Woodworker's Journal 2011-35-Winter, страница 19
Step Four, the final sanding step is simply to straighten out the 180-grit scratches. The quickest way to do that is to use the same grit paper. Only this time, I switch to garnet paper and sand with the grain until the diagonal 180-grit scratches are gone. In most cases, 180-grit garnet will leave the surface smooth enough to finish, but some very hard woods, like boxwood or ebony, may require finer sanding steps. If you can still see obvious and offensive scratches in these very hard woods, continue sanding to 220- or even 320-grit. Sanding by Machine To put it bluntly, sanding by machine is easier than sanding by hand. The same rules still hold though, with some minor exceptions. To flatten or shape wood with a belt sander, run it diagonally to the grain just as you would with a block. Be careful, though. Belt sanders can be aggressive and are not really the right tool for finish sanding. Vibrating or random orbit hand sanders, either electric or air powered, are a better choice. They cut by rotating in tiny circles, so what direction you move the machine in is irrelevant. It is always cutting more or less across the grain. For that reason, they are great for all sanding steps except the final Hand sanders are meant to be moved only about 1" per second. Moving the sander too fast or "scrubbing" will also cause pigtails. If you want your piece to stain evenly, sand it uniformly. The left side of this board was sanded only to 120-grit, and the right side to 180. The same stain wiped across both resulted in two different intensities of color. Always read the back of your sandpaper. It will provide the information you need to make good sanding choices. pass, which should be done by hand, with the grain, and if possible, with garnet paper. The one problem associated with these is "pigtails," small curlicue scratches that show up only after you have stained or finished. The secret to avoiding pigtails is to lighten up and slow down — literally. Don't press down on the sander or it will slow down the speed of the head, causing pigtails. Use only the weight of the sander itself along with the weight of your hand. And move it slowly. Moving the sander too fast or "scrubbing" with it will also cause pigtails. Hand sanders are meant to be moved only about 1" per second. This page is about 11" long. Try moving your hand as if you were sanding so that it takes 11 seconds to get from top to bottom. Slow, isn't it? But if you move your sander like that, you won't get pigtails, and you'll need to sand each area only once per grit without going back over it. I know it is frustrating, but calm down and daydream when you sand and you'll get a better job. As I said, lighten up and slow down. Sanding Media Using the right stuff also contributes to quick results. The problem is that store shelves are littered with different types and configurations of sandpaper. Sorting them out can be confusing. Start by turning your sandpaper over and reading the back. Inside a double line is the manufacturer's name. (Here, it's 3M™.) Below that is the information box, starting with 110N, the manufacturer's product number. Then comes the nitty gritty. continues on page 20... winter 2011 19 |
