Wood finishing: what’s causing/how do I avoid these lines in my projects?

General Questions
#1

These are two different projects with similar issues.

The cutting boards started out as rough-cut slabs of walnut and maple. Among other things, they went through a Delta jointer, then a Powermatic planer and then sanded with a Milwaukee ROS (generally moving only with the grain direction). I started with 80-grit and moved to 120, 150, 180 and 220. Between each grit I used a sanding block (again with the grain) wrapped with the corresponding grit. They were finished with Butcher Block Conditioner, and you can see faint, diffuse lines that run perpendicular to the grain.

The other project is a plant stand top (I only took pictures of the back). There, I started with dimensional lumber from Lowes (red oak). I sanded it with a Makita ROS with the same progression of grits and same mid-grit hand sanding. It was finished with a MinWax oil-based stain. You can see somewhat sharp lines that run perpendicular to the grain.

Any idea what I’m doing to put the lines in? How to avoid them or remove them before finishing? And how do I know they’re still there or gone before I start finishing?

#2

Those are saw-marks from the mill.
The only way I know to get rid of them is to sand (or plane) below them, which could be time consuming…

#3

That would be my guess, as well. They can be deceptively deep and a PITA to remove. I’d suggest trying to take them out using either a cabinet scraper or a card scraper that has been properly edged.

#4

Most craftsmen use a scraper for final finishing of the surface. It’s labor intensive and takes more talent than sanding, but it avoids problems like I think you’re describing.

It’s not as easy as they describe. (It never is)

#5

Probably saw marks. Possibly some over-aggressive power planing if it’s directly across the grain. According to some those marks would fade after the wood cycles through increasing and decreasing humidity before finishing so the compressed grain evens out. Anyway, it doesn’t look bad, you’ll notice it a lot more than anyone else.

#6

I never find a ROS is capable of taking planer marks or other blemishes out of wood. As my old woodwork master liked to joke - all you end up with is smooth bumps. We were taught to use a hand plane to smooth the surface. It takes some skill and care, and if there is cross grain it is almost impossible to do without ripping the surface somewhere. Which is where a scraper can be a saviour. You need a long plane, and these are not cheap if you want a good one.

#7

These look like planer marks to me.

How sharp are your planer blades? How aggressive is your feed? Two light passes are better than one heavy one.

#8

Depends entirely on how you tune it. You can put as aggressive a ‘hook’ on it as you wish, depending on how much material you want to remove. A scraper can also give a smoother finish than sandpaper, if done properly. I know master woodworkers who rarely do more than a cursory sanding, preferring well tuned blade tools instead.

#9

Thanks!

I’d rented space in a shop for the first project. They had changed the knives in the planer within the past couple months; I don’t know if they were sharpened in between. I am new to the equipment, so can’t yet tell on my own how aggressive my passes were. I did try to make smaller steps between, but only experience will give me the right feedback.

Just went to a woodworker’s expo a week or two ago and spent some time at the Veritas booth. Beautiful tools. Pricey though, so they’re somewhat off in the future (just about done saving for a Sawstop; next is a jointer/planer). I do have basic bench and jack planes and need to learn how to use them — and it looks like a scraper set is in the short-term basket.

#10

Along with the scrapers, you’ll need a good flat file, a diamond stone and a burnishing tool for tuning them up. There are scads of YouTube vids about how to tune one up, but you don’t need to make any sort of special jigs. Just remember to clamp the file or the stone (not the scraper) in your bench vise. By clamping the file in the vise and drawing the scraper across it, you’re guaranteed a 90 degree angle; other way round, not so much.

I bought a Veritas card scraper holder, and it’s been nearly worthless. A scraper can be hard on your hands, but a cheap pair of work gloves solves that problem. You really need the control that just your hands give you.

The key to using any plane is a blade made from good steel that is kept razor sharp, and an absolutely flat sole plate. I highly recommend Hock blades, if you’re not familiar with them. The nice part about this company is that when you call for help, more likely than not Ron Hock will answer the phone and talk you through it.

#11

The trick to a smooth finish is in the grit that you BEGIN sanding with. The trick is to make sure…doubly sure… that you get all the saw marks out with the coarsest grit that you use. If you begin with 80 grit and notice that you are still seeing scratches then go to 60 grit. Once you have thoroughly sanded the workpiece, then progress to the next finest grit. Sand each grit thoroughly. You will find that if you have sanded thoroughly with the course grit, then each progressively finer grit will go very quickly.

Once you get to about 220 you can try trick no. 2. Wet a cloth and wipe the surface and let it dry. This raises the grain and you can proceed to 320, 400, and even 600 if desired. When using a random orbital sander there are a number of things to look for.

One, make sure the pad is in good condition and has not softened to where the screws which hold the pad on protruding enough to mar the workpiece. It can happen easier than you think.

Next, let the sander do the work. Don’t try to press down on the sander. You will, to a degree, anyway, but don’t press down excessively. Your job is just to guide the sander.

Also, if you notice, there are holes in the sanding discs which should correspond with holes on the pad of the sander. These holes are a means for the dust to be extracted. If they don’t line up… at least somewhat… the dust will not be removed as efficiently and will reduce efficiency.

Not to be critical but red oak is not the best choice for cutting boards. The reason is that oak, while strong, has very large and numerous pores. Food bacteria can get into these pores and they will have a party there. Woods like maple, walnut, cherry, purpleheart would be a better choice.

As for finish, I have always used mineral oil. You can buy it at the grocery or drug store and it is cheap. Apply liberally until the wood will not absorb any more, then a mineral oil/beeswax blend.

#12

Again, thanks.

The cutting boards were maple/walnut; the plant stand is red oak (I’ll post a finished image if it comes out marginally well and I don’t end up back at the drawing board).

What’s good to use mid-sanding to check to see if the lines are gone? Is plain water good enough to highlight any unwanted residual markings? Would a spirit or oil (what’s the difference?) work but only if I’m planning on using an oil-based stain/finish? Or if it’s put on light enough early in the process it won’t make a difference?

#13

A drum sander is useful here. You can take several passes with a coarse grit before the finishing steps. Helical planers don’t cause as much of a problem, at least the marks aren’t as obvious.

#14

I keep a spray bottle of water in my shop just for that purpose. A light mist, then wipe with a paper towel, so you don’t have to wait forever for the water to dry. Use a pencil to mark any areas that need work, including tear-out areas that you may not even see when dry.

Not to be contrary, but the notion of using very coarse sandpaper doesn’t sit well with me. Paper that coarse will actually introduce new scratching that will need to be sanded out with the finer grits. You are much farther ahead of the game if you can learn how to effectively use your blade tools. The nice thing about card scrapers is that they can be used on curved surfaces, also.

#15

The best thing to use is a good light and perhaps some magnifier glasses if your eyes are old like mine. You could do a wipe down with denatured alcohol or mineral spirits (I would not use mineral spirits on cutting boards). Look closely and you will be able to see if any scratches are left over from the prior grits. Get your sanding done before any final finish is applied.
The problem with sanding is simply this… many times a person goes to a finer grit too soon. Like I said earlier, the better you complete the coarsest grit, the easier the following grits will be.

Mineral spirits and denatured alcohol will quickly vaporize with no residue. Oil will not.