A common question I get asked is why do I make my miter saw cuts in two passes instead of one? When making a wider cut at my miter saw I almost always score the top surface with a very shallow cut as I pull the saw to me, then plunge down at the near end of the work piece, then push through towards the fence to complete the cut. The reason for this is to get a smoother top surface after the cut. The blade can cut in two directions; as it enters the material and as it exits the material. Any time the blade is cutting as it exits the material you have a greater chance of the exit surface tearing out due to lack of material support. So by making a very shallow scoring cut on top as the saw is pulled back you are cutting into the material which results in a much cleaner cut. Then as the saw is plunged and the final through-cut is made the rest of the material is cut on the intake side of the blade as well.
The top scoring cut is technically considered a climb cut because the blade is cutting in a direction opposite of the travel of the tool. When making a climb cut on any tool you have the risk of a tool “climbing” where the tool want’s to grab instead of cut and increase the speed of travel, sometimes faster than what you are prepared for. A very shallow scoring cut decreases the risk of this happening but the possibility is still there. If you make a cut like this always make sure you have nothing in the path of the blade, you have the material firmly secured, and you are aware of the potential hazards that could happen.