Miter saw blade leaves some of its paint on the board

Question

When I crosscut a board on a miter saw, if I follow safety rules and let the blade fully stop before raising it after cut is done, it leaves some marks on the corner of the just-cut miter where the blade enters the wood. On the picture below it's top left corner:

These marks appears no matter if I hold the board by hand or use the clamp - no difference.

If I raise the blade immediately without releasing a trigger (i.e. rotating at full speed), which is not safe and should not be done, there is no marks left on the miter.

Can anyone advise how to get rid of that marks? When I try wiggling the saw to the left or to the right, there is no movement I can feel and the blade is tightened just fine.

Just in case that matters, my miter saw is Metabo KGSV 72 Xact SYM, and the blade is CMT 64 teeth for crosscutting with thin kerf (dont remember exact article).

Answer 1

I'm not an expert by any means, but that looks like the wood has scorched due to the friction of the saw blade. I know scorching can happen when making cross cuts if the wood and blade are not aligned properly (90 degrees from one another), if the speed at which you feed the wood is too slow (with a mitre saw, the speed at which your saw "drops" through the wood), or if the blade is dull and/or unclean.

On my miter saw, I have to check 90 degrees very carefully. Use a square, one side placed on the deck and the other against the saw blade. (This assumes your deck is level with the ground. It might be worth checking for this as well.) The drop should be absolutely smooth, i.e., you shouldn't have to "muscle the blade" at all to get your 90-degree cross cut.

While written about rip cuts, I think this piece is helpful as a starting point: What makes a rip cut burn.

Also, certain types of wood are more prone to scorching than others. For example, hard maple is very prone to scorching due to the amount of sugar in the wood and the hardness of the wood. It creates the perfect storm: slower to cut through and easily "caramelized" by the friction of the saw blade. Cherry suffers the same plight. While it has a high sugar content, pine varieties are so soft, a good saw blade runs right through it. You shouldn't be having problems.

Hope this helps!

Answer 2

the blade is CMT 64 teeth for crosscutting with thin kerf

You've established that the problem happens as the blade is spinning down, not when you're making the cut. I'd start by changing the blade for one with a standard kerf. With a thin kerf blade, the whole blade is thinner and less rigid. As the saw spins down after the cut, it passes through certain speeds at which the blade resonates, and a thinner, more flexible blade will vibrate more than a thicker, stiffer one.

Another option is to add a blade stiffener, which is basically a flat plate that rides against the blade and helps to keep it from vibrating. You can also get blade stabilizers, which are like a pair of precision made, oversized arbor washers that also help reduce vibration.