Poor saw cuts, machine fault or wood?

[Nyfiknast]

Hello

I'm working on cutting a staircase from 120mm decking, and when the upright boards need to be mitered at 45°C, it doesn't turn out well. I'm attaching a picture.
I've tried tilting the saw 45°C and cutting from both the right and left with the same result. After that, I tried cutting the board on its edge from both directions, but it was the same thing there.
The board is clamped by a clamp on the saw, and the part that hangs outside rests on a table to avoid it hanging freely.

The saw is a Makita LS1018L from 2016 with a cutting depth of 91mm (in reality, it manages a few millimeters over 95mm).
I was bothered at purchase by it wobbling on startup, which was solved by removing all washers and saw blade, cleaning, lubricating, and swapping the washers and rotating the blade 180°C.
The blade was replaced with a Makblade Plus quiet cutting 260mm 60T.
The machine is calibrated with a square and has cut well before...

 

[13th Marine]

Doesn't it become like that when the board is cupped?

 

[Nyfiknast]

Doesn't it get like that when the board is cupped?

I've thought about that too and wonder, in that case, how do all those who build something with 120mm decking do? All the lumber I have and that was available at byggmax is like that? :/

 

[Tosse]

The timber will still move so much later... the perfect miters aren't perfect for very long. Even the cupping will change.

 

[MathiasS]

The timber will move so much later on... the perfect miters aren't perfect for long. Even the cupping will change.

And?

If you don't have higher standards than that for the saw, you might as well just snap the wood pieces over your knee, roughly where you want them cut.

Obviously, there's something wrong with the machine; it's not due to any potential cupping of the board (which would only be evident when the board has straightened out or cupped compared to its state at the time of cutting).

 

[13th Marine]

I think as I said the board is cupped, that's what happened with my miter saw when I cut cupped boards...

 

[nimhed]

13th Marine is right. If you angle the blade at 45 degrees and saw through a cupped board, it turns out like that.

So there’s nothing wrong with the saw.

 

[MathiasS]

...except that the plank doesn't have a 45-degree cut then.....what are your thoughts?

 

[nimhed]

Sure. The plank is cut at 45 degrees. It just doesn't show from that angle.

 

[Tosse]

And?

If you don't have higher demands than that on the cuts, you might as well just snap the wood pieces over your knee, roughly where you want them to break.

Obviously, something is wrong with the machine; it's not due to possible cupping of the board (which would reveal itself when the board straightens or cups compared to its position during cutting).

And?

Of course, it's due to the cupping. How else do you think a rotating saw would cause that? It would require moving the fence or the workpiece during the cutting.

 

[kashieda]

You wrote that you turned the record. Do you mean that it's spinning backwards now?

 

[slacker]

Place a square or the back of a saw against the timber and you'll probably see what the problem is - I agree with the others, the timber is warped, which is why all your 45-degree cuts turn out this way.

 

[prototypen]

If we got to see the board angled 45 degrees with a try square against the sawn surface.

Protte

 

[MathiasS]

Sure. The plank is cut at 45 degrees. Just not visible from that angle

In that case, the conclusion is fine.