Tips On Sanding
By Eric Knudsen
Heck, as long as you give your project a few good swipes with a palm sander, that should suffice, right? Wrong! In fact, there's a whole lot more to it than that. A poorly-sanded piece of woodwork will show every little flaw after a finish has been applied. Of course, by that point, it's too late. Unless you can live with the flaws, you'll have to start over. And no one likes to do that.
When it comes to sanding, there are a number of important steps you need to take to ensure that your woodworking project will look silky-smooth when it's all said and done. This is the final step in the woodworking process, and no amount of finish can hide a poorly-sanded project.
Even if you have an intermediate level of woodworking skills, you may find the following information quite helpful.
There are several different levels of sanding, as applied to woodworking:
- Rough Sanding: Tools used for this, are the belt sander, corded disc sander, and heavy sanding block (rigid). Used more often for basic construction; rough sanding can be used whenever a large amount of material needs to be removed --- but it shouldn't take the place of planing.
- Finish Sanding: Tools used for this include palm sander (w/ square sandpaper sheets), orbital sander (w/ round sandpaper sheets), stationery disc sander (bench-mounted), detail sander (uses small, triangular sandpaper pieces), rubber sanding block (using fine grit paper), and hand sanding (using whole sheets of paper).
- Touch-up Sanding: Whenever a piece of woodwork needs some very light, last-minute sanding attention. This is usually done by hand, or with a special detail sander using small pieces of fine grit sandpaper. Touch-up sanding is usually done just before a finish is applied.
- Hand Sanding: Often times, it's necessary to sand delicate areas and fine details of woodwork by hand, using nothing more than a sanding block, or just paper in hand. Hand-sanding is often preferred, when details must be crisp, or for getting at hard-to-reach-areas, like inside corners. Rough sanding (if needed at all) should be done at the outset of the woodworking project. Usually, this will occur before sections or pieces of a project are assembled, like when boards are rough, splintery, jagged, or are otherwise in need of attention.
However, rough sanding should not take the place of “planing”, as this is sometimes the mistake that less-experienced woodworkers make. If a wood surface has deep, numerous scratches and / or dings, it better to fill such blemishes with wood filler. While it's commonly thought it is best to sand wood surfaces with the grain, the rule isn't quite as rigid when applied to rough sanding, since the idea is to remove a good deal of material at once.
But keep in mind, it's still important to get as much of the rough sanding and intermediate sanding out of the way initially, to achieve reasonably smooth surfaces overall.
It is counter-productive to go through – 1) the rough sanding with coarse grades of paper--- and then, 2) the medium grade sanding, followed by 3) the finish sanding ...only to discover that you didn't do enough rough sanding initially. It can be very frustrating to reach the final stage of finish sanding, only to find that your project is still full of deep blemishes. You will probably find this out “the hard way”, unfortunately.
Clean the Wood Surfaces Between Sanding Stages
Practice with sanding over time will prove to be the best teacher. Take the time to look your project over carefully and closely between sanding stages and wipe the sanded surfaces well, using a tack cloth. Saw dust can accumulate inside of checks and crevices and sometimes “fool” the eye. Use a hog's hair brush or a soft-bristle shop brush to remove all of the sawdust. This will make the process of finish sanding go much easier.
Always try to sand in stages --- using coarser grits to take down heavy blemishes, and work your way up to the finer grits. Three stages of sanding is typical – starting with 80 grit paper, followed by 120 grit, and finishing up with 180 to 220 grit.
12 Helpful Tips on Finish Sanding
The bulk of most woodworker's sanding activities will be made up of finish sanding. The following information is a list of finish sanding tips you may find helpful:
- Besides rough sanding, you should always sand wood surfaces with the grain. Use long strokes and even pressure, when hand sanding and when using a palm sander. A common mistake for many beginners is to spend too much time in the same spot, which only wears down areas and makes the wood surface uneven. When using a palm sander, the trick is to keep the sander moving back and forth, in long, sweeping movements.
- Don't 'overuse' sandpaper! Sandpaper tends to clog up quickly and if the sand grains aren't removing material effectively, change the paper. For disc sanders and belt sanders, there's a product on the market that works like a giant “eraser” for removing clogged material --- it also looks and feels like a giant eraser. Sometimes called “the stick”, this special material is held against the surface of the sandpaper while the sander is rotating and pulls the clogged material free from the sandpaper --- the “stick” is inexpensive, and it works like magic! You can find this product at any well-stocked woodworker's supply store.
- Be extra careful whenever sanding outside edges and corners of woodwork, especially on soft hard woods like poplar and birch. It's real easy to “round-over' these edges, and the fine, square corners of your woodwork will be compromised.
- If you want to get a nice, even surface while sanding down the surface of a wide board, try making a bunch of light, zig-zagged pencil marks over the surface. Start out by using 80 to 120 grit sandpaper, working your way up to 150 to 220 grit. As you sand the face of the board, you'll see some of the penciled-in areas disappear, while others remain. Simply continue sanding, progressing with the finer grits of paper in stages, working until all the pencil marks are gone.
- When sanding in tight corners, try wrapping a small piece of sandpaper around the blade of a old, dull putty knife, a wooden shim, or an old ruler and tape it in place. When sanding inside convexes or shallow, rounded crevices, try wrapping the sandpaper around a piece of doweling rod, or similar material and follow the contour.
- Another trick for sanding unusual profiles is to take water putty, mix up a small amount, and press the mass of putty against the profile surface with wax paper in between. Let the putty harden, and pull the wax paper and putty away from the profile and then, wrap fine grit sandpaper around the hardened putty. You can make a custom made sanding block, made especially for any profile!
- When using a palm sander, the kind that takes 1/4 sheet of sandpaper, cut up several sheets of paper into quarters ahead of time --- that way, you won't need to stop every few minutes to cut up more squares. To make this process go quickly, make a simple jig, using a square piece of 1/2 inch plywood cut to 12” 's by 12” 's. Screw a 12” piece of 1 by 4 pine to one edge of the face of the plywood, so that it's dead even with plywood.
- Use the edge of the pine to square up and butt sandpaper sheets against, and cut two or three sandpaper sheets at a time. Use a heavy-duty utility (razor) knife to cut the sand-paper sheets. Some woodworkers take this simple jig a step further, by screwing a thin piece of metal to the plywood – the strip of metal is simply attached with a screw at two ends, and positioned in a way that the metal acts as both a measuring guide and a cutting blade --- set up a jig like this, and you'll never have to measure and cut sandpaper squares the old-fashioned way again!
- When sanding the edges of several boards of the same size and species (like for shelving units, cabinets, bookcases, etc.) you can make quick work of this task simply by clamping them all together, like a deck of cards. You'll not only do the job faster, you'll also maintain nice, square corners and edges, because the sander won't “wander” over the board edges.
- If the surface is to be stained, be sure that there's a compatible “stainable” wood putty available. Always test a wood filler product first --- before staining. For more on this subject, be sure to see the article on “Repairing Wood Finishes”, here at Shop Talk. Be sure to do your testing with the same species of wood.
- When sanding by hand with whole sheets of folded sandpaper, try this neat trick: Take some duct tape, and stick it to the backside of the whole sheet of sandpaper. This will essentially give you a flexible sanding sheet --- it will be more durable too, since the tape will keep the sandpaper from tearing. This works great for sanding large, rounded areas of wood surfaces.
- Buy the best-quality sandpaper you can afford. Cheap sandpaper never lasts -- it tends to fall apart and tear easily, and the sand grains just fall off, which can actually create more scratches! Using low grade sandpaper is actually counter-productive. Buy high-quality sandpaper sheets in bulk packages --- like packs of 50 to 100 sheets per box. You'll find quality sandpaper products at woodworker's supply outlets, and at some of the chain, home-improvement stores.
Remember, the sanding process is an important part of woodworking activity. A project that is sanded correctly will always look better than one that was poorly done.
And proper sanding will also ensure optimal bonding of the liquid finish, when applied to the wood surface.
So, don't slack-off on the sanding process. It's your project, and it will have your name on it. This is one area of woodworking where you don't want to cut corners.
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Eric Knudsen is a freelance writer and former restoration contractor, living in Upstate New York.
