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Woodworking Tips from Gregory Paolini |
| Information, Tips, and Know-how for woodworking Enthusiasts |
Sanding 101: The best finish starts long before you brush anything on.
Text & Photos by Gregory Paolini
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A silky smooth work piece is the goal of most woodworkers. We want to touch a finished chair, or table, and have our hands glide along a glass like surface. Some woodworkers try to accomplish this by adding more and more coats of finish, and in the process, defeat themselves. The key to a great finish, is to begin by removing what's under it, by sanding. | |
| When you're sanding, you're actually smoothing rough wood by removing some of it. You start off with coarse grits of sand paper which make deep scratches, and then step up to finer and finer grits which are able to remove the scratches left by the previous, coarser grit papers. Eventually we finish with a surface which our fingers and hands perceive as smooth.. | ||
| The Most Common Mistakes | ||
| A lot of woodworkers dread sanding, because it takes so much time. And it does, but for some woodworkers, sanding takes a lot more time than it needs to. | ||
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The purpose of sanding is to smooth wood, not shape it. If you have a shape or curve, remove materials with more aggressive tools before you think about sanding. Relieve edges with block planes, or files. Use a pattern makers rasp to refine a curve. The point is, to identify smoothing versus shaping, and use the appropriate tool for the task. | |
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various sanders |
Don't make the mistake of trying to attain the perfect surface when starting off with your coarsest grit. The more rough scratches you add, the more you'll need to remove later, which means you've just doubled your sanding time. The goal of any stage of the sanding process is to smooth the surface only enough so that you can move on to a finer grit. | |
| As with any other tool in your shop, sand paper removes material. You can't put back any of the wood you sanded off, but you can always come back to remove a little more if you need to. | ||
| My sanding schedule | ||
| Before I begin sanding a piece, I like to think about what kind of finish I'll be using on it, as well as what kind of wood I'm working with. Will I be applying a thin oil finish, such as tung or linseed oil to a piece of cherry? Or will I be spraying on several thick coats of acrylic on oak, which tends to fill the grain, and cover the wood with a blanket of plastic? My schedule, or series of grits that I use will vary depending on the circumstances. | ||
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If my jointer or planer blades are dull or chipped, there will be tell tale ridges left on the wood, and I'll begin with a quick 80 grit pass, just to level the surface. But if my tools are in tip top shape, I generally begin sanding with 100 grit paper on a random orbit sander, regardless of what kind of wood I'm working with.. |
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a random orbit sander makes quick work of tedious sanding |
Don't press down on the sander, just let the weight of the tool do the work. And the speed at which your sander moves along the board should be about one inch per second. This will allow the sander to create a great random swirl pattern | |
| Again, regardless of what type of wood I'm working with, I'll repeat the process with 120 grit, then 150 grit paper. Make sure you blow off the work piece between grits with compressed air. You don't want to leave any 120 grit size abrasive on the wood as you move up to 150 grit, or you'll be left with 120 grit scratches. If you don't have a compressor, you can vacuum the work piece to accomplish the same thing. | ||
| Time to Stop? | ||
| In some cases, yes. If I'm working with a coarse grain wood, such as oak, walnut, or mahogany, and I plan to apply a thick film finish such as polyurethane, or acrylic, I'll stop at this point. The thick film finish will fill some of the grain, and build up to a point where it creates a nice smooth surface. | ||
| If I intend to apply a stain to any of these woods, I'll do one more round of sanding at 180 grit. Oil based stains have heavy pigments which tend to collect in sanding scratches, highlighting the small swirls left from the random orbit sander. Sanding to 180 grit leaves scratches small enough that the stain doesn't collect in them. | ||
| 180 grit is also a good point to stop at if you're applying a polyurethane or varnish to a fine grain wood, such as maple or cherry. | ||
| If I'm applying a wipe on finish, or a thin oil finish, such as tung oil or linseed oil, I generally sand one more stage at 220 grit. Wipe on finishes, and pure oil finishes have very thin, or no build at all, and you must rely on the wood for tactile satisfaction. | ||
| Wrapping things up | ||
| While I've touched on finishing, the purpose of this article is not to instruct you on how to finish - I need other things to write about in the future. But you need to consider your finish before you sand. | ||
| Keep in mind, regardless of how you plan to finish, the wood should be pleasing to the touch when you're done sanding. | ||
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Now let's make sawdust!
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| For your safety: Woodworking is inherently dangerous. Failure to use power or hand tools properly can cause permanent injury or even death! The information provided here is not a substitute for formal instruction or education. Do not try anything you learn here unless you are absolutely certain it is safe for you to do so. If there is an aspect of woodworking you are uncomfortable with, do not do it! Be sure to read any and all manuals and safety instructions which come with your tools, and always wear appropriate safety equipment. |
