If you recently purchased a new or used table saw, or you moved the table saw you have from one location to another, one of the first things you’re gonna wanna do before making any cuts is make sure the blade is perfectly aligned with the miter slots.
The reason for that is that if the blade is out of alignment it can cause excess friction and resistance, which can:
- Make it more difficult to push the workpiece through.
- Lead to burn marks.
- Kick the workpiece back at you.
So if you’re experiencing any of those problems, you need to check your blade’s alignment. But before doing it, let’s see what kind of tools you need to accurately align the blade of your table saw.
Blade Alignment Tools
Since there are multiple ways to measure the blade’s alignment and to adjust it, you can use a lot of tools too. But I’ll list here only the blade alignment tools I use:
A square is a simple metal tool used to make marks square to an edge, as well as check the squareness of different faces/edges. You’ll need it to make your blade vertical on the table.
2. Combination Square
A combination square is an advanced square composed of a ruler and a squarehead affixed to it. You’ll need it to accurately measure the distances between the ends of the blade and the miter slot.
You can also use a combination square instead of the regular square, to check if the blade is perpendicular to the table.
3. Dial Indicator (Optional)
A dial indicator is an extremely accurate tool that can be used to measure the blade’s distance from the miter slot. But it’s not really necessary if you already have a combination square.
4. Magnetic Level Box (Optional)
A magnetic level box is an amazing tool any table saw user should have in his workshop. It’s very accurate and incredibly simple to use. Also, it will save you a lot of time when trying to make the blade square to the table.
5. Different Jigs (Optional)
If you don’t have a combination square, or a dial indicator, or a magnetic level box, then you should buy them! Okay, I may be kidding, but seriously, they are very useful in a workshop.
Anyway, if you don’t have any of them, you can always make a jig. There are many tutorials online for any type of jigs you might need and, honestly, only your imagination is the limit here.
Before I bought my level box, I used a simple jig made from a straight piece of wood with a screw at one end to measure the blade’s alignment. And the measurement process is the same as the one below, except that I’ll use the miter gauge to move the piece of wood from one end of the blade to another.
It really doesn’t matter what blade alignment tools you’re using as long as the result is the same: an almost perfectly aligned table saw blade.
How To Check If The Table Saw Blade Is Parallel?
The blade and motor are mounted to a couple of brackets called the trunnions. And this trunnion assembly, depending on the table saw you’re using, is either mounted to the table saw’s base, or to the underside of the table. So during manufactory or transportation, this assembly can get bumped or jarred slightly out of alignment.
Now, the blade’s alignment isn’t a thing we can necessarily see when we look at it. You need to measure it to determine if the table saw blade is out of alignment.
There are a number of ways you can test this alignment. But in general, you need to measure the distance between the front of the blade and the miter slot, and comparing it to the distance between the back of the blade and the same miter slot. If those two distances are equal, it means the blade is parallel to the miter slots.
Here’s how to check if the blade is parallel or not:
1. Unplug The Table Saw
This is the first thing you need to do, and the reasons are obvious. Unplug the table saw every time you’re making some changes or adjust the settings of the machine.
2. Raise The Blade To Its Full Height
In order to accurately measure the distance between the miter slot and the blade, you should raise the blade to its full height. Do this by rotating the wheel usually positioned at the base of the table saw.
3. Check If The Blade Is Square To The Table
You can easily do this with a square. Once the blade is raised to its full width, place the square with one side on the table and tilt the blade until the other side of the square touches the plate of the blade (not the teeth of the blade).
If the square is perfectly flat on the table and on the blade at the same time, then the blade is perpendicular to the table.
4. Remove The Table Insert
You need to remove the table insert around the blade to properly measure the distance from the blade to the miter slot.
5. Measure The Distance Between The Blade And The Miter Slot
I will use the combination square for this. Here’s how I do it:
- Place the combination square in the miter slot so it’s pressed tightly against the side that’s closer to the blade.
- Slide the combination square until it’s lined up with the front of the blade.
- Extend the ruler so that it just touches one of the teeth of the blade, and fix it. When you move the blade back and forth you should hear the tooth rubbing against the ruler.
- Mark that tooth with a marker.
- Rotate the blade around until the marked tooth is in the back of the blade.
- Slide the combination square until it gets aligned with the marked tooth. Make sure it remains pressed against the side of the miter slot that’s closer to the blade.
Now you can compare the front to the back distances. If the distances are not the same, then your blade is not aligned with the miter slots. So how do you make the table saw blade parallel?
How To Make The Blade Parallel?
Depending on the table saw you’re using, the way you can adjust the blade will vary. So you should refer to your own table saw’s manual.
In general, contractor saws, jobsite saws, or hybrid saws have the trunnions mounted to the underside of the table, while cabinet saws have the trunnion assembly mounted at the base of the table saw, inside the cabinet.
Since I’m using a cabinet saw, I’ll cover the way I make the blade parallel to the miter slots for a cabinet saw.
Here how to make the blade parallel:
1. Loosen Up The Table
All you need to do with a cabinet saw is to loosen up the table’s connection to the base and adjust the table to make the miter slots parallel to the blade.
Usually, the table is secured to the base with four bolts, one in each corner. So in order to shift the table to one side, you need to loosen up three of those four bolts and leave one tight to act as a pivot.
It all depends on where is your blade closer to the miter slot. For example, if the back of the blade is closer to the miter slot than the front of the blade, then you need to shift the table slightly to the right, leaving the lower left bolt tight.
Take a look over the below image to better visualize this process:
2. Tap The Table Into Alignment
Grab a dead blow hammer and slightly tap the corner of the table to bring it into alignment.
Then get the combination square and measure again the distances between the front and back of the blade and the miter slot. If they are equal, screw back the bolts and you’re done. If not, continue to tap the table with the hammer and measure again until the blade is in perfect alignment with the miter slots.
What About The Other Table Saws? How To Align The Blade For Those?
Now, if your table saw is not a cabinet type and the trunnions are mounted right under the table, you will make the blade parallel to the miter slots totally different. But the steps to check if the blade is parallel are the same.
For the cabinets, we moved the table to adjust the blade’s parallelism, but for the rest of the table saws, you don’t need to do this. They have an adjustment bolt that allows you to rotate the blade, instead of the table. It’s way much easier than for cabinet saws.
So if your blade is not aligned with the miter slots, you need to determine which direction the blade needs to rotate. Let’s take the same example as above where we aligned the cabinet’s blade.
If the back of the blade is closer to the miter slot than the front of the blade, then you need to shift the blade slightly counter-clockwise.
Now you need to locate the adjustment bolt. In general, you can find it inside the table insert opening, on the left side of the blade.
You will notice that you can’t simply adjust the bolt because there’s no room to use your hex key (Allen wrench). So you need to loosen the arbor nut and move the table saw blade slightly aside until you can insert the hex key a adjust the bolt.
Rotate the bolt in the direction you need until the blade looks aligned with the miter slots.
Slide the blade back into its original position and tighten the arbor nut. Then repeat the measurements to determine if the blade is perfectly aligned. If it’s not, repeat the process.
Believe me, it’s much easier to do when you have the table saw in front of you.
Once you have the blade aligned, you shouldn’t need to check it again unless you move the table saw, or there’s an impact on the table that might throw the blade back out of alignment.
Blade Alignment Tolerance
Now I saw online a lot of questions regarding the blade alignment tolerance. People noticed that the blade can’t be perfectly parallel with the miter slots. But this is fine. Really, it is!
If you use the combination square to bring the blade into alignment, you probably won’t meet this situation. But if you’re using a dial indicator, you might see a small difference between the two distances from the blade and the miter slot. That’s normal.
To calculate the blade alignment tolerance just subtract the distance between the front of the blade and the miter slot from the distance between the back of the blade and the miter slot. Or subtract whichever one is smaller from the bigger one.
A normal blade alignment tolerance should be equal to or less than two-thousandths of an inch (0.002″).
If your alignment tolerance is 0.003″ or higher, you can do better. If it’s 0.002″ or lower (0.001″, or 0.0009″) then you’re alignment isn’t noticeable.
Working with tolerances of thousandths of an inch (0.000″) is the most realistic scenario and what most of you will ever need for your table saw.
Working with tolerances of tens of thousandths of an inch (0.0000″) is an unrealistic scenario because it means to take into account the room temperature and the ground vibration when setting up the alignment of the table saw blade.
If you can get yours to zero tolerance, that’s amazing. But I doubt it will happen.
Just remember, a good combination square and a little experience with measuring are just enough to properly align a table saw blade.