Tuning Up Your Mitersaw
If you're still using the contractor-grade blade that came with the saw, my first advice is to upgrade to one more suited to woodworking. Choose a blade with a negative hook angle to prevent climbing during a cut. For a 10" blade, get one with 60-80 teeth; for a 12" blade, 80-100 teeth. These high tooth counts provide splinter-free edges when mitering and crosscutting.
Now, work the angles
Next, make sure that your new blade sits 90° to the base of the saw. Rest the handle of a quality square on the saw base with the blade of the square against the saw-blade body, not the teeth, as shown in photo. Your manual will explain how to adjust and set the stops on the saw's bevel post to eliminate any gap between the saw blade and the square.
Set the bevel
You can then set the cursor at the back of the saw to exactly 0°. Repeat this procedure to set the 45° bevel.
Square the fence to the blade
Once the bevels have been set, adjust the saw's miter stops. First, set the blade 90° to the fence, as shown in photo. Making this adjustment depends on the type of fence you have.
Adjusting a one-piece fence
For a one-piece fence, photo below, loosen the adjusting bolts or screws on each side of the fence and adjust either the right or left side to the blade body. You only have to adjust one side because this automatically sets the opposite side.
Adjusting a two-piece independent fence
If your saw has separate (left and right) fences, aligning each side square to the blade may result in fences that do not align with one another. The solution is to square one fence to the blade and retighten that fence's bolts or screws. Then, align the opposite fence, as shown in photo. Finally, adjust the cursor to 0°.
Adjusting a fixed fence
On some saws, the fences are not adjustable, as shown in photo, so you instead align the blade and saw carriage square to the fence. Do this by setting the miter at the 0° detent and then loosening the screws on the miter detent plate. Rotate the table (and the detent plate) to position the blade 90° to the fence. Then, retighten the adjustment screws. There is no need to adjust any other miter settings.
How did you do?
The true test of your work is to cut 45° miters on each end of four equal-length pieces of stock and check the fit by dry-clamping them into a square, right. A less-than-perfect joint at any corner means you'll need to review each alignment step and correct as necessary. Remember, miters draw the eye. With careful setup, yours will draw many admiring looks!