Introduction: Tune Up Your Table Saw With a 2x4
Getting accuracy and performance out of your table saw is dependent on how well you have it tuned and calibrated. Fortunately, a wealth of information exists on this topic. Unfortunately, many of those guides have you use expensive jigs, fixtures, and measuring tools to make your saw cut square and true. While this is very nice and quite precise, it's overkill for many of us. The truth is that no matter how well your saw is adjusted, if anything is out of alignment you'll be able to tell from the pieces that you cut and how they fit together.
This guide will show you how to use a 2x4 and a basic understanding of simple geometry to dial in your table saw.
Step 1: Understanding the Geometry of a Saw
Before we start making adjustments, it is important that you understand the geometry of what makes a good saw work well. There are 5 primary alignments and dimensions that need to be taken into consideration.
Table to Blade Alignment: When viewed from above, the miter slots in your table need to be perfectly parallel with the blade so that you can push a piece of wood straight through the saw without catching and binding on the width of the blade. If this adjustment is off and your blade is canted, you'll notice arcs from the blade's teeth scratched into the surface of your cuts.
Rip Fence Alignment: Your fence needs to be parallel with the miter slots and blade so that the pieces you rip against it are a consistent width and don't wiggle or bind against the blade. Inaccuracies in this adjustment can cause binds and kickback. You do not want to encounter either of these failures EVER, they're unpredictable and dangerous!
Miter Gauge Angle: The pointer on your miter gauge should read accurately so that you can precisely cut at any angle that you want. Most of the time you'll want a 90 degree miter angle so that the pieces you crosscut will have square corners.
Blade Bevel Angle: When you look across your saw from front to back, it's important for the blade to raise through the table at the proper angle. Most of the time, you'll want the blade to be exactly 90 degrees from the table, but certain jobs will require other bevel angles. Most saws have 'stop' points built in at 90 degrees and at 45 degrees. Making your indicator needle and stop points accurate will be critical to the consistency of your cuts.
Rip Scale (cut width) Indicator: You want the measuring tape on your guide rails to reflect the exact position of the rip fence and accurately show the width of the piece that you'll be cutting.
Step 2: Clean Everything - You Don't Want to Measure Dirt
First, you'll want to clean your saw. If you have dirt and grime built up, it can effect your measurements and calibrations. Take the time now to remove all of those globs and deposits so that your tune up can be as effective as possible. Clean, shiny metal is your goal.
- The table should be rust free and clear of chips and debris.
- Blow the sawdust out of your saw (don't forget the inside) and wipe down the motor, belts, and pulleys.
- Your blade should spin freely and have no wobble.
- You want the lead-screws that adjust blade height and bevel angle to turn smoothly.
A table saw is a very dangerous tool. People can and do encounter serious danger and injury while using them. I know people who are missing fingers because of a table saw - it's no joke. When you are not cutting a piece of wood, always have the saw unplugged and 'locked out' for safety - especially if you are working on the saw and will have your hands all over the moving parts.
My saw has a lockout tab on the power switch, I pull the plug out of the wall AND remove the lockout tab so that I have two layers of protection in case of human error.
One more note: Always use a guard over your blade. I removed mine briefly for pictures and measurement. A table saw is dangerous to operate without one.
Step 3: Measure the Blade to Table Alignment
Cut off a small chunk of 2x4, and run a drywall screw into the end of it. You want the screw to be close to one of the shorter edges of the board.
Pick a clean tooth on your blade and mark it with an X.
Clamp the board with the screw against your miter gauge, and rotate the blade so that the screw is just touching the tooth that you marked earlier.
You want the marked tooth to just slightly graze the surface of the screw as you move the blade back and forth. If there's any pressure to speak of or an air gap between the tooth and screw, loosen your clamp and lightly tap the board back and forth until you get the perfect tolerance. I find that a screwdriver handle makes a nice tool for tapping and nudging fine adjustments like this.
After getting the tooth lined up perfectly in front, slide the miter gauge back and turn the blade so that the same screw and X marked tooth align on the back side of the blade. You want to see the exact same tolerance here; the front should match the back.
If the tolerance is different between the front and back of the blade, you need to make an adjustment. On most contractor grade saws, the blade is mounted on trunnions beneath the table that can be loosened and adjusted for the perfect alignment. Cabinet style saws generally have fixed trunnions and require adjusting the table... This exact procedure will vary by model and manufacturer, so it's best to consult your saw's original owner's manual for more details.
Step 4: Align Your Fence With the Miter Slots
After your table and blade are precisely aligned, you'll want to make your rip fence parallel to them. The easiest way to do this is to move the fence just above one of the miter slots and to eyeball the resultant gap. You want it to be even and parallel all the way from front to back.
If there's any variation in this gap, you need to adjust it out of your fence. My saw has two bolts on top of the fence that you can loosen, realign, and tighten to change the fence angle. Your saw may be different, so once again, check your owner's manual for the exact procedure for your saw.
Another way to check this alignment is to cut two slices of wood that fit snugly in the miter slots and to slide the fence up against them to check for gaps. You can even do this with a feeler gauge, if that's the level of accuracy that you are aiming for.
Step 5: Check Your Miter Gauge
Adjust your miter gauge so that the pointer is perfectly on 0, indicating that it's perpendicular (90 degrees) to the blade.
Next, mark a piece of 2x4 with an A and a B so that one letter will be on each side of the crosscut that you'll make next.
After the cut, you should have two pieces just like this.
Flip over one of the pieces, so that one is facing up and the other is facing down.
Press both pieces flat against your miter gauge, and check for a gap in the seam between them. In this picture, you can see that there is a gap at the top. This indicates that the miter gauge needs to be adjusted slightly counter-clockwise to be at a perfect 90 degree angle with the blade.
Make your adjustment, and cut another piece to test the alignment. When you have everything just right, there will be no gap.
This works because two 90 degree angles form a straight 180 that you can compare against a known flat surface like the miter gauge. If your 90 degree cuts are inaccurate, laying the boards this way will double the inaccuracy and highlight the misalignment enough that you can see it. That, in a nutshell, is the magic that makes this whole calibration process work!
After you're satisfied with this adjustment, loosen the indicator needle on your gauge and adjust it so that it reads accurately.
Step 6: Check Your 90 Degree Bevel Stop
Next we will adjust your blade's bevel angle.
Most saws have a stop collar on the bevel angle lead-screw so that the blade can't travel beyond 90 degrees in one direction and it can't go past 45 in the other. Adjust your blade so that you're against the 90 degree stop and the blade is vertical.
Again, we're going to mark an A and a B on each side of the blade and crosscut a piece of 2x4.
Make the cut, and flip one of the pieces over, just like before.
This time, we'll be using the table top as the reference straight edge, and you want to look for a gap on the side of the pieces that you've just cut. This picture shows that the pieces are tight on bottom and have a gap at the top. The blade is tilted past 90 degrees and needs to rotate counterclockwise to be right on 90 again.
The 90 degree stop on my saw is a threaded collar with 2 brass set screws. To adjust it, I had to loosen both brass screws and thread the collar in and out until I found the sweet spot that gave me repeatable 90 degree cuts. Don't forget to tighten the set screws between adjustments, and once again after you're finished just in case.
A perfect 90 degree bevel will yield cuts with no gap. After you get this dialed in, you should adjust your pointer so that it reads accurately.
Step 7: Check Your 45 Degree Bevel Stop
Next, rotate your blade against the 45 degree bevel stop.
Before we continue with this step, a note about safety and bevel cuts: never crosscut a board with your miter gauge under the bevel angle (to the left on most saws). If anything slips, the wood will bind and be pulled under the blade, which is the last place that you want your miter gauge or heaven forbid, your hand, to be.
Once your blade is positioned at 45 degrees, and your miter gauge is on the safe side of the blade, you can make your first cut. This time, we need to cut 4 pieces to have angles that add up to 180 degrees.
Note that this image is just to show you the pattern that the pieces fit in, it is not the orientation that we'll set them in for measuring.
Once you've made all of the cuts, use the table top as your reference for flat. Assemble all 4 pieces, and press them against the table to check for gaps.
The above image shows a gap caused by the blade being tilted beyond 45 degrees. To make a perfect 45 cut, the blade needs to rotate clockwise, and the bevel stop for 45 degrees should also be adjusted. Just like before, repeat this process until you achieve a perfect angle with no gaps.
Step 8: Adjust Your Rip Scale Indicator
Set your rip fence so that it's just less than the width of a 2x4 from the blade. Lock the fence in place, and rip the board using a push-stick. Move the fence about 1/4" closer to the blade, and rip the other side of the board. The goal is to end up with a board that has sharp, square corners instead of the radius that 2x4's have from the saw mill.
This will make it much easier to see where the edge of the board hits the graduations on the measuring tape.
With the fence still locked from the second cut, you can set your newly ripped board over the fence's scale to see how accurate the cut was. Align the left side of your piece right on the 0 mark, and keep it there. Then, look to see if the horse-hair on the fence lines up with the right edge of the board or not.
You can loosen the screw on the viewing window and slide it back and forth to adjust the measurement that your fence reads.
Repeat this process until the board that you cut lines up perfectly at both ends of the scale.
Step 9: Other Handy Tweaks and Adjustments
Now that you've got the main things crossed off the list, here are a few other tips that will help you get things cutting like butter.
- Make sure that your table extensions are flat with the rest of the table top.
- Level your saw so that gravity doesn't make your boards wander 'downhill' as you cut.
- Adjust your fence to be an even height above the table.
- If you have blade wobble, find out why. Something could be dirty, warped, bent, etc. Find it and fix it.
- Ensure that your belts and pulleys are turning in the same plane. You want everything inline.
- Use a product like Johnson's Paste Wax to seal and lubricate your table. It's also nice to lubricate your fence.
- Use tools and accessories that will make your life easier. Push sticks, feather-boards, blade changers, blade stabilizers, etc will all make your table saw experience safer and easier.
Most of all, be safe and enjoy your table saw!
Thank you for reading, I'll see you in the comments section!