're making your blade work a lot harder and you're generating more heat which leads to more burns and blade marks you're also doing something else especially if the saw blade is raised up higher so the teeth in the middle towards the top of the arc are above the wood and no longer cutting in that case only the front and back teeth engage the wood so the front begins making its narrow curve but as the wood advances it encounters the smooth side of the blade which is unable to widen the curve the work piece will become difficult to hold against the fence as it tries to track with the blade of course a tightly satin sturdy rip fence will resist this turning motion and you're going to generate more friction and heat producing an inaccurate cut of poor quality if you're having trouble keeping your board against the fence as you make a rip cut your blade's probably misaligned things can get even worse if the back of the blade is angled toward the fence as shown here now the toothless body of the blade will push the board toward the fence rather than pulling it away from it this can create a wedging effect between the smooth side of the blade and the fence itself if the blade misalignment is great enough and the wedging effect strong enough that board can violently kick back toward you obviously these blade angles are exaggerations but anything more than a few thousandths of misalignment either toward the fence or away from it can make your rip cuts more difficult with more blade marks more burns less accurate and consistent in width and potentially more dangerous now what about cross cuts this is where i see the most confusion and misunderstanding as i said some people believe that a blade that's angled in relation to your miter gauge is the same as a miter gauge that's angled in relation to the blade but the two will produce different results when you angle the miter gauge itself you create an angled cut on the end of the work piece that's equal to the angle of the miter gauge's fence this is how things like picture frame corners are made but what if the blade itself is angled instead of the miter gauge the effect will not be a miter cut what will happen is something similar to what we saw with the rip fence but with a slightly different result here the cut line on my work piece is lined up with the front of the blade as it begins to cut you can already guess what's going to happen the blade will try to widen the kerf and compensate for that misalignment if the blade is set sufficiently low so the teeth at the top of the arc are still at least partially engaged they'll widen the kerf as before but either way the blade will also pull the work piece to the side in this case there's no fixed rip fence in the way to stop it so the effect will not just be a widening curve but also a shifting work piece that moves past your intended cut line this shift will be progressive it will pull to one side gradually as you advance forward the resulting end of your board won't be angled to match the misalignment of the blade but it won't likely be square either it'll probably be shorter than you intended to and it is certainly not going to be cut as crisply and cleanly as it should be the reason why a blade that's angled in relation to the miter gauge has a different effect than a miter gauge that's handled in relation to the blade is the path that miter gauge takes is locked into the miter slot on top of the saw those grooves in the cast iron are always straight forward and back they're not going to change naturally then it's those miter slots that set the standard for table saw alignment everything should reference off them if a saw blade is set parallel to the miter slot it will be parallel to the path of the miter gauge and your cross cuts then will be determined by the angle of your miter fence alone likewise if you set your rip fence parallel to your miter slot you'll know that it's also parallel to your blade everything references off the same place so everything works in harmony as a side note whenever i mention that the rip fence should be parallel to the miter slot and therefore to the blade i get some folks arguing that i'm wrong or stupid or inherently evil because everyone knows that the far end of a rip fence should be angled slightly away from the blade as a way to prevent kickback by being doubly sure that a board can't wedge between the fence and the blade well you could argue that i'm stupid but i'm not wrong most table saw manuals i've read say the fence should be parallel to the miter slot they're very clear about that but i think that other manuals particularly in europe maybe some in canada and elsewhere say something else this is just one of the many things we see differently another is the length of the fence we favor here in the united states the markings on our rulers the side of the road we drive on and how we pronounce aluminum we can argue the pros and cons of each of these things and we might in future videos but keep in mind that there are two sides to each issue 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