How to Adjust a Miter Saw to Cut Perfect Angles
A miter saw is a necessary tool in the workshop if you do a lot of woodworking. The miter saw is sometimes referred to as a chop saw. This saw makes miter cuts and beveled cuts for making boxes and picture frames. But once in a while, the miter saw needs calibrated to keep those cuts accurate. I’m going to tell you how to adjust your miter saw to make perfect cuts.
Even a brand-new miter saw can be slightly out of alignment with the markings on the detent plate. The detent plate is the metal plate that is towards the front of the saw that has the angle numbers on it. In some cases, the angle markings on the head of the miter saw may need fine-tuning as well so you can cut accurate bevels. You can easily adjust any miter saw to cut perfect angles every time. All you need is an accurate angle gauge or combination square, a screwdriver, and possibly a wrench.
There are many different brands of miter saws on the market. You may have to do things a tad bit differently to adjust your miter saw to cut perfect angles. However, the concept for adjusting all of the various miter saws is the same. You should be able to use this knowledge to keep your miter saw cutting perfectly.
Before we go any further, if you are new to woodworking, there is one important thing we need to discuss. Never work with any power tools without appropriate safety measures. Unplug the tools that you are fixing, repairing, or adjusting. Always wear safety glasses so debris or dust does not fly into your eyes. It is also necessary to wear a mask when you are working with wood because the sawdust particles are small enough that they can enter your lungs if you happen to inhale them. Do not wear work gloves when using saws or other cutting tools. Use them only to handle your wood.
For the Beginning Woodworker:
You may already know this, but it is worth repeating. When you mark an angle on the board that you want to cut, always position the blade so it cuts just on the outside of the line. For example, if you are cutting a 45-degree angle 3-inches from the right end of the board, you would draw a pencil or chalk line where you want the cut. If you cut directly on the center of that line, you will take off the width of the blade from your wood piece. This means that your measurements will be slightly short on that board. If you are using that same technique to cut three more pieces of wood so you can make a picture frame, two things can happen. Either the frame will be too small and/or the angles won’t join up properly and there could be gaps at the joints. Always remember to cut AFTER the cut line so your measurements are accurate. This, sometimes, is the reason projects turn out different than expected.
**These next steps can be done in no particular order.
However, I find checking the blade, the detent plate, and then the fence works best for me.
The first step to take when you adjust a miter saw to cut perfect angles is making sure your blade is not the problem. An old blade can get warped or damaged over time. The teeth may also be worn and not cut as accurately as they did when it was new. Use an angle square to make sure the blade is square with the base plate. Simply hold one side of the square against the side of the blade and the other straight edge on the base. There should be no gaps between the blade and the angle square. If you see a gap, you need to adjust your blade position. You will find the blade gauge toward the bottom at the back of the saw. Make sure the gauge is set to zero. If it is, then you may need to adjust the fence on one side or the other so the blade is at an exact 90-degree angle to the fence.
Check the base plate to make sure it is completely flat and there are no raised edges. If the flat board rocks on the base plate, your cut could be off. You need to fix the base plate of the miter saw so you get perfect cuts. To fix the issue, watch where the center point is of the board as it rocks. This will be the high spot that you must file down on the base to make it flat. Rough grit sandpaper wrapped around a sturdy piece of wood should work to file the spot flat. Always apply steady, even pressure so you ensure that when you are done, the entire base plate is even.
It is a good idea to check the fence guard to make sure it is at a perfect 90 degree-angle to the blade. Do this using your angle square as I described above. There are two Allen screws or bolts holding the fence securely in place. If there is a gap between the angle square and the saw blade, loosen the screw on the fence and tap the backside of the fence just until the gap is gone. Tighten the screw back, but don’t over-tighten or you risk moving the fence out of alignment again.
Checking the Angles
Check for proper 90-degree angle cuts. Set the miter saw up to cut a 90-degree angle. Make the cut and check the cut with metal or angle square. If the cut is exactly 90-degrees, all the other angle cuts should be accurate. Make a 45-degree cut and check that it is accurate. If both cuts are accurate then you do not need to adjust your miter saw because it is making perfect cuts.
The detent plate is the section on the front of the miter saw that tells you where to swivel your saw to make an angled cut. The angles go from 0-degrees (90 -degree angle) all the way over to 45 degrees. My detent plate is embedded onto the body of my miter saw.
There are some detent plates that are adjustable and held into place by several screws. If everything else on your miter saw is perfectly square, but the angle cuts are not accurate, your detent plate may be off. The best way to fix this problem is to determine how far off your cuts are and move the detent plate to account for the difference. For instance, if you cut a 45-degree angle but it is 5-degrees off, you need to loosen the detent plate and set it so the 5-mark sits where the 0-mark was. Then firmly fasten the detent plate down to the base plate. You may prefer to replace the detent plate with a new one if the one on your miter saw is bent or not reading accurately.
If you do not have an adjustable detent plate, you must adjust the miter saw manually to make perfect cuts. This means that if you want to make a 30-degree cut but the miter saw cuts the angle at 34-degrees, then you must set the angle to 26-degrees. If it is cutting at 26-degrees, then you need to set the blade at a 34-degree angle.
I hope this helps you adjust your miter saw to cut perfect angles for your wood projects.