Planing boards

[gkas]

Recently I started on making another Paradise Box. The wood, birch, was 0.80" instead of 0.75". I didn't measure the thickness beforehand. Not wanting to chance planer snipe, I figured I'd just plane the boards down with a 0.5" bit. The bit I used was a downcut with a 20% stepover.. The surface came out quite smooth with no furrows or bit misalignment.

My question is that whenever I use this method, I get darker stripes. They do stubbornly sand out. I'm wondering if they're pressure marks like you get from milling around tabs. How do I prevent them? Use upcut bit? Smaller stepover? A very, very shallow last pass ? I'm using 90 degree raster with conventional cut.

[Rcnewcomb]

Can you post a photo?

[gkas]

I'll see if I can reproduce it today. I already sanded out the current project.

[bravesoul]

I have found that the spindle/router speed is too slow or your move speed is too slow. I plane quite a few boards on mine and have almost gotten it down with a few exceptions.

[ger21]

"Darker Stripes" may be burning. Try slowing down the spindle.
I think an upcut will give a slightly better finish, but the finish will never be as good as the finish from a planer.

[joeporter]

You may want to get yourself a card scraper (very cheap) and learn how to sharpen and use it after any machine planing. This will always improve the surface of your boards and bring them up to professional finish quality up to about a 180 grit paper with no snipe or planer marks. I then go on up to 320 or 400 grit and have a smooth as silk finish...joe

[martin54]

As ger21 says, good chance they are burn marks, especially if they are towards the ends of the board where the machine feed rate slows to turn round

[WaltS]

You may want to get yourself a card scraper (very cheap) and learn how to sharpen and use it after any machine planing. This will always improve the surface of your boards and bring them up to professional finish quality up to about a 180 grit paper with no snipe or planer marks. I then go on up to 320 or 400 grit and have a smooth as silk finish...joe

So I'm interested in this, as sometimes, and only sometimes, I will get some marks while surfacing a board. Not always, and mostly just on the end farthest from X,0. You can't even really feel them and they sand off, but, What exactly is a "card scraper"?

Edit - the marks are more like "ripples" if I had to describe them, not really dark or burn marks, but even that isn't the best description, but it's all I come up with a the moment.

[dealguy11]

"Card" scraper, also known as a cabinet scraper:

https://www.woodcraft.com/products/cabi ... 0-mm-thick

[WaltS]

Thanks!!

[gkas]

Here's a couple of shots of the same board. I ran 1/2" downcut @ 100IPM. I changed the spindle speed from 18,000 on the right to 13,000 on the left. These have both been lightly sanded. The slower RPM appears better. Both halves of the board felt smooth right off the table.

Now I'll dig up a 1/2" upcut or switch to a 1/4" bit.

[gkas]

And the answer is.... Slow the spindle and use an upcut bit. It looks like those were compression marks. This pic was the same batch of wood, same slower speed, same cut depth, same brand of bit (upcut instead of downcut). The piece was not even sanded. Still on the CNC.