A miter saw is a useful workshop power tool for cross cuts, allowing them to be made easily and accurately. But sometimes, the saw doesn’t cut straight! What do you do next?
There are several reasons your miter saw may not be cutting straight.
- The fence and blade are misaligned
- The blade is warped, damaged, or not installed correctly.
- The bevel gauge on the miter saw is misaligned.
- The miter gauge is misaligned.
- The workpiece is not properly secured with a clamp for bevel cuts.
Some of the problems causing inaccuracy are easily remedied, while others may require some investigative work and realignment of the mechanisms in your miter saw. We discuss the four main reasons why your miter saw is not cutting straight and what you can do to restore the accuracy of the cut.
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The Primary Reasons Why You Miter Saw Is Not Cutting Straight
A miter saw may be useful, but it can be quite frustrating when your miter saw is not cutting the way it should.
Some of the reasons a miter saw doesn’t cut straight straight can be related to operator error, while other causes are related to problems with the saw itself.
The Fence and Blade are Misaligned
The very first thing you should do have pulling your miter saw out of the box and securing it to your workbench, is to check the alignment between the blade and the fence.
Unplug your saw, and place a speed square between the blade and fence like in the photo below. It should be perfectly aligned to both.
If these two things aren’t square, every single cut you make will be off.
Luckily, it’s usually an easy fix which is detailed in your user manual.
For my saw, I just need to adjust these screws in the back of the fence (there are more than just the one.)
The Miter Saw Blade Is Warped Or Damaged
Another possible cause of inaccuracies in the cut with a miter saw can be the result of problems with the blade itself.
If you have had your miter saw for some time and have been using the mounted blade for a long time, this may be the cause of the miter saw not cutting straight!
With long-term use, the blade is subjected to large fluctuations in temperature and exorbitant amounts of stress from the blade’s speed and the wood’s resistance.
Over time, this can cause the blade to warp and develop a wobble. If the wobble is severe enough, it can result in the cut on the workpiece being uneven and deviating from the cut line.
The only solution in this circumstance is to replace the blade with a new one. This will restore the accuracy of the cut for your miter saw.
Pro Tip: To check if the blade is warped, unplug the saw, shine a light on the side of the blade while you spin it by hand. If the blade is warped, you will see the inconsistency in the shadows on the blade as it turns.
Another possibility for new miter saw users involves the installation of the blade. If the blade has not been installed correctly, particularly not tightened sufficiently, there could be “play” in the blade as it spins, allowing it to wobble on the saw hub.
This will cause the blade to not spin true, resulting in inaccurate cuts. The solution to this is to re-install the blade correctly.
The Miter Saw Bevel Gauge is Misaligned
When the miter saw blade is angled to make the bevel cuts, you rely on the accuracy of the bevel gauge on the miter saw to give you the correct angle for the cut.
The alignment of the bevel gauge can be inaccurate due to the movement of the machine or if the miter saw has sustained an impact.
This is not only a possibility on an older, well-used saw, but the gauge can be inaccurate in a new machine out of the box. The gauge may be misaligned if the miter saw had a rough journey during its delivery to your workshop.
Most miter saws have a procedure detailed in the manual on how to realign the bevel gauge to restore accuracy in the angle of the cut. Since all saws are different, you will need to consult the user manual for your saw to establish the correct procedure for your miter saw.
The Miter Gauge Is Misaligned
In a similar way that the bevel gauge of your miter saw can become misaligned, the miter gauge can also suffer a similar fate, causing inaccuracies in these types of cuts with your saw.
This is most noticeable when you are making miter cuts to build frames that need to be square, such as picture frames, window frames, or other framing work.
If the miter gauge is not aligned properly, the angles of the cut will be off. When you assemble your project, this will produce problems; you will find you cannot get the frame square.
The solution is to realign the miter gauge to restore accuracy. The user manual that came with your miter saw should have instructions for performing this on your specific saw.
The Workpiece Is Not Clamped When Cutting Bevels
The most frequent complaint with miter saw users is that the saw is not cutting straight when making bevel cuts.
Much of this miter saw problem has to do with the dynamics of the saw and the physics involved during the bevel cut. When setting up the saw for the bevel cut, the head of the saw, the part holding the blade, is angled to the angle you need for the bevel.
As the saw is lowered to make the cut, the angle of the saw combined with the spin of the blade wants to draw the workpiece in towards the saw blade.
This can result in the workpiece shifting during the cut, and even small movements of the wood will result in inaccuracies, and the cut will not be straight and true.
The best way to prevent this problem during the bevel cut is to ensure the workpiece is securely clamped to the saw table.
You can clamp the piece to the back fence or to the base plate of the table using C claps, or if your saw comes with clamps for this purpose, use them.
While holding the wood in place with your free hand is a viable strategy with a normal cross cut, it doesn’t always work as well for a beveled cut.
The force with which the blade pulls the wood in is more than you can resist with your own strength.