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Aligning a Table Saw

A poorly adjusted table saw is not only a source of endless frustration, it's also just plain dangerous. If the blade isn't adjusted to the miter slots, the saw can kick back while doing crosscuts, and if the fence isn't aligned with the blade, it can kick back while doing rip cuts. Either scenario isn't pretty. Also, the accuracy of your tools translates directly to accuracy in your work.

The Tools

The only truly effective way to align a table saw is to use a dial indicator. You need a stable platform to mount the dial indicator on, and that platform must ride in the miter slot of the saw such that it has no slop whatsoever. If you have more money than creativity, you can buy a ready-made alignment tool such as Ed Bennett's TS-Aligner. Being a member of the other camp, I decided to make my own jig:

The body of the jig is just a block of MDF or stable wood. An arm is attached to the block with a screw, and a dial indicator is attached to the end of the arm. The arm can hold the indicator horizontally or vertically, and has a series of holes that allows you to adjust the distance from the tip of the indicator to the miter slot.

The blue lines represent the miter slot on the saw, under the alignment jig. Attached to the underside of the jig are two large cheese-head screws (red circles) that register the jig against one side of the miter slot. The slop is removed by large pulley key (red crescent) that pivots on a small screw (green dot) and acts like a cam. The cam is pulled by a kevlar thread (cyan line) that goes up through a hole in the jig (yellow dot) and is tensioned by a spring (fat cyan line) on the top of the jig.

Here are a few pictures of the finished jig in use:

• Top view
• Bottom view
• Aligning the blade
• Aligning the fence

To use the jig, you stretch the spring with your hand and drop the jig into the miter slot. Releasing the spring pulls the cam against one side of the slot, pressing the two screw heads against the other side of the slot. That gives you three points of contact, under tension, and ensures that even as you slide the jig along the miter slot, you have a consistent measurement.

You also need an accurate combination square, but a small double square can also be helpful.

The Process

Okay, so you've bought, built or borrowed an alignment tool like the one I described above. The basic alignment process goes something like this:

1. Check the saw to ensure it's not hopelessly mis-aligned or in need of repair
2. Check your blade
3. Align the blade relative to the left miter slot
4. Align the fence relative to the blade
5. Align the splitter to the blade
6. Align the drive pulleys

Before proceeding, unplug the saw, remove the throat plate and the drive belt(s), remove the blade and raise the arbor to its highest position.

Step 1: Check the saw
The first thing you want to do is to make sure there are no non-adjustable aspects of the saw that will prevent you from completing the alignment. What good is it to try to align the fence to the blade if the blade wobbles? So, you want to check the following things using the dial indicator:

• Put the indicator in the left slot and the miter gauge in the right slot. Set up the indicator so the tip rests on the miter gauge body. By checking that the measurement is the same at the front, middle and back of the saw, you can measure the parallelism of the miter slots. If they diverge by more than a few thousandths, you may want to think twice before trying to use the miter gauge in the right slot. More on this later...
• Set up the indicator vertically so the tip rests on the arbor shaft. Rotate the arbor shaft by hand and note any movement in the indicator needle. A good saw will have very little vertical discrepancy on the arbor shaft. If it's more than a thousandth, you may have problems later on.
• Set up the indicator so the tip is touching the blade side of the arbor flange with the arbor raised to it's highest position. I did this with the indicator oriented at about 45 degrees. Again rotate the arbor by hand, noting any variation in the arbor flange. Any variation you see will be multiplied by the blade, so ideally you want to find that it's dead flat.
• Last, just grab ahold of the arbor shaft and try to wiggle it around. If you hear any clicking or feel any movement, your bearings might be shot.

Assuming that each of those checks showed very little or no discrepancy, all other adjustments can be made with confidence. Before proceeding, install your best blade in the saw.

Step 2: Check your blade
Using a warped blade causes all kinds of problems. Position the dial indicator so the tip rests on the saw plate just below the gullet. Rotate the blade by hand and watch the indicator needle. A variation of more than a few thousandths could be a problem. If you do see a variation, rotate the blade 1/4 turn on the arbor and re-check. Sometimes, if both your blade and arbor are mis-aligned, you can actually find a 'sweet spot' by strategically placing the blade on the arbor so that the variations cancel each other out.

Step 3: Align the blade
Next, you want to align the blade to the table. Typically, you align it relative to the left miter slot, because that's the slot in which most woodworkers use their miter gauge. Mark a single tooth on the blade with a tiny piece of masking tape. All measurements will be made to the blade plate under this tooth. That way, an accurate alignment can be achieved even if your blade is warped. Rotate the marked tooth to the front of the saw table and take an indicator reading at that point. Rotate the marked tooth to the back of the saw table and repeat the measurement. Any discrepancy at all needs to be fixed by adjusting the trunion mount points (contractor saw) or adjusting the saw table (cabinet saw). Refer to your saw's manual for details. Repeat the measurement and adjustment until the is absolutely no discrepancy. Take the time to get it perfect. Also take the time now to set the 90- and 45-degree tilt stops and the tilt angle indicator.

Step 4: Align the fence
If you found that the miter slots were perfectly parallel, you will want to align the fence relative to the right miter slot. This will allow you to align the fence with it in the area where it will actually be used. (This is good because not all fence rails are perfectly straight) If your miter slots are not perfectly parallel, you'll have to lower your blade and use the indicator in the left slot. Depending on your alignment jig, you may have to position the fence over the blade.

Whichever method you choose, just lock down the fence within reach of your indicator, and adjust the fence so a measurement taken at the front of the saw table exactly matches a measurement taken at the back. Now, some people will advise you to toe the fence out by 0.005" at the back of the table. This advice has started many a jihad, and is, in my opinion, very wrong and dangerous. My recommendation is to align the fence to be perfectly parallel with the blade. I don't care if you disagree, so don't try to convince me otherwise.

Step 5: Align the splitter
All saws come with a splitter, blade guard, or a combination of the two. In my opinion, you're just plain stupid if you don't use them. Again, I really don't care if you disagree. If you don't like the guard or splitter that came with your saw, there are plenty of aftermarket replacements that are better. The splitter does more than just hold the guard in place. It's main function is to keep the back of the blade (which is rising) from getting a good bite on the wood if you screw up while feeding stock through the blade. If the rising blade can't contact the stock, it can't throw it. (This is known as 'kickback') The physics are simple: A well-adjusted splitter almost eliminates the chance of kickback.

Okay, now that I got that off my chest, let's continue. Raise your blade and lay a good straightedge on the table so it is to the right of the blade and is touching two teeth, one at the front and one at the back. Align the splitter so that it is parallel with the right side of the blade and square to the table. It sometimes helps to clamp the splitter to a block of wood with two faces that are square with each other.

Step 6: Align the drive pulleys
If you have a contractor saw, it's important that you align the drive pulleys. Mis-aligned pulleys create a lot of vibration that can do some interesting things while your pushing wood through the blade. Don't just eyeball it, use a straightedge. If you don't have a straightedge that is long enough, run a thin board across your jointer. It's close enough. Also, if you have a contractor saw, I recommend you replace the stock 'V' belt with a PowerTwist link belt. They transfer power better, don't take a set like a standard belt, and don't vibrate as they spin. I saw a noticeable decrease in vibration and noise when I installed a link belt on my saw.

That's it!
If the non-adjustable measurements you took are in spec and you took the time to get all your adjustments perfect, you should be able to rip 8/4 cherry with no saw marks or burning, even if you pause for ten seconds halfway through the cut! Believe it -- I've done it on my Jet contractor saw. (Hint: I use a Forrest blade)