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A miter saw is one of the most reliable electric saw cutters for making even cuts on wood. It is easy to use and safer than a table saw. It also takes minimal effort to make clean cuts with a miter saw.
However, sometimes a miter saw can cut unevenly and leave jagged edges and tear-outs on your wood. This can be frustrating especially when it happens on the wood you want to use to make some fancy furniture. And it begs the question, what can you do to prevent miter saw tearout?
Because I don’t want you to pluck all your hair as you try to find out why your miter saw splinters wood, I have summarized 11 potential causes of miter saw tear outs and how to fix them.
What causes miter saw tearout and how to prevent it
1. You don’t sever wood fibers before cutting
Some have no idea that a utility knife can be the difference between making a clean or a rugged woodcut on a miter saw. Yeah, if you score the cutline on the wood with a sharp utility knife you can prevent wood fibers from splintering. This is called severing the wood fibers.
All you need is a nice straight edge to guide your knife. Once you score the line on the face and edges of the board, the blade will not attempt to lift up wood fibers on its way out since they will be severed already. This will prevent splintering.
The caveat, however, is that you must line up the side edges of the saw blade teeth with the cut mark. Also, the kerf of the blade should be on the waste side of the board. The waste side is the side of the stock you will discard.
Cutting on the waste side ensures that you end up with the correct length of the board and that the edge is as smooth as you need it.
2. You are cutting with the finish side down
Unlike a table saw blade that cuts stock from the bottom, a miter saw cuts from the top. This means that the teeth of the miter saw blade must face down to make the tool safe and to avoid injuries. As such, if you are keen you will notice that tearouts on the miter saw occur at the bottom of the stock as the blade exits. And this somehow answers the question of whether you should cut wood on a miter saw with the finish side up or down.
If you guessed properly, you should cut wood with the finish side up on a miter saw. This will ensure that any splintering occurs on the non-show face. But if you need a clean cut on both sides, use a backer board underneath.
Sometimes though, splinters can occur on the top side. To prevent this from happening, you can tape the cut line. That way, you will be sure that the fibers are supported and you will not have to worry about splintering on the show face. Unless your miter saw blade is bad or not the right one.
3. You are using a blade with low tooth count
Another reason why your wood splinters on the miter saw is if you are using a blade with a low tooth count. Saw blades with low TPI cut fast but roughly. They are great for ripping wood.
So, if you want the edge of your wood to be as smooth as glass, go for a blade with a high tooth count. A good trim blade with at least 90 teeth or more will do a fine job.
However, more teeth mean you will cut more slowly. And this takes us to the next point.
4. You are pushing the stock too hard
Since blades with higher tooth count cut slowly, you need to be patient with the saw. Do not push the stock too hard. Just push it lightly and let the saw blade do the cutting. In other words, take your time and let the blade have time to do a better job. Slow down and get a 100-tooth blade for trim work
5. You are cutting with low-quality saw blade
The blade on your miter saw might have the right tooth count but poor quality. For example, stock blades that come with the miter saw are often low quality and mostly for general purpose use, not for finish work.
For this reason, you need a high-quality finish cuts blade. You can try the Diablo ultimate polished finish blade or use any blade from a reputable brand that has carbide teeth. And remember, even if you use a high-quality blade, it should have many teeth to produce a smooth cut.
6. You are not using a zero clearance plate or using the stock plate
If you are using the zero clearance insert that came with the miter saw or not using one at all, that could be the problem. You need to replace it with a custom insert.
A custom zero clearance insert has a narrower slot and therefore supports wood fibers better to prevent fraying or splintering. It is one of the most important jigs even on a table saw. So, just replace the stock insert with a custom insert and you will see the difference. You can buy or make one yourself.
7. You are not using a sacrificial board
For the miter saw to cut cleanly, you also need to “sacrifice something”. Not like you have to kill an animal and pour the blood in libation. No! I mean you have to put a sacrificial board underneath the stock you are cutting so that it is the last thing the blade cuts as it exits, not the stock.
A sacrificial board supports the fibers of your stock and keeps them from splintering. And if there is any tear out, it will occur on the board underneath, not your precious workpiece.
8. You are forcing the blade to cut in one go.
As I said, when you want a clean cut, you must be patient with the blade. This not only means pushing the blade slowly and lightly but also trying multiple passes instead of trying to cut the whole thing in one cut.
9. Dust collector not doing its job
Check that the dust collector is doing its job so that dust does not accumulate on the mounting surface and cause the miter saw to cut badly. After every cut, always wipe off the dust before placing new stock. This enables the saw to slide smoothly and the blade to run true.
10. You don’t wait for the blade to stop spinning
After making the cut, wait for the blade to stop spinning before removing it from the board. If you remove it while it is spinning, it could lift up some wood fibers on the edge and cause tearout.
Another important thing about the spinning of the blade is that you should always let it attain maximum speed before bringing it down to cut. Similarly, if you are using a sliding miter, let the blade spin at full speed before sliding it forward onto the stock.
11. The wood is the problem
Lastly, some, wood just doesn’t cut nice. So, if you have checked everything on the miter saw and it is good but the cuts are still rough, the problem could be the wood you are cutting. To be sure though, try to cut a different type of wood and see if the edge will be any smoother. If the edge is splinter-free, then you know the stock you are cutting is not that great and you need to change or fix it.
Well, those are the common issues that may be causing your miter saw to cut badly and how to fix them. If the problem persists, you may need to call an expert to help you troubleshoot. But if you are new to miter saw, you may be needing a bit of practice to learn how to use it more effectively.
I hope this information helps you make better and cleaner cuts on your miter saw.